Embed Size (px)
Citation preview
DEGREE PROJECT INCIVIL ENGINEERING AND URBAN MANAGEMENTSTOCKHOLM, SWEDEN 2018
Designing Roller compacted concrete (RCC) dams
SHAYMA AL BAGHDADY
LINNEA KHAN
KTH ROYAL INSTITUTE OF TECHNOLOGYSCHOOL OF ARCHITECTURE AND THE BUILT ENVIRONMENT
Designing Roller compacted concrete (RCC) dams
SHAYMA AL BAGHDADYLINNEA KHAN
Master of Science ThesisStockholm, Sweden 2018
TRITA-ABE-MBT-18366, 2018
ISBN 978-91-7729-869-4
KTH School of ABE
SE-100 44 Stockholm
SWEDEN
© Shayma Al Baghdady & Linnea Khan 2018Royal Institute of Technology (KTH)Department of Civil and Architectural EngineeringDivision of Concrete Structures
i
Abstract
Concrete is the most common building material in the world and it consists of aggregates, cement and water that harden over time, it is also known as a composite material. The use of concrete is very versatile due to its resistance to wind and water and its ability to withstand high temperature. These qualities make concrete a suitable building material for large structures such as dams.
A dam is a huge construction that needs massive amount of concrete to build it with and that leads to high cost, so alternative methods should be considered to minimize the cost of constructing the dams. One method is building the dams with Roller Compacted Concrete (RCC), which by definition is a composite construction material with no-slump consistency in its unhardened state and it has achieved its name from the construction method. The definition for a no-slump consistency is a freshly mixed concrete with a slump less than 6 mm. The RCC is placed with the help of paving equipment and then it is compacted by vibrating roller equipment. The RCC ingredients are the same as for the conventional concrete but it has different ratios in the materials that are blended to produce the concrete. It differs when it comes to aggregates because both similar aggregates used in conventional concrete or aggregates that do not fulfill the normal standards can be used in the RCC mixtures. This means, for example that aggregates found on the construction site can be used for the RCC.
Compared to when constructing a conventional concrete dam, which is usually built in large blocks, the RCC dam are usually built in thin, horizontal lifts, which allows rapidconstruction. This reduces the amount of formwork, but also the demand for man-hours are less due to the usage of machines for spreading and compacting, ultimately making it a cheaper method. Building with RCC has become very popular around the world because of its advantages and new methods have been developed over the past two decades, adapted to the experience gained after each project. All RCC dams that has been built, usually faces challenges both during and after construction, and it includes everything from temperature variations, cracks to leakage.
The main purpose of this master thesis is to create a guideline for how to design and constructdams with RCC and the idea is to be able to use it as a basis for future dams. The requirements of Eurocode 2 and RIDAS are the basis of the criteria that the dam must fulfill and information of what is expected of the RCC is presented in this thesis. Furthermore an example for design of an existing embankment dam to an RCC dam has been presented in this thesis. The embankment dam needs to be rebuilt in order to increase the safety of the dam and the goal of the case study was to determine the dimensions of the new RCC dam.
Keywords: Roller Compacted concrete, Massive concrete structures, Dams, Concrete
iii
Sammanfattning
Betong är det vanligaste byggmaterialet i världen och det är ett material som består av ballast, cement och vatten som härdas över tiden, även känt som ett komposit material. Användningen av betong är mycket mångsidig tack vare dess motståndskraft mot vind och vatten och dess förmåga att motstå höga temperaturer. Dessa egenskaper gör betong ett lämpligt byggmaterial för stora strukturer som dammar.
En dam är en enorm konstruktion som kräver massiva mängder av betong för att bygga den med och det leder till höga kostnader, därför bör alternativa metoder övervägas för att minimera dessa. Ett förslag till en metod är att bygga dammar med Roller Compacted Concrete (RCC), som per definition är ett komposit material med ett sättmått på mindre än 6 mm i sitt ohärdade tillstånd. RCC har erhållit sitt namn från sin byggmetod, då den sprids med hjälp av utrustning för att lägga vägar och sedan kompakteras den med en traktordriven vibratorvält. Ingredienserna för RCC är samma som för konventionell betong, men den stora skillnaden utgörs av att det är olika mängd-förhållanden av de material som blandas för att producera denna betong. Det skiljer sig också när det gäller ballasten, eftersom både liknande ballast som används i konventionell betong eller ballast som inte uppfyller de normala standarder kan användas för RCC. Det betyder att exempelvis, ballast som man erhåller på byggarbetsplatsen kan användas för att producera RCC.
I jämförelse med när man bygger en traditionell betongdamm, som vanligen byggs i stora block, så bygger man oftast en RCC damm i horisontella lager vilket ger möjligheten för snabbt byggande. Detta reducerar behovet av att använda gjutformar, men även antalet mantimmar på grund av användningen av maskiner för spridning och kompaktion. De här faktorerna gör det till en billigare metod. RCC dammar har blivit populärt att bygga runt om i världen på grund av dess fördelar och nya metoder har utvecklats under de senaste 20 åren anpassade efter erfarenheten man har erhållit efter varje projekt. Alla RCC dammar som byggts stöter ofta på utmaningar både under och efter byggandet och det har med, allt från temperatur variationer, sprickor, och läckage, att göra.
Huvudsyftet med det här examensarbetet är att skapa en guide för hur man designar ochbygger en RCC damm och tanken är att man ska kunna använda den som en grund för framtida dammbyggen. Kraven från Eurokod 2 och RIDAS är grunden för kriterierna som dammen ska uppfylla och information om vad som förväntas av RCC är presenterat. En fallstudie har gjorts, där ett exempel på en design för en RCC damm som ska ersätta en befintlig fyllningsdamm i Hylte är presenterad. Fyllningsdammen är i behov av ombyggnation för att höja säkerheten av dammen och målet med fallstudien är att avgöra dimensionerna för den nya RCC dammen som ska placeras där.
Nyckelord: Vältbetong, Massiva betong konstruktioner, Dammar, Betong
v
Preface
This is a Master of Science thesis written at the Division of Concrete Structures, Department of Civil and Architectural Engineering at KTH Royal Institute of Technology during the period of January-June 2018. Dr. Richard Malm, KTH, supervised the thesis subject.
We would like to thank Dr. Richard Malm for the support and guidance he has given us during this period. We would also like to express our gratitude to adj. Erik Nordström for providing us with guidance and material for our case study.
Stockholm, June 2018
Shayma Al Baghdady & Linnea Khan
vii
Contents
Abstract ...................................................................................................................................... i
Sammanfattning ...................................................................................................................... iii
Preface ....................................................................................................................................... v
1 Introduction...................................................................................................................... 1
1.1 Background ............................................................................................................. 1
1.2 Purpose and limitations ........................................................................................... 4
1.3 Scope of the thesis ................................................................................................... 5
2 Roller compacted concrete (RCC) and dams ................................................................ 7
2.1 Definition of RCC ................................................................................................... 7
2.2 Material ................................................................................................................... 8
2.2.1 Selection of material................................................................................... 8
2.2.2 Mixture proportions.................................................................................. 11
2.2.3 Properties of hardened concrete ............................................................... 18
2.3 Construction .......................................................................................................... 32
2.3.1 Foundation considerations........................................................................ 32
2.3.2 Construction method ................................................................................ 32
3 Challenges during construction.................................................................................... 39
3.1 During construction ............................................................................................... 39
3.2 After construction.................................................................................................. 40
3.3 Construction of existing dams............................................................................... 42
3.3.1 Upper Stillwater ....................................................................................... 42
3.3.2 Willow Creek ........................................................................................... 43
4 Design of new RCC dams.............................................................................................. 45
4.1 Design criteria ....................................................................................................... 45
4.2 Loads ..................................................................................................................... 46
4.3 Loading combinations ........................................................................................... 47
viii
4.3.1 Load cases for calculation of stability...................................................... 47
4.3.2 Load cases for cross-section analysis....................................................... 48
4.4 Design of cross-section ......................................................................................... 49
4.4.1 Load values and combinations ................................................................. 49
4.4.2 Material values ......................................................................................... 52
4.5 Stability conditions................................................................................................ 53
4.5.1 Safety against sliding, μ ........................................................................... 53
4.5.2 Safety against overturning, s .................................................................... 55
5 Case study....................................................................................................................... 59
5.1 Background ........................................................................................................... 59
5.2 Calculation & CADAM......................................................................................... 60
5.3 Results ................................................................................................................... 60
6 Conclusions..................................................................................................................... 63
6.1 Discussion ............................................................................................................. 63
6.2 Future studies ........................................................................................................ 64
Bibliography ........................................................................................................................... 65
A CADAM & calculation ................................................................................................ 69
1
1 Introduction
1.1 Background
Concrete is the most common building material in the world and it is a composite material. It consists of a mixture of coarse aggregates, water and cement that hardens over time. The use of concrete is versatile due to its resistance to wind and water and its ability to withstand high temperature (PCA, 2018). These qualities make concrete a suitable building material for large structures such as dams and hydropower plants.
The main reasons for building dams in today’s society are water supply, irrigation, flood control, navigation, sedimentation control and hydropower. Most of the dams that have been constructed are single-purposed, where irrigation and hydropower are the most common ones.There are also multipurpose dams, which are increasing in number especially in developing countries. The importance of these projects for the developing countries is a great deal, due to a single investment contributes to economic and domestic benefits for the population. (ICOLD, 2017)
There are different types of dams, and in Sweden the most common ones are embankment-and concrete dams, see Figure 1.1. Embankment dams are typically referred as “rock fill” or “earth fill” dams depending on the material used. Commonly used materials are natural rock, soil or waste materials which are obtained from mining operations. Concrete dams are categorized in three common types: arch, gravity and buttress. See Figure 1.2, 1.3 and 1.4.The main difference is the way they are designed. The arch dam is somewhat thin in the cross-section and it resembles a part of an ellipse or a circle. The gravity dam is built up of vertical concrete blocks that are joined together by seals in the joints. The buttress dam is also vertical concrete blocks but with reduced concrete mass. (ASDSO, 2017)
Figure 1.1 Example of an embankment dam, consisting of (1) clay, (2) a drainage layer, (3) gravel, (4) (5) stone, and (6) a drainage well. (Vattenkraft.info, 2009)
2
Figure 1.2 Gordon Dam, Tasmania, an arch dam. (Wikiwand, 2018)
Figure 1.3 Grand Coulee dam, Washington, a gravity dam. (Wikiwand, 2018)
3
Figure 1.4 A buttress dam in the village Rätan. (Vattenkraft.info, 2009)
A concrete dam is a large construction that needs massive amount of concrete, resulting in the use of a large amount of cement. This leads to both a high cost and a negative impact on the environment due to CO2 emissions from cement production. Therefore alternative methods should be considered to minimize the cost of constructing the dams and to minimize the use of cement. One method is building the dams with Roller Compacted Concrete (RCC), which is a concrete that is compacted by vibrating roller equipment. RCC ingredients are the same as the conventional concrete but it has different ratios in the materials that are mixed to produce the concrete. It is known for its rapid construction method. An example of an RCC dam is shown in Figure 1.5.
4
Figure 1.5 dam
1.2 Purpose and limitations
The purpose of this Master thesis is to develop a guideline for how to design and construct a roller compacted concrete dam in Sweden, which may be of use in the future. This thesis will bring all the basic knowledge needed about RCC and bring up critical parts for when designing a dam. The research questions that have governed this thesis are:
What are the differences in design of conventional concrete dams and roller compacted dams?Would it be possible to build a roller compacted dam in the Sweden, taken into account the cold Swedish climate?Which design standards are used for RCC dams internationally?
This thesis will not include a life-cycle analysis; however, it will be discussed how CO2 emissions from RCC affects the environment. A life-cycle cost will not either be consideredin this thesis. The case study, which is performed in this thesis, will not include a cross-section analysis. It will only consider stability calculations.
5
1.3 Scope of the thesis
This thesis begins with a theory chapter, Chapter 2, which provides what materials are chosen and used; along with what properties are expected for the roller compacted concrete.
Chapter 3 brings up the typical challenges with this type of dam during and after construction, giving example of dams that had similar challenges.
Chapter 4 constitutes the design of the roller compacted concrete, with criteria’s of the cross-section and stability presented from Eurocode 2 and RIDAS, which is the Swedish guideline for dam safety.
Chapter 5 constitutes the case study, where a dam is designed, with the help of stability calculations, on a given topography.
Chapter 6 the discussion is presented, bringing up the possibility of constructing RCC dams in Sweden.
Chapter 7 presents the proposed future study.
Appendix A provides the full calculations that were made for the case study in Chapter 5 and the inputs in CADAM.
6
7
2 Roller compacted concrete (RCC)and dams
2.1 Definition of RCC
Roller compacted concrete, also known as RCC, is a composite construction material with no-slump consistency in its unhardened state. It has achieved its name from the construction method where the RCC is placed with the help of standard or high-density paving equipment and then it is compacted or consolidated with rollers. The definition of a no-slump concrete is a freshly mixed concrete with a slump less than 6 mm, where the slump is the difference between the height of the mould and the highest point of the specimen, see Figure 2.1 (Maxi, 2017).
Figure 2.1 The consistency of the concrete is tested with the help of the slump test (Maxi, 2017)
This consistency allows that the following lifts can be placed directly after a previous lift has been compacted. Compared to conventional concrete, the materials that are used for the RCC are usually of a wider range. When mixing the RCC the philosophy is to use adequate paste volume to fill the aggregate voids, without using more water than is needed for a decent workability. (USACE, 2000)
The hardened RCC and conventional concrete have similar properties, when it comes to durability, and RCC can therefore be used for building dams. Constructing RCC dams has become immensely popular throughout the world due to the advantages it comes with. The main advantages are the rapid construction process, reduced costs and smaller environmental impact due to less cement. (ACI, 2011)
8
2.2 Material
2.2.1 Selection of material
2.2.1.1 Cementitious materials
Cement is one of the key components in concrete production and the most used type is the Portland cement. Cement consists of a mixture of limestone and clay which is then heated, producing a substance called “clinker” that contains calcium, silicate, alumina and iron oxide(PCA, 2018). There are different types of cement depending on the concretes application and these are listed in Table 2.1.
Table 2.1 Types of Portland cement and their general features (Jennings H et al., 2010)
Portland cement type Description Applications
Type I Normal General construction (most buildings, bridges, pavements, pre-cast units etc.)
Type II Moderate sulfate resistance Structures exposed to soil or water containing sulfate ions.
Type III High early strength Rapid construction, cold weather concreting.
Type IV Low heat hydration (slow reacting)
Massive structures such as dams. (Nowdays rare.)
Type V High sulfate resistance Structures exposed to high levels of sulfate ions.
When selecting type of cement for RCC and conventional concrete, some factors must be taken into account such as; the quality and the type of the cement, how it reacts with pozzolan, the manufacturer’s capability to deliver sufficient quantities and the delivery cost to site.
The most commonly used cement in the RCC mixture is the type II due to the low heat generation at early ages and the longer set times, which may lead to control or reduction of thermal cracking. Generally for cements with low heat generation, the development of strength is slower than e.g. for cements of type I and type III. (USACE, 2000)
Cement in RCC mixtures can be partially replaced with pozzolan for the following reasons(ACI, 2011):
1. To reduce heat generation;2. To reduce costs;3. To be used as supplemental fines in the mixture;4. Reduce CO2 emissions.
9
Natural pozzolans and fly-ash are example of different types of pozzolans. According to SSEN 206, the amount of pozzolan in a RCC mixture can vary from none to up to 25% byvolume depending on the exposure class. There are different ways to add the fly ash, either during the production of cement or it can be added directly to the concrete mixture. There are two methods the fly ash may be added, if it is added directly to the concrete mixture: the k-value concept or EPCC.
According to ASTM C618 (2018), pozzolans are classified into three categories shown and described in Table 2.2.
Table 2.2 Classes of pozzolan, according to ASTM C618 (2018)
Class Description
N Raw or calcined natural pozzolan
F A low-calcium fly ash
C A high-calcium fly ash
Class F fly ash is the used pozzolan in both RCC and conventional concrete, and it gives the concrete enhanced properties such as decreased permeability and thereby higher seepage control. It has also the ability to control the heat gain effectively as well as it provides resistance against sulfates and sulfides. (Headwaters Resources, 2017)
2.2.1.2 Aggregates
Aggregates can be obtained from excavations for the dam or from rock quarries. The quality and the grading of the aggregates have a great effect on the properties of the RCC. The grading influences the workability of the mixture, the total void ratio and the capability to efficiently consolidate or compact the RCC. (USBR, 2017)
The common nominal maximum size, also known as NMSA, of coarse aggregate particles can vary from project to project, but usually 25 mm has been used to prevent segregation during transportation, spreading and compacting. However, there are projects that has used up to 75 mm sized coarse aggregate. On the other hand, for fine aggregates the preferable size iscommonly 75 μm for RCC with low cementitious material content, (USACE, 2000). Typical grading curve that may be used for aggregates in RCC is shown in Figure 2.2.
Too great amount of fine aggregates may cause a reduction of the workability, demand for more water, followed by a loss of strength. If plastic fines are used in the mixture, it is of great importance that an analysis of durability is made. This will determine, from a practical point of view, how to meet the structural design requirements. (ICOLD, 2003)
10
Figure 2.2 Suggested combined aggregate grading with coarse and fine aggregate gradation bands
In Sweden, the aggregate standard is governed by the Swedish Standards Institute and the aggregates are with high quality which results in concrete with good strength properties.
2.2.1.3 Chemical admixtures
There are two types of admixtures that are commonly used in RCC mixtures: water-reducing admixtures and air-entraining admixtures.
According to ASTM C494 (2018), the chemical admixture is categorized in to eight types, all described in Table 2.3, depending on the desired properties of the RCC mixture.
Table 2.3 Types of admixtures, according to ASTM C494 (2018)
Type Purpose
A Water-reducing admixture
B Retarding admixture
C Accelerating admixture
D Water-reducing and retarding admixture
E Water-reducing and accelerating admixture
F Water-reducing, high range admixture
G Water-reducing, high range and retarding admixture
S Specific performance admixture
11
The most commonly used admixture is type D, which gives increased workability of RCC and longer setting times. (ACI, 2011)
The air-entraining admixture is added to create small bubbles of air uniformly through the RCC, as well as in conventional concrete. The benefit of this admixture is that the concrete gains damage resistance when it is exposed to repeated cycles of freezing and thawing when saturated. It is on the other hand not commonly used in RCC, because it is hard to create the voids of the proper size and distribute it evenly due to the no-slump consistency. However, if this type of admixture is to be used, a Vebe time (see Section 2.2.2.3, Figure 2.5) less than 20 seconds is typically required. (ACI, 2011)
2.2.2 Mixture proportions
2.2.2.1 RCC mixing
The mixture proportioning procedure for RCC and conventional concrete are about the same, except that for RCC, some differences due to no-slump consistency and the relatively low water content can appear. The consistency RCC has to be sufficiently stable to tolerate the vibratory roller’s weight and other heavy machines, but at the same time, it must have sufficient workability to fill up the voids between the aggregate particles with mortar or paste during the compaction. (ACI, 2011)
The main difference between the RCC and conventional concrete is the ratios of the components which are represented in Figure 2.3 and 2.4 below. It also differs when it comes to aggregates because RCC mixtures can use similar aggregates used in conventional concrete or aggregates that do not fulfill the normal standards. (USBR, 2017)
Figure 2.3 Typical mixture proportions for conventional concrete (PCA, 2018)
11
16
6
26
41
Conventional concrete Cementitiousmaterial, 11%
Water, 16%
Air, 6%
Fine aggregate, 26%
Coarse aggregate,41%
12
Figure 2.4 Typical mixture proportions for RCC (PCA, 2018)
As can be seen in Figure 2.4, the RCC has a low proportion of air voids, which means that air-entraining admixtures are required to increase the air voids and thereby obtain a frost resistant concrete. When the air voids are developed artificially, they are not filled with water and therefore remain filled with air. Ice can form in these empty voids without applying pressure on the pore walls and by that capillary saturation can be achieved without exceeding the critical limit. (Rosenqvist, 2016)
In Table 2.4, some examples are shown of RCC mixture proportions from different dam projects that have been constructed over the years. All the quantities for each component are given.
Table 2.4 Examples of mixture proportions of RCC dams (ACI, 2011)
Dam Water [kg/m3]
Cement,[kg/m3]
Pozzolan, [kg/m3]
w/c Fine aggregate,
[kg/m3]
Coarse aggregate,
[kg/m3]
Air-entrained
admixture, [cm3/m3]
Air [%]
Water-reducing
admixture [cm3/m3]
Al Wehdah
25 70 60 0.4 910 1365 13 2 -
Camp Dyer
90 82 82 1.1 750 1344 4 3.6 2
Santa Cruz
101 76 75 1.3 728 1365 4 2.3 2
Upper Stillwater
94 79 173 1.2 729 1292 - 1.5 7
Willow Creek
110 104 47 1.1 645 1625 - 1.2 -
10
13
1.5
35
40.5
Roller compacted concrete
Cementitious material,10%
Water, 13%
Air, 1.5%
Fine aggregate, 35%
Coarse aggregate,40.5%
13
The water-cement ratio law, which is exemplified in Table 2.4, is generally used for fully consolidated mixtures, where the compressive strength of RCC is a function of the water-cementitious material ratio for mixtures that are fully compacted. This general relationship is represented in Figure 2.5.
Figure 2.5 General relationship between the compressive strength and the w/c (ACI, 2011)
For mixtures with dry consistency, where the voids are not fully filled with paste, the compressive strength is determined by the moisture-density relationship.
In general, poorly compacted mixtures consist of less-than-optimum moisture, which leads to a loss in strength and density. This can be counteracted by adding water to the mixture and thereby increasing the paste volume to fill the voids. A mixture that is fully consolidated and exceeds the optimum moisture usually creates a higher compressive strength. The tensile and shear strength, along the lift surfaces, typically determines the design strength while the compressive strength is more of an indicator of the quality of the concrete. (ACI, 2011)
2.2.2.2 Classification of RCC mixtures
The RCC mixture may vary when it comes to the amount of cement and this leads to the classification of RCC mixtures according to Table 2.5.
Table 2.5 Classification of RCC mixture (Chryso, 2018)
Classification Cement [kg/m3]
Lean paste RCC <100
Medium paste RCC 100-150
High paste RCC >150
14
The lean paste RCC is a mixture containing low amounts of cementitious material and these mixes are drier in consistency, leading to a less workable mixture with a Vebe time (See 2.2.2.3, Figure 2.6) less than 30 seconds. The minimized use of the cement or/and pozzolan leads to cost saving. An advantage with lean mixtures is that the concrete, which is created,has low internal temperature during the hydration and low elastic modulus but the concrete tend to have high creep rates which are important to consider.
For a lean mixture, compared to a high paste mixture, the quality of the bond is reduced between the lifts of the RCC is reduced. Lean mixtures provide adequate strength for sliding stability, but seepage is expected and measures needs to be taken to control it and this is described in section 3.2 After construction.
When constructing with high paste RCC the goal is that it performs just as well as a conventional concrete dam. This type of mixture contains a greater amount of pozzolan and cement, more than 150 kg/m3, to be able to obtain a density near the theoretical air-free density. (Hansen K.D et al.,1991)
2.2.2.3 Considerations
Workability
The workability is a way of determining the RCC capacity to be situated and compacted without damaging segregation. The definition of segregation is the separation of the concrete ingredients from each other and thereby resulting in a non-uniform mix. It is affected by cement, water, fly ash and fine aggregates. To check if the mixture is workable, a Vebe apparatus is typically used to measure the mixture consistency. (USACE, 2000)
The Vebe apparatus is connected to a vibrating table and filled with fresh concrete, which is compacted into a conical mould, see Figure 2.6. The mould is then removed and a clear plastic disc is placed on the top of the concrete. The vibrating table is started and the time it takes for the whole disc to fully come in contact with the concrete is the Vebe time.
Figure 2.6 Vebe apparatus (The Concrete Society, 2018)
15
The Vebe time, which is achieved for the RCC mixture, is used very similarly to the slump test for conventional concrete mixtures. According to SS-EN 12350-3:2009, to obtain an adequate workability, a Vebe consistency of 5-30 seconds is desired which will contribute to a uniform density through the whole lift, good bonding between the lifts, support of compaction equipment and easy compaction.
Durability
The durability of RCC will depend on the quality of the materials that are used, the exposureconditions and the expected performance level of the structure. Freezing-thawing and erosion caused by e.g. aggressive waters are processes that affect the durability and can be avoided by protecting the external sides, exposed to water, with conventional concrete. This can be done on both the upstream- and downstream face, all depending on if the faces are exposed ofdeterioration due to water or chemicals. (USACE, 2000)
Segregation
In order to reduce the risk of segregation of RCC during placing, spreading and transporting, it is of great importance to produce a cohesive mixture. Segregated material lead to a loss of properties of the RCC and this occurs in low-cementitious content mixtures due to its grainy consistency. By adding fine aggregates and controlling the moisture content this can be prevented. Mixtures with high paste-content are generally less likely to segregate due to being more cohesive. (ACI, 2011)
Heat generation
The heat generation during hydration of cementitious materials needs to be considered when designing massive RCC structures. Figure 2.7 shows an example of how the hydration heat of cement governs the rise of the temperature. The goal is to minimize the heat that is developed during the hydration to avoid the risk of thermal cracking but at the same time achieve sufficient strength growth by creating a suitable combination of pozzolan and cement. To achieve the optimal combination, tests on different percentages of pozzolan and cement mixtures are typically conducted. (ACI, 2011)
Figure 2.7 An example of adiabatic temperature rise due to hydration heat (Amberg, 2003)
16
Construction-conditions
The use of equipment and the requirements for construction is important to consider, due to the possibility of damaging the compacted RCC when it is placed. When rollers and hauling trucks are exposed to a RCC mixture with high workability it tends to leave wheel-tracks, which is also known as rut. For that reason, there should be a restriction from operating on a compacted surface until it reaches final set. (ACI, 2011)
2.2.2.4 Proportioning approaches
Two different proportioning techniques may be used when designing a new RCC dam and two main approaches has been developed. The first approach is the concrete approach and it is appropriate for high paste RCC mixtures, while the second approach is the soil approach and it suits RCC mixtures that are lean. These approaches are further explained below.
In the concrete approach RCC is considered to be a true concrete and that it is composed by clean and well-graded aggregates. When the RCC mixture is fully consolidated, the strength will be inversely proportional to its water-cement ratio. The consistency of the mixture using this approach is usually more viscous and the concept of having an adequate amount of paste to fill all the voids in the aggregate is applied. This is because fully compaction needs to be achieved with a no-slump consistency. However, it is important that a measurable slump doesnot appear which could occur if the mixture contains more paste than necessary. According to ICOLD (2003), the concrete approach is used in several methods that all has minordifferences but still follow the general process described in the following steps:
1. Increase the coarse and fine aggregates gradation to achieve minimum voids in the mixture.
2. Fill the voids in the fine aggregate with paste by choosing a suitable paste/mortar ratio. The material used should pass 75 μm sieve to be acceptable.
3. Adjust the proportion of the concrete components (cement, water, fly ash and admixtures) to obtain the appropriate mean strength.
4. Use the Vebe apparatus to achieve coarse aggregate volume that will lead to an acceptable workability.
5. Investigate if there is enough cementitious material and added fines to obtain the desired permeability.
6. Investigate that the fine/coarse aggregate ratio is as optimized as possible by comparing it to gradation curves.
7. Investigate that the generated heat during hydration does not exceed the expected limits.
8. Make any modifications that are needed and re-check the design.
The soil approach is based on the moisture-density relationship. Compared to the concrete approach, the RCC is considered as a processed soil which is enriched with cement. To find optimum moisture content for a specific amount of cement and aggregates, the mixture has to be able to carry a compaction effort corresponding to the vibratory rollers. Thereby a
17
maximum dry density can be obtained. It is common that all the voids in the aggregate are not filled with paste after compaction when using the soil approach. (USBR, 2017) When using the soil compaction method, the following steps are usually used (Harrington D et al., 2010):
1. Select well-graded aggregates
2. Choose a mid-range cementitious content
3. Develop plots of the moisture density relationship and verify that the moisture ratio is acceptable
4. Cast samples to measure the compressive strength
5. Test the specimens and choose required cementitious content
6. Calculate the mixture proportions
For conventional concrete, the mix design is similar to the RCC procedure based on the concrete approach, where the strength and water-cement ratio are the main aspects. The difference when testing the consistency of the conventional concrete is that slump is allowed.Some examples of slump values, suitable for different kinds of concrete, are presented in Table 2.6. (ACI, 2017)
Table 2.6 Recommended slumps for different types of concrete applications, according to ACI (2017)
Conventional concrete constructions
Slump [mm]
Maximum Minimum
Reinforced foundation and walls and footings
75 25
Plain footings, caissons and substructure walls
75 25
Beams and reinforced walls 100 25
Building columns 100 25
Pavements and slabs 75 25
Mass concrete 75 25
18
2.2.3 Properties of hardened concrete
2.2.3.1 Durability
Concrete and RCC dams are in general exposed to deterioration effects from abrasion/erosion, freezing/thawing and chemical attacks, which lead to degradation of the concrete. The interior of RCC can experience internal frost damage, due to ice-crystallization in the pore system. However, this can generally be counteracted with the help of air-entraining admixtures, which create larger volume of air voids for the water to spread out on. An alternative could be to have a higher quality concrete on the exterior than the interior concrete to avoid cracking, spalling and loss of material from the surface, thereby achieving a high durability.
Abrasion/erosion damage may occur in RCC dams because it is subjected to factors such as ice and waterborne sediments, see Figure 2.8. The quality of aggregates and the compressive strength determines the RCC’s resistance against abrasion/erosion. (ACI, 2011)
Figure 2.8 A spillway that has been subjected to hydro-abrasion (Eriksson D, 2018)
Generally, RCC has a poor resistance to freezing/thawing but by using conventional concrete or air-entrained admixture the risk of frost damages can be reduced (USBR, 2017). Figure 2.9shows typical frost damages that can appear on hydraulic structures.
Figure 2.9 Frost damage in a hydraulic structure (Eriksson D, 2018)
19
2.2.3.2 Strength
Similarly to conventional concrete, the mixture proportions of the components and the degree of compaction influence the strength of the RCC. The voids between aggregates in the mixture can be completely filled with paste or not, depending on the classification the mixture according to Table 2.5, and this determines the basic strength relationship for the RCC. Table 2.7 gives a general view of the compressive and tensile strength for the different classification of RCC mixtures. (USACE, 2000)
The compressive strength is an indicator for the total strength of RCC and it increases with time. It is comparable to that of conventional concrete, generally ranging from 28 to 41 MPa. (Roller Compacted Concrete, 2013) During the design phase, tests of the compressive strength are performed on cores that are drilled out from the built structure. The cores compressive strengths are compared to the compressive strengths of cylindrical specimens of trial mixtures see Table 2.8. These specimens are prepared typically 7, 28, 90, 180 days, and 1 year to be able to follow the mixtures strength gain. The modulus of elasticity and Poisson’s ratio can also be determined with the help of these specimens. (ACI, 2011)
The factors that influence the compressive strength of the RCC are water/cementitious material content, aggregates and the degree of compaction. For fully compacted RCC, the reduction in water content leads to increase in compressive strength. Although, water content below the optimum will cause voids in the mixture and that gives a weaker compressive strength. To obtain a compressive strength that is equal to conventional concrete, high-quality aggregates have to be used. (USBR, 2017)
Table 2.7 Strength for RCC (ICOLD, 2003)
Lean paste RCC Medium paste RCC High paste RCC
Compressive strength [MPa]
Mean 11.6 15.2 20.7
Direct tensile strength [MPa]
Mean 0.35 - 1.35
20
Table 2.8 Comparison of compressive strength of RCC: construction control cylinders vs. cores (ACI, 2011)
Cor
e st
reng
th [M
Pa] St
reng
th
17 0 18 13 36
Age
, da
ys
730 0 90 365
365
Stre
ngth
9 14 14 14 34
Age
, da
ys 90 42 28 180
180
Cyl
inde
r stre
ngth
[MPa
]
365
days 16 - - 9 74
90 d
ays
9 11 21 - 18
28 d
ays
3 9 18 2 13
NM
SA
[mm
]
75 75 37.5 50 50
w/c
1.00
1.43
0.82
0.93
0.39
Pozz
olan
[k
g/m
3 ]
33 0 62 77 173
Cem
ent
[kg/
m3 ]
70 66 125
71 79
Dam
Elk
Cre
ek
Mid
dle
Fork
Stac
ey
Spill
way
Stag
ecoa
ch
Upp
er
Still
wat
er
21
The tensile strength is the main consideration for the loading design and, compared to the compressive strength, it is mainly governed by the bond of the aggregates. In a RCC structure, the lift joints are the weakest zones and, as for a conventional concrete structure, the tensile strength in these points is an important property. (USACE, 2000)
The most suitable way to test the tensile strength between the lifts is with a direct tensile strength test. The result from this type of test depends on the lift joints maturity, the preparation of joint surface etc. If the tensile strength of the parent (unjointed) RCC is of interest, then a splitting tensile strength test of horizontal cores is generally used. This test is, compared to the direct tensile strength test, easier to carry out and is not as sensitive to micro-cracking from drying and thereby gives more consistent results. The tensile strength in the RCC joints is always lower than in the parent (unjointed) concrete and therefore, the tensile strength in the lifts will determine the design. In Table 2.9, the tensile strength and percentage of bonded joint strength are represented from some projects. (USACE, 2000)
22
Table 2.9 Tensile strength of drilled cores of RCC dams (ACI, 2011)
Test
type
DT
DT
% b
onde
d jo
ins
95 90
Tens
ile
stre
ngth
[M
Pa]
0.9
1.6
Com
pres
sive
st
reng
th
[MPa
]
14 31.9
Age
, da
ys 90 5000
Join
t ty
pe NB P
NM
SA
[mm
]
50 50
w/c
0.63
0.35
Pozz
olan
[k
g/m
3 ]
121
195
Cem
ent
[kg/
m3 ]
74 89
Dam
Oliv
enha
in
Upp
er
Still
lwat
er
Notes: Joint type: NB = no bedding; B = bedding mortar or concrete; P = parent concrete. Test type: DT = direct tensile test; ST = splitting tensile test.
23
One of the most important properties of RCC is shear strength of lift joints, which is the sum of the cohesion and the internal friction for bonded, intact lift joints. It can generally, be described by using Coulomb’s equation, shown below. (USACE, 2000)= + tan (eq. 2-1)
Where:s = unit shear stressc = unit cohesionp = unit normal stress
= the angle of internal friction
Parent shear strength test and lift joint shear strength test are two types of test that are typically performed when determining the shear strength of the RCC and examples of values from different projects are shown in Table 2.10. The parent shear strength test can be developed from cylinder specimens made in the laboratory or from cores drilled from a finished RCC dam. The RCC shear strength is usually similar to those for conventional concrete. The cohesion in this test varies with the amount of cement, paste and age, while the friction angle is affected by the aggregate type. (USACE, 2000)
The other test that is performed is the lift joint shear strength and it generally determines the critical shear strength for design. Compared to the shear strength of conventional concrete dam, the RCC shear strength for lift joints can be lower. The cohesion varies, as in the previous test, with the amount of cement paste but also the preparation of the lift joint and the exposure. Conditions improving the cohesion, and thereby strengthen the bond between the lifts, can be done by placing the RCC lifts rapidly over a fresh joint surface, applying an additional bonding mixture concrete or bedding mortar between lifts or increasing the cement content of the mixture. (USACE, 2000)
24
Table 2.10 Examples of shear strength of drilled cores in RCC dams (ACI, 2011)
Res
idua
l sh
ear
,deg
40 42 44 40
Res
idua
l sh
ear
cohe
sion
[k
Pa]
552
207
69 69
Shea
r ,d
eg
67 55 69 56
Peak
co
hesi
on
[kPa
]
758
2068
1586
586
Cor
e co
mpr
ess
ive
stre
ngth
[M
Pa]
14 27 18 10
Age
, da
ys 415
120
365
345
Join
t typ
e
NB P B NB
NM
SA
[mm
]
75 50 50 63
w/c
1.09
0.37
0.80
1.50
Pozz
olan
[k
g/m
3 ]
51 173
66 0
Cem
ent
[kg/
m3 ]
51 79 67 74
Dam
Gal
esvi
lle
Upp
er
Still
wat
er
Vic
toria
Zint
el
Can
yon
Notes: Joint type: NB = no bedding; B = bedding mortar or concrete; P = parent concrete.
25
2.2.3.3 Permeability
Permeability of RCC can be controlled by the degree of compaction, placement method, mixture proportioning and the use of bedding mortar on the lift surfaces. Due to the construction method of RCC dams, seepage can occur between horizontal lifts and through vertical contraction joints or cracks which leads to a reduction in tensile and shear strength. (USACE, 2000)
The main concern for permeability in concrete dams is the seepage in lift joints. To produce watertightness, high cementitious content mixtures are needed to provide sufficient bond with a newly placed lift. Lower cementitious content mixture does usually not provide adequate watertightness and needs to be treated with bedding mortar between the lifts. According to ACI (2011), RCC mixtures containing a paste and fine aggregate volume of 18-22% will contribute generally to a sufficient level of impermeability, which is similar to conventionalconcrete.
2.2.3.4 Density
The definition of density is the mass per unit volume and the RCC density relies on the degree of compaction and the density of the aggregate. Many RCC mixtures have low water content and insufficient entrained air that leads to a slightly higher density compared to conventional concrete. The conventional concrete has a density of approximately 2400 kg/m3 and can vary, whereas the density for RCC can be 1-3% greater and land on a density of 2424-2472 kg/m3.(USACE, 2000)
2.2.3.5 Elastic properties
The modulus of elasticity and Poisson’s ratio are the elastic properties of RCC, as well as for conventional concrete, and they are affected by factors such as strength, age, paste volume and aggregate type. (ICOLD, 2003)
The modulus of elasticity is the ratio between the normal stress and the corresponding strain and is generally, for a given aggregate type, a function of strength. It is usually assumed that the modulus of elasticity in compression is the same as in tension. When designing dams, it is desirable to have a low modulus of elasticity to decrease the possibility of cracking at a particular stress level, but this leads to greater deformation. To determine an acceptable low modulus of elasticity is important and can be done with laboratory tests on specimens. The stresses and strains, obtained from the strength tests, are plotted and the ratio between stress and strain will give the proper modulus of elasticity.
The poisson’s ratio is the ratio between the transverse strain and the axial strain due to a uniformly distributed axial stress. Conventional concrete and RCC has generally similar values of Poisson’s ratio and it varies typically between 0.17-0.22. (ACI, 2011)
Table 2.11 shows typical modulus of elasticity and Poisson’s ratio for some cases of RCC mixtures.
26
Table 2.11 Examples of elastic properties for different completed dams, according to ACI (2011)
Pois
sion
’s ra
tio
365
days -
0.21
0.14 - -
90 days -
0.19
0.14
0.18
0.21
26 days
0.17
0.14
0.13
0.19 -
7 da
ys -
0.13 - - -
Mod
ulus
of e
last
icity
[GPa
] 365
days
22.8
2
22.3
4
11.7
9
-
17.7
2
90 days
13.1
7
15.5
8
9.10
19.1
7
14.8
2
26 days
7.58
12.4
1
7.10
18.4
1
10.6
2
7 da
ys -
9.38 -
15.1
7
4.69
Com
pres
sive
Stre
ngth
[MPa
] 365
days
11.7
21.0
36.0
26.1
10.7
90 days
8.6
15.0
24.2
18.3
7.5
26 days
6.8
8.9
14.7
12.7
4.3
7 da
ys
4.4
4.4
9.4
6.9 19
w/c
1.03
0.88
0.47
1.06 2.0
NM
SA
[mm
]
75 50 50 75 75
Dam
Con
cep
cion
Sant
a C
ruz
Upp
er
Still
wat
er
Will
ow
Cre
ek
Zint
el
Cna
yon
27
2.2.3.6 Creep
Creep is a time-dependent deformation and under sustained long term loading, the creep will continue at a decreasing rate and increase in strain. High modulus of elasticity and high strength in the RCC will cause low creep, while low strength and modulus of elasticity leads to larger creep values. The desired creep values are typically high to gradually relieve stress and strain development caused by foundation restraint and exterior and thermal loading.According to Eurocode 2, the creep can be represented by the formula:( , ) = ( , ) (eq 2-2)
where,
= creep deformation( , ) = final value of creep coefficient = compressive strength, MPa= static modulus of elasticity, GPa= time after loading, days
The first part of the above equation represents the long-term effect of creep after loading,while the second part represents initial elastic strain from the load. Some examples of creep properties are given in Table 2.12.
28
Table 2.12 Strain and creep properties of some laboratory RCC mixtures, according to ACI (2011)
Mod
ulus
of
el
astic
ity
[GPa
]
- 10 14 10 12 13 8 11 13
Com
pres
sive
st
reng
th
[MPa
]
4 7 9 14 29 35 3 8 12
Cre
ep c
oeff
icie
nts
f(K
)
0.12
0.08
0.03
0.04
0.01
0.02
0.20
0.11 -
[10-
6 /KPa
]
0.20
0.11
0.07
0.10
0.08
0.08
0.29
0.16
0.08
Load
ing
age,
day
s
7 28 90 28 180
365 7 28 90
w/c
1.20
1.20
1.20
0.43
0.43
0.43
1.61
1.61
1.61
Pozz
olan
[k
g/m
3 ]
0 0 0 170
170
170
19 19 19
Cem
ent
[kg/
m3 ]
90 90 90 77 77 77 47 47 47
Dam
Con
cepc
ion
Upp
er
Still
wat
er
Will
ow C
reek
29
2.2.3.7 Volume change – shrinkage
It is important, for all massive concrete structures, to minimize uncontrolled cracking due to volume changes. These volume changes are divided into different types such as, dryingshrinkage, autogenous shrinkage and thermal contraction.
Drying shrinkage is defined as the volume reduction that the concrete exhibit due to the moisture migration when it is exposed to lower relative humidity environment. It depends onthe water content and the features of the aggregate that are used. Due to the lower water content in RCC, the drying shrinkage is either similar or lower than for conventional concrete. Compared to autogenous shrinkage, drying shrinkage takes place over a longer period of time. (USACE, 2000)
Autogenous shrinkage is the deformation that occurs during constant temperature with no exchange of moisture with its environment. The chemical shrinkage is the driving force and when hydration develops a volume change in the interior of the concrete occurs, without losing or gaining moisture in the concrete. Autogenous shrinkage is dependent on the properties of the used materials and the mixture proportions. Generally, higher strengthproperties may lead to higher autogenous shrinkage. (Barcelo L et al., 2005)
The thermal contraction takes place when the hydration process causes the concrete to reach temperature higher than the ambient temperature. When the hot concrete starts to cool down to the surrounding temperature, it contracts and reduces in volume. (BASF, 2014)
2.2.3.8 Thermal properties
The thermal properties, which include specific heat, coefficient of thermal expansion, conductivity and adiabatic temperature rise, are of great importance for both RCC and conventional concrete. In Table 2.13, examples of thermal properties for various projects are presented. It is recommended to test the mixture because the thermal properties vary significantly depending on aggregate and cementitious type and content. (ACI, 2011)
The adiabatic temperature change depends on the total cementitious content and percentage of pozzolan in the mixture. Compared to conventional concrete, RCC with low cementitious material content has lower temperature rise (ICOLD, 2003).
30
Table 2.13 Thermal properties of some laboratory RCC mixtures, according ACI (2011)
Adi
abat
ic te
mpe
ratu
re ri
se
Cha
nge
in C
28 days
13.9
11.1
18.3
26.7
12.2
7 da
ys
13.3
8.9
16.1
20.2 0
3 da
ys
11.7
7.2
13.9
13.3
7.2
Initi
al C
19.4
6.7
16.1
12.2
11.7
Coe
ffic
ient
of
ex
pans
ion
[mill
iont
hs/
C] 11 7 5.4 - 7
Con
duct
ivit
y [W
/m K
]
1.9
1.7
2.9 - 1.8
Diff
usiv
ity
[m2 /h
]
0.00
3
0.00
3
0.00
4
-
0.00
3
Spec
ific
heat
[J
/kg
C]
1047
754
1089 - 921
Agg
rega
te
type
Igni
mbr
ite
Sand
stone
Allu
vial
gr
anite
Qua
rts
Bas
alt
Pozz
olan
[k
g/m
3 ]
0 23 66 204
19
Cem
ent
[kg/
m3 ]
90 56 66 93 47
Dam
Con
cepc
ion
Elk
Cre
ek
Sata
Cru
z
Upp
er
Still
wat
er
Will
ow
Cre
ek
31
2.2.3.9 Tensile strain capacity
Cracks occur when a restrained volume change causes strain which exceeds the tensile strain capacity. There are several factors that affect the tensile strain capacity such as rate of loading, cementitious content, type of aggregate, age and strength of the concrete and aggregate shape (natural round vs. angular, which is produced by crushing). Development of tensile strains in the concrete occurs due to volume changes and external loads applied to the structure. (ACI, 2011)
32
2.3 Construction
2.3.1 Foundation considerations
For RCC dams, the foundation considerations are the same as for the conventional concrete dams. When designing, several aspects must be taken into consideration such as the loads from the dam and the stresses that are distributed on the foundation, the suitableness of the rock foundation, and the required quantity of surface treatment and excavation to achieve a suitable foundation.
The friction angle of the joint surfaces, the orientation and dip angles of key joint sets and the loads that are transmitted to the foundation must be taken into account when evaluating the foundation stability. Cohesion between the foundation and the dam is important to control sliding resistance of the contact surface. (USBR, 2017)
Conventional concrete is generally used to build a platform between the foundation and the RCC dam because this is the most critical point of the structure. After this, the RCC is placed in layers on a leveled surface. However, there are projects that directly have started with RCC on the foundation.
The goal when designing a new RCC dams is to reduce the amount of leveling concrete due to the use of conventional concrete is generally more expensive than RCC and it may have different properties. To avoid the use of leveling concrete, a thin layer of high-slump bedding concrete can be placed onto the rock and then spread over the RCC and compact it while the bedding concrete is fresh. This way the two materials merge into one after compaction and the mortar and grout of the bedding concrete creates sufficient bond. (ACI, 2011)
2.3.2 Construction method
When designing a new RCC dam it is important to consider the basic purpose of the dam and assure that the set requirements, e.g. cost, watertightness, appearance etc, are fulfilled. These aspects will determine for instance the mixture proportions of the RCC and the shape of the dam.
Aggregates that are used for RCC mixtures can be found on the construction site or it can be transported from an aggregate producer. Stockpiling aggregates is necessary for an RCC dam construction and before starting the RCC work. Huge stockpiles are needed because the aggregate production capability might be exceeded by the usage rate of the aggregate during the placement of the RCC. (ICOLD, 2003)
When producing aggregates it is critical to stockpile it cold or warm, depending on the time of the year that the production is done. There is a specified maximum temperature for the aggregates during placement and if warm weather is anticipated, then pre-cooling of the aggregates may be required which can be done by sprinkling water on the stockpiles to create evaporative cooling. It is however, important to consider the moisture of the aggregates when it is time to mix the RCC mixture. In general, if low placement temperatures are desired then stockpiling during the winter is the best option. (USBR, 2017)
33
The most crucial part of construction is that the RCC is transported, placed, spread and compacted as rapidly as possible. The time from the start of mixing to after it has been compacted should not exceed the initial set time of the RCC mixture. For mixtures containing no or little pozzolan the placing, spreading, and compacting should be executed within 30-45minutes of mixing and this general rule is suitable for mixtures containing retarding admixtures. However, this time can be adjusted depending on the weather conditions. For warmer weather the time should be reduced, while for cooler weather the time can be extended. (ICOLD, 2003)
Compared to when constructing a conventional concrete dam, RCC dam differs in the aspects of the layout, planning and equipment. Rather than building in blocks the RCC dam are usually built in thin, horizontal lifts which are advanced from one abutment to the other. When constructing RCC dams, the demand for man-hours are less compared to conventional concrete due to the usage of machines for compacting and spreading the concrete (see Figure 2.10), reduced amount of formwork and decreased joint preparation. RCC dams can be built with curved or straight axes, with inclined or vertical upstream face and with a downstream face with a vertical or an inclined slope depending on what is suitable for the given site. With time there has been a development of placing methods and the goal has been to place multiple RCC lifts in a short amount of time, before the initial set of the concrete is reached. This leads to an improved bond between each lift and the need for placing bonding mortar can be avoided.
Figure 2.10 RCC compaction (Shaw, 2010)
The sloped layer placing method (SLM) is one of the newer methods, where 10 small-volume lifts are rapidly placed on slopes from 1:10 to 1:40 that are later built up to a single layer which may have a thickness up to 3 m, see Figure 2.11. (ACI, 2011)
34
Figure 2.11 Sloped layer placing method, according to ACI (2011)
Bulldozers are the general equipment that is used for spreading RCC and it is typically placed in a 300-350 mm thick layers. An uncompacted lift gives the dozers the ability to work on the surface without damaging it. When it comes to the thickness after compaction, the most common lift thickness is 300 mm because it is suitable to work with in the field but it can be up to 500 mm thick. Factors such as maximum approved exposure time of a lift before placing the following one, affect the selection of the RCC layer thickness. Another factor is to use the maximum allowable lift thickness of a RCC mixture and to obtain the specified minimum density after spreading and compaction. For minimum potential weaknesses in the dam, thicker lifts are chosen which leads to longer exposure times but fewer joints between the lifts. If instead improved bond is required, then thinner lifts are chosen which consequently means more joints but these can be covered a lot sooner. It has to be taken into consideration that each project is unique and different lift thicknesses may be optimal.(ICOLD,2003)
Upholding the bond between lifts is important for both RCC and conventional concrete dams in order to fulfill the necessary factors of safety for usual, unusual and extreme loading conditions. The following requirements are essential to obtain an adequate bonding between the lifts (USBR, 2017):
1. Having a RCC mixture with adequate workability and sufficient amount of paste andmortar.
2. To control segregation when placing the RCC.
3. Achieving an adequate compaction with the vibrating roller.
4. Thorough cleanup of the lift surfaces.
5. Using a bonding layer of concrete or mortar between lifts.
6. Placing RCC rapidly and thereby reducing the exposure time of the lifts.
35
As mentioned earlier, the bond between the lifts are important especially for hydraulic structures. The quality of the bond relies on the type of joint treatment that is required. The joint treatment is dependent on the time between placements of the lifts and the time relies upon the RCC mixture and the surrounding temperature at the site. There are three types of joints, which are explained further. (USBR, 2017)
Hot joint (fresh joint) appears when placing a new RCC lift over the earlier placed lift that has not reached its initial set (between 6-12 hours from placement). The common cleanup treatment (Type 1) includes the removal of loose materials and free water and then cleaning the lift surface with vacuum equipment. If the mixture contains no pozzolan or if the placing occurs during warm temperature conditions, then the time period 6-12 hours is reduced down to 4 hours.Cold joint appears between the initial and final set (6-24 hours after placement). The cleanup treatment (Type 2) includes cleaning with air- or air water jetting to remove concrete that is defected then vacuuming the surface to remove remaining loose materials or water. Depending on the design conditions bonding mortar may be needed.Construction joint appears after the final set of the concrete (24-48 hours after placement). The cleanup treatment (Type 3) is important and it includes high-pressure water jetting or wet sand blasting to remove loose materials and water, then a mechanical broom and vacuum is followed. Bonding mortar is commonly needed.
To control cracking caused by thermal volume change, contraction joints are used and is an important part of the design. Contraction joints formed by a crack inducing plate is done by firstly spreading the RCC to the contraction joint alignment and then prepare a vertical form plate for the joint with some external support to keep the plate vertical. On both sides of the vertical plate, RCC is spread with manual labor. It is common to use plastic sheets around the vertical plate which is later on removed, leaving the plastic to act as a bond breaker. See Figure 2.12. Another method to create a contraction joint is with a vertical plate attached to anexcavating machine called backhoe, which has a bucket attached to its arm. The galvanized steel plate is installed by vibrating it into the compacted lifts into pre-made joint location and these acts like bond breakers due to they are left in the RCC. The joints placing and spacing is determined by the temperature change and the time period it develops, the foundation restraints, the creep relaxation, the tensile strain capacity of the concrete, the applied loads and the coefficient of thermal expansion (USBR, 2017). According to Cotoi (2015), a general rule could be to place the contraction joints every 15 m throughout the dam.
36
Figure 2.12 Induced joints placed with RCC placement (Shaw, 2010)
37
The construction of contraction joints can vary from a superficial crack and control of seepage, to detailed joints with drain holes, tubes for grouting and water stops. If the contraction joint consists of the superficial crack and seepage control construction, then a wood strip of 40x45 mm is installed as a crack inducer and treated or sealed with a joint sealer and a foam. A contraction joint that consists of a water stop and a drain, commonly places the water stop in conventional concrete at a certain distance from the dams upstream face and joint filler is placed on both downstream and upstream of the water stop. Contraction joints with drain holes are formed during the time when the RCC is placed and the drain hole is connected to the drainage gallery through an outlet pipe. (ACI, 2011)
Galleries are important to have in dams over 30 m in height in order to create places that are used for inspection and observing the behavior of the dam, drilling drain and grout holes into the foundation and seepage draining. It is important to place the galleries so that they do not interfere with the construction of the dam. There are many construction methods for designing galleries e.g. conventional forming method with or without the use of conventional concrete or excavation of gravel in-fill from the gallery area. (ACI, 2017)
The design of spillways that is used for conventional concrete dams is applicable for RCC dams. There are four kinds of spillways, when overtopping is desired, for RCC dams and they are: naturally sloped RCC spillways, stepped RCC spillways, stepped conventional concrete spillways and sloped conventional concrete spillways. It is common to use conventional concrete steps for the spillways when constructing RCC dams and it can be constructed either after the RCC is complete, similar to how it is done to most smooth spillway facings, or it can be done lift by lift with the RCC. If the spillway is not strengthened with conventional concrete, then the RCC can be used if the water flow velocity is less than 8 m/sec. (USACE, 2000)
When the RCC has been placed and compacted, continuous curing is important just as for conventional concrete. The RCC is a drier mixture and the surface tends to dry faster during warm weather. Therefore, it should be maintained in a moist condition with water for 14 days or until the next lift is placed. The RCC must be protected from extreme temperature changes until it gains adequate strength and the construction should cease if the rain exceeds 2-3mm/h. If vehicles are allowed on the surface during rain, the tires may damage the surface and turn the material soft. This situation may need waiting until the RCC has hardened and cleanup can be done or removal of the entire lift is done. (USBR, 2017)
38
39
3 Challenges during construction
3.1 During construction
The main reasons for designing new RCC dams are the economy, the speed of constructing it and the positive environmental affect due to less cement use. As for every other type of dam, the RCC dam may face challenges during construction. There are typical conditions which need to be taken into consideration, and those are topography, foundation, geology, access conditions, climate conditions, available materials and characteristics of the river flow. The handling of these conditions can be found from earlier experience from previous projects. However, there is no standard solution when designing a RCC dam, or any other type of dam, due to characteristics of the specific site, which makes every project unique in design. (Griggs T et al., 2012)
Nowadays, RCC dams are being constructed in all types of climate all over the world. This means that the circumstances for construction can be exposed to extreme cold or warm climate conditions, which both can lead to cracking in the structure. During construction, when the placing of the lifts takes place, the initial hydration can affect the maximum temperature to increase or decrease depending on the ambient condition and exposure time.The major concerns when cracking in the RCC occurs are leakage control, durability and appearance. The most difficult factor to control after construction is the leakage and often results in an unwanted loss of water and is problematic to maintain. (ACI, 2011)
When constructing a RCC dam in cold climate, it is important to consider possible difficulties due to rapid cooling of the massive RCC construction and how this could be handled can be seen in the project of Xingjiang Shimenzi Reservoir. The region has temperatures below zero around 1/3 of the year and temperature can reach -36°C, making this a very harsh climate to build in. Important measures were taken, where the first step was to create a mixture with good freezing and thawing resistance with the help of air-entraining admixture. When the RCC mixture was transported to site it was insulated and the placement area was fully insulated with insulating layers. Actions were taken to protect the existing RCC against frost by using weaving cloth, gravel and grass cushions to enclose the surface of the RCC during the time when there was low activity in the construction phase. (Berga L et al., 2003)
Constructing in warm climate can be challenging as well. When placing the RCC lifts in warm conditions, the surface will absorb the direct heat from the sun which will cause an increase of the mixtures temperature and it will generate the hydration more rapidly. If the surface of the lift is exposed during a long time, it will have the chance of absorbing so much solar energy that it will force the internal temperature to increase. (ACI, 2011) That is why rapid placement is suitable in this case and an example of a dam that was built during warm conditions is the Al Wehdah dam on the border between Jordan and Syria. This project started May 2003 and during the summer months the temperature could reach up to 40 C. This was taken into account by incorporating chilled water into the mixture and thereby reducing the placement temperature of the RCC. Also, the coarse aggregates were kept chilled with the help of a moving wet belt system, which in other words is a cooling tunnel and it used water that was chilled down to 3 C. (Water Power, 2009)
40
3.2 After construction
The design and construction develops with time and each completed project and this provides experience and knowledge, which can be used in future RCC dam designing. Therefore, it is important to achieve reports or records with accurate results of the performance and to learn from earlier mistakes that has lead to unsatisfactory performance. After the construction is completed core samples are drilled out and they often contain the joints between the lifts which can be examined and tested for strength.
A new RCC dam will experience thermal stresses that are directly related to volume changes of the concrete, due to the hydration process and the ambient temperature variations leading to cracks. The dam may be exposed to temperature differences up to 60-70 C, within a summer to winter period, resulting in opening and closing of cracks and joints in the RCC dam. (USBR, 2017) These temperature variations are commonly considered when designing the dam and can be anticipated with the help of FE- analysis. An example of the temperature distribution is shown in Figure 3.1.
Figure 3.1 Example of temperature distribution in a concrete dam according to USBR (2006).
Cracking can be expected in any type of concrete dam and develops because of tensile strain, caused by the cooling of the concrete from the peak temperature. A common thing to do to prevent cracks, is to install crack or joint inducers in the bigger dam constructions to help control the cracking and they are placed every 15 m, see Section 2.3.2, with drain holes and upstream water stops. The cracks that are of concern, when the dam is in use, are the ones that are below the waterline and are wide enough to let water pass through. These cracks can be repaired or sealed with different method and materials and one way is to use a sealant consisting of polysulfide and polyurethane or cement grouting. The repairing could be done when the water reservoir is lowered or underwater crack sealing can be implemented with e.g. quick-set cement. (ACI, 2011)
Seepage can be one of the most challenging parts after construction. If it is not handled properly, it can lead to internal failure modes where the lifts will slide, see Figure 3.2, due to water flowing through the cracks causing a hydrostatic pressure. Due to the water, leaching of the concrete will occur, which will increase the deterioration.
41
Figure 3.2 Internal failure modes due to seepage.
Seepage can consist of leakage through cracks and joints, seepage through the RCC material itself and seepage through the foundation materials. The characteristics of the voids in the mixture, which can develop due to segregation of large aggregate near the bottom of the lift, is what determines if the water has a chance to pass through the RCC. However, this can be counteracted in the mixture stage where higher cementitious contents, higher fines content and the construction method can be adapted. During construction, it is important to put weight on installing water stops and applying sealants at the joints because this minimizes the seepage through the dam. The permeability of the placed RCC can then be controlled by water-pressure testing in vertical drilled holes in the dam’s body. Leakage is defined as the water that passes through cracks and joints in the structure and is usually easier to repair than seepage through the entire RCC dam. (ACI, 2011)
The RCC material on existing dams has proven to have high erosion resistance due to a high aggregate content, both coarse and fine. The RCC resistance against erosion should be evaluated when high velocity and high volume flow over the surface is involved. An example of a dam which had all of the above mentioned factors was the Kerrville Ponding dam in Texas which had a total height of 6.4 m. The dam was overtopped with as much as 4.4 m at one point and the erosion was hardly noticeable except for some uncompacted material washed away on the downstream side. (Beene R.R.W et al., 1988) A problem that could develop due to overtopping, however, is erosion in the foundation. This can lead to losing the support of the foundation and thereby causing entire failure of the dam.
42
3.3 Construction of existing dams
3.3.1 Upper Stillwater
Upper Stillwater is an RCC dam in Utah, which began its construction in 1985 and was completed in 1987. The dam has a height of almost 90 m and a crest length of approximately 815 m and the dam itself needed 1 125 000 m3 of RCC to build it. The mixture that was used was a high paste RCC; see Table 2.4 for cementitious material content and 2.5 for classification of RCC, with a wet consistency. The downstream stepped face of the central spillway and the upstream vertical face were slip formed with conventional concrete and due to the use of a high paste RCC mix, a high tensile strength was achieved leading to a reduction of the cross-section of the dam. The high paste mixture and the conventional concrete facing on the upstream side also provided improved sealing and prevented seepage through the lift joints. (Abdo, 2008)
Upper Stillwater did not incorporate contraction joints and vertical thermal cracks did develop at a spacing of approximately 58 m. Most of the cracks were not significant in a structural point of view, however, one specific crack became critical and produced excessive leakage of water and necessary waterproofing repairs were made with the help of chemical grout and embedded steel barriers in the cracks. (USBR, 2006)
Figure 3.3 Upper Stillwater dam
43
3.3.2 Willow Creek
Willow Creek is an RCC dam in Oregon and it was constructed in 1982 and was originally planned to be built as a rock fill embankment dam. The dam was needed around 331 000 m3
of RCC and it was placed in less than five months, which proved that an RCC dam could be built faster than a comparable concrete gravity dam or an earthfill dam.
The dam used a lean paste RCC, see Table 2.12, and no transverse joints were included in the structure. The downstream face was unformed, while the upstream face used precast concrete panels. The biggest issues after construction with this dam was large leakage of water occurred and this was handled with the help of cement grouting. (Abdo, 2008)
Figure 3.4 Willow Creek dam
44
45
4 Design of new RCC dams
4.1 Design criteria
When designing a RCC dam the most influential considerations are the owner’s requirement for cost, time-schedule, appearance, water-tightness, method of construction and maintenance. The most common type that has been built up to date is the gravity RCC dam and therefore this type will be highlighted when designing in this chapter. There is no absolute difference between the design of a RCC gravity dam and a conventional concrete gravity dam and for that reason the same formulas and principles are used.
When designing dams in Sweden, RIDAS is used, which is the power producing company’s guideline for dam safety. It states requirements for durability, strength and stability of the dam as well as what criteria it needs to fulfill.
There are three essential criteria that must be fulfilled when designing RCC dams and they are(Hansen K.D et al., 1991):
1. No sliding – due to the layer construction method sliding can occur between the horizontal planes of the dam or at the connection between the foundation material and the dam, which needs to be avoided.
Figure 4.1 Sliding failure
2. No overturning – overturning must be prevented and it can take place at the connection with the foundation or in the foundation.
46
Figure 4.2 Overturning failure
3. Cross-section – the stresses that develop in the foundation or the concrete must notexceed the allowable stresses for the cross-section.
4.2 Loads
The RCC dam is typically subjected to horizontal and vertical loads and these are illustratedFigure 4.3.
Figure 4.3 Loads acting on the dam (Broberg L et al., 1991)
The loads that are acting on the dam are explained in Table 4.1
47
Table 4.1 Loads and their description (Hansen K.D, 1991)
Loads Description
P1, P2 Hydrostatic pressure on the upstream face of the reservoir.
P3, P4 Hydrostatic pressure of tail-water against the downstream face.
P5 Uplift pressure on any horizontal plane and internal hydrostatic pressure.
P6 Gravity dead load of the dam and additions such as bridges and gates.
P7 Ice load acting on the face of the dam.
P8 Silt pressure*.
P9, P10, P11 Seismic loads, horizontal and vertical accelerations caused by earth quakes*.
NOTE: The silt pressure (P8) is low in Sweden. The loads P9, P10 and P11are not considered in RIDAS.
4.3 Loading combinations
The design and analysis of dam stability should be performed by using safety factors for overturning and allowed friction coefficient for sliding, all according to RIDAS. For cross-section analyses, Eurocode 2 and partial coefficient method is used.
4.3.1 Load cases for calculation of stability
It is of great importance that the RCC dam is designed for all reasonable types of loading combinations with the loadings that are mentioned above and it can be categorized in to three combinations (Hansen K.D, 1991):
Normal load case
1. The water surface at the retention water level, maximum ice pressure and closed gates.
2. The water surface at the retention water level, temporary shutdowns, no ice pressureduring ice-free maintenance.
3. The water surface at the retention water level combined with closed gates in a spillwayand shut adjacent spillway, no ice pressure during ice-free maintenance.
4. The water surface at the retention water level and the most unfavorable combination ofopen and closed spillways and associated water level on the downstream side.
48
5. The water level at discharge of flows of flood design category II. For existing dams this load case may involve flooding.
Exceptional load case
1. The water surface at the concrete dams crest or to the lowest level of the top edge of the adjoining embankment dam, no ice pressure, the most unfavorable combination of open and closed spillways.
2. The surface of the water at discharge of the design flow. This only applies for dams in flood design category I. For existing dams this load case may lead to flooding.
3. If the drainage function cannot be controlled, the dams with drainage shall be checked with the load case with clogged drain, i.e. the dam is calculated for the same uplift pressure as a dam without drainage.
4. Asymmetrical ice pressure, such as one-sided pressure from spillway-pillar.
5. Load cases that may occur during the construction time.
Accidental load case
1. Exceptionally high water level due to a spillway is out of operation at the design flow. This load case is applied where a spillway for some reason are liable to fail, e.g. due to failing to open the gates.
2. Exceptionally high water level as a result of large amount of water drains down into a small water magazine.
3. Sabotage, explosion or other accidents that may cause extreme loads.
4.3.2 Load cases for cross-section analysis
There are limit states that are divided into three categories; serviceability limit state, ultimate limit state and accidents and each of these has load cases that can occur and be analyzed.(RIDAS, 2017)
Serviceability limit state
1. The water surface at the retention water level, maximum ice pressure and closed gates.
Ultimate limit state
2. The water surface up to the retention water level, maximum ice pressure (or load) and closed gates.
3. The water surface up to the concrete dam crest, no ice pressure, unfavorable combination of temporary shutdowns, open or closed spillways and he associated water at the downstream side.
49
4. If the drainage function cannot be controlled, the dams with drainage should be checked for the load case clogged drainage, i.e. the dam is calculated for the same uplift pressure as dams without drainage.
5. Asymmetrical ice pressure.
6. Load cases that may occur during the construction period.
Accidental load case
7. The same load cases as for the stability calculations.
4.4 Design of cross-section
The design of the cross-section of the dam should according to RIDAS be performed in accordance with Eurocode 2 and is based on the partial coefficient method, according to which design load values are obtained by multiplying characteristic values with partial coefficients. Design material values are obtained in a similar way by dividing characteristic material values with the partial coefficients which is shown in Section 4.4.2.
4.4.1 Load values and combinations
There are partial coefficients and for different dam safety classes which are shown in Table 4.1 and since both of them are to be used for unfavorable loads, the partial coefficient
is introduced. It should be taken into account that in some cases under the dam´s lifetime the dam safety class changes so the dam owner should consider increasing the safety class of at least one level when designing new constructions. When evaluating or changing an existing dam, the safety level of the current dam safety class can be used.
Table 4.2 Partial factors , and for different dam safety classes (RIDAS, 2017)
Dam safety class
A 1.1 1.2 1.3
B 1.0 1.2 1.2
C 0.91 1.2 1.1
RIDAS-class D and E 0.83 1.2 1.0
50
Table 4.3 Loading combinations for serviceability- and ultimate limit state (RIDAS, 2017)
Ultimate limit state Serviceability limit state
Combination of loads
6.10a 6.10b 6.14b 6.15b 6.16b
Permanent load (G)
Unfavorable 1,35 1,2 1,0 1,0 1,0 Favorable 1,0 1,0
Tension force (P)
Unfavorable 1,35 1,35 1,0 1,0 1,0 Favorable 1,0 1,0 1,0 1,0 1,0
Variable load (Q)
Leading load - 1,5 , 1,0 , , ,Other variable loads , , 1,5 , , 1,5 , , , , , , , ,
According to Table 4.3 above the variable loads has to be multiplied with a load reduction factor . The following Table 4.4 shows the load reduction factor for loads, that are relevant for dam constructions.
51
According to Eurocode 2, two load combinations in the ultimate limit state are specified:
, , + + , , , + , , , (6.10 ) , , + + , , + , , , (6.10 )
The first equation is used for design when the permanent load is the dominant one. Water load at the retention water level should be regarded as permanent load and water load above this level should be regarded as variable. There are also three loading combinations in the serviceability limit state are specified:
, + + , + , , (6.14 ) , + + , , + , , (6.15 ) , + + , , (6.16 )
The loading combinations in these limits states are presented in Table 4.3.
52
Table 4.4 Load reduction factor (RIDAS, 2017)
Load Load reduction factor
Variable water load 0.8 0.8 0
Wave loads 0.4 0.4 0
Stream pressure 0.4 0.4 0
Surging pressure 0.6 0 0
Wind load 0.3 0.2 0
Snow load 0.8 0.6 0.2
Ice load 0.8 0.6 0
Variable soil pressure 0.5 0.3 0
Temperature change 0.6 0.6 0.5
Moving-machine parts 0.8 vertical load
0.5 horizontal load
0.7 vertical load
0.5 horizontal load
0.6 vertical load
0 horizontal load
Traffic load 0.75 0.75 0
4.4.2 Material values
In the ultimate limit state the design values for concrete are calculated according to:
Compressive strength: = / (eq 3-1)
Tensile strength: = , / (eq 3-2)
Modulus of elasticity: = / (eq 3-3)
Where = 1.5 is the concrete partial material safety factor and = 1.2 is the partial safety factor for the modulus of elasticity of concrete.
53
4.5 Stability conditions
There are two types of safety factors which must be checked for the normal, exceptional, and accidental load case, one for sliding and one for overturning.
Loads will be calculated without partial coefficient, although in some cases additional estimations are implemented appropriately for calibration of coefficients. Control is performed for both individual and monolithic constructions. This ensures that the structure has sufficient stiffness and strength so that monolithic interaction prevails.
4.5.1 Safety against sliding, μ
Safety against sliding is controlled by making sure that the horizontal forces can be transmitted from the structure to the foundation.
In Sweden, cohesion in the intersection between the dam and the foundation is generally not considered when calculating the total sliding resistance.
Sliding control is performed for the abutment surface between the rock and the concrete as well as for possible weaknesses in the foundation. Moreover, sliding control must be done for weak points in the RCC dam structure itself, for example, the lift joints. The cohesive strength can vary and must be carefully selected when executing a sliding analysis. Lift joints that has been treated with bedding mortar can have an initial cohesion design of 5 percent of the compressive strength. Whereas, lift joint surfaces that has no bedding mortar the cohesion is assumed to be 0. The friction angle can be assumed to be 45 degrees when doing preliminary design studies, but it can vary between 40 to 60 degrees. To be able to verify if the assumed values are acceptable, testing is done on samples that are prepared in the laboratory and on drilled out cores from the design stage. The tests give an idea whether the shear resistance of the lift joint fulfills or exceeds the design requirements. (USACE, 2000)
The safety against sliding is satisfied if the current calculated sliding factor μ does not exceed the permitted value in parallel respectively perpendicular to the sliding plane.
According to RIDAS (2017), the value is obtained by dividing the ultimate capacity of the friction angle with a safety factor as shown in Table 4.5 below. The value of tan is determined based on the examined results.= = (eq 3-4) where, = Resulting forces parallel to the foundation = Resulting forces perpendicular to the foundation = Ultimate capacity for the coefficient of friction in the sliding surface
54
= Safety factor
Table 4.5 Safety factor for calculating (RIDAS, 2017)
Foundation Normal load case Exceptional load case Accidental load case
Rock 1.35 1.10 1.05
Moraine, gravel, sand 1.50 1.35 1.25
Silt 1.50 1.35 1.25
For rock foundation that has a good quality of moraine, gravel, sand and coarse silt, the values are used according to Table 4.6 below for checking the gliding safety in the section between the dam and the foundation.
Table 4.6 Allowed friction coefficient when the foundation consists of good rock or packed moraine, gravel, sand or silt. (RIDAS, 2017)
Foundation Normal load case Exceptional load case
Accidental load case
values at failure
Rock 0.75 0.90 0.95 1.00
Moraine, gravel, sand
0.50 0.55 0.60 0.75
Silt 0.40 0.45 0.50 0.60
The impact of a slope of the sliding plane can be considered by dividing action forces into components along the sliding plane and perpendicular to the plane. When checking the sliding plane, the allowable coefficient of friction is determined based on the examined foundation tests.
With a foundation based on friction materials, sliding stability must produce in the contact area between the dam structure and the foundation, but also along the lower weak layer under the dam structure.
55
4.5.2 Safety against overturning, s
The relationship between stabilizing and overturning moment must be higher than the given value for safety against overturning, see equation 3-5. Moreover, the resultant force at usual load combinations should be located within the core boundary. However, the requirement for resultant in the core boundary cannot be regarded as safe against overturning. Instead with the core boundary condition, the entire foundation area is compressed which causes a linear decrease of the distribution of the uplift pressure under the dam. It is particularly important for dams with a thin front plate to be pressed against the bottom of the dam otherwise leakage can appear at the weak parts of the foundation. For unusual load combination the resultant can appear outside the core area but within the “3/5” area. A part of the bottom area will not be compressed and fully developed uplift pressure is assumed over this area. For non-rectangular bottom shapes, the “3/5” area is undefined, but is suggested to be designed as follows:
Figure 4.4 For a continuous massive dam the “3/5”-area is the area in the middle of the three fifths.
56
Figure 4.5 If the same ratio is chosen between the core boundary and the “3/5”-area, the distance is moved outside the core area for a monolith with a rectangular bottom area.
Figure 4.6 For a monolith with irregular bottom area the core area is first calculated on the bottom area, which, with regard to stiffness, is included in the monolith. A base area is defined by the lines that surround the bottom area. The “3/5”-area is formed by increasing the limit of 40 % towards the nearest edge of the base area.
The position of the overturning axis is determined in the relation to the stiffness and strength of the concrete or the foundation. The overturning axis can normally be placed at the downstream edge of the dam for foundation placed on rock. When determining the overturning axis the strength and stiffness of the structure and the foundation must be considered.
57
The safety against overturning, , is calculated as the ratio between stabilizing and overturning moment: = (eq 3-5)
When relevant, the hydrostatic water pressure should be divided into overturning and stabilizing components e.g. for the sloping upstream side of the dam.
The safety factors against overturning are defined by RIDAS are presented in Table 4.7.
Table 4.7 Safety factors against overturning (RIDAS, 2017)
Type of load combinations Safety factor, s
Normal load case 1.5
Exceptional load case 1.35
Accidental load case 1.1
58
59
5 Case study
5.1 Background
Hylte hydropower plant, owned by Statkraft Sverige AB, is located approximately 4.5 kmnortheast of Halmstad in Hyltebruk and is one of the top hydropower plants in Nissan. Hylte consists of 18 dams, where the regulating dam is a concrete dam (Dam 17) and the remainingdams are embankment dams. The locations of the dams are shown in Figure 5.1.
Figure 5. 1 Overview of the dams included in Hylte power planet (SWECO, 2014)
The Hylte hydropower plant consists of dams that were built in the beginning of 1900s and the design requirements has gotten stricter since the dam was built. (Hylte, 2018). Therefore,the dams of Hylte power plant requires an increase in dam safety, and in order to satisfy the new design criteria’s, Statkraft intends to build a new regulating dam of concrete (dam 17) and new connecting embankment dams (dam 18 and partially dam 16), located 50 m downstream from the current regulating dam. The existing regulating dam (dam 17) and embankment dam 18 will be used as coffer dams during the construction of the new dams. When the new downstream control dam is taken into operation, the existing control dam and parts of the existing embankment dam 18 are demolished. (SWECO, 2014)
The purpose of this case study is to investigate whether a RCC dam could be built, and in such case what approximate dimensions would be required for it.
60
5.2 Calculation & CADAM
The tools that were used for this case study were hand calculations and the computer program CADAM, which is a tool used to analyze safety and structural behavior for massive concrete dams (Leclerc et al., 2001).
Hand calculations were made with the help of Chapter 4, where the main focus was on the stability analysis. Dimensions of the dam were determined by checking it for both overturning and sliding. No cross-section analysis was made.
CADAM was used to analyze sliding in the horizontal lift and to create the model of the dam with the achieved dimension from the hand calculations.
5.3 Results
The foundation, which the RCC dam is to be placed on, varies in height. It consists of rock,sandy soil and moraine and for that reason we have different limits for the safety factoragainst sliding that ranges from 0.50 to 0.75 for normal load case. To achieve a dam that issafe from overturning the safety factor must exceed the value of 1.5 according to RIDAS(2017). The water level varies due to the uneven topography between 3.9-8.2 m and that is why the height of the dam also varies, see Table 5.1.
The dam was divided into four sections; see Figure 5.2, due to the variation of the height ofthe topography. The geometry of the dam was governed by the roadways width. The width of the dam, placed on the rock, could have been less, and still fulfil the criteria’s in RIDAS. However, in this case study the slope 1:1.5 was chosen.
Figure 5.2 Hylte dam
61
Table 5.1 Results from hand calculations
Section Water level [m] Dam height [m] Safety factor against sliding
Safety factor against
overturning130 8.2 9.5 0.3 2.8
220 5.2 6.5 0.2 3.4
285 3.9 5.2 0.2 3.8
320 4.1 5.4 0.2 3.7
The results from CADAM is presented in Table 5.2 and 5.3.
Table 5.2 Global force and moments from CADAM, for section 130
Normal force -1521.828 kN
Shear force 379.812 kN
Uplift force 466.56 kN
Moment 42.731 kNm
Resultant position 50.266%
Table 5.3 Safety factors from CADAM, for section 130.
Peak sliding safety factor 3.0193
Residual sliding safety factor 3.0193
Overturning safety factor towards downstrem 2.789
Uplifting safety factor 4.262
As can be seen from Table 5.1, section 130, and Table 5.3, the overturning factor is the same for both hand calculation and CADAM.
For the sliding factor, in Table 5.3 the = 3.0193 that gives = = . = 0.33.
Compared to the sliding safety factor from the hand calculations presented in Table 5.1 for section 130, CADAM sliding safety factor is the same.
62
Figure 5.2 shows a cross section of the RCC dam for the maximum height of the dam.
Figure 5.3 Cross-section 130 of the dam, model from CADAM
63
6 Conclusions
6.1 Discussion
Building with roller compacted concrete (RCC) has become very popular over the past two decades. It has been used for both building new dams, improving existing conventional concrete dams that has been in need for repair and used as cofferdams. The most leading countries of constructing RCC dams are the United States and China.
The advantages of RCC are applicable for certain types of mixtures, production methods, structural design weather or among other conditions. Same goes for the disadvantages, which only applies for specific designs and site conditions. From a construction point of view, RCCis generally practical to build with and has four main advantages: high-speed construction, being cost-effective, good performance and smaller CO2 emissions than conventional concrete. (The Constructor, 2017) There are, however, situations when RCC may not besuitable and can become very costly compared to other types of dam. These factors could be e.g. poor quality of the rock foundation and not reasonably available aggregate material.
The RCC has the same basic ingredients as conventional concrete, where the main difference being the ratios of the input materials. RCC has a no-slump consistency, which is stiff enough to be compacted by a vibratory roller. The aggregates that are used in RCC may have the same standard as for conventional concrete, but it can also use aggregates that do not fulfill the normal standards. This makes RCC easier to create since the aggregates from site can be used.
When designing an RCC dam, the same standards are used as for conventional concretewhereas in Sweden, RIDAS is used. The same type of stability and cross-section analysis are applied, which means that the RCC dam has to fulfill the same type of criteria as a conventional concrete dam. See Chapter 4.
In Chapter 3, challenges for constructing the RCC were presented. It is of importance to understand that RCC dams are built all over the world, in all types of climates. This means that every project is unique when it comes to the challenges it meets. Weather conditions are one of the challenges the RCC dam building needs to handle, both during and after construction.
If an RCC dam were to be built in Sweden, the environment would be one of the main challenges. The dam would be exposed to temperature differences to up to 60-70 C, within asummer to winter period, making it move through thermal shrinkage and expansion. Another challenge with building an RCC dam in Sweden would be to give it adequate frost resistance. Due to the cold climate, the risk for frost deterioration is high in Sweden and it could lead to severe consequences to the functionality, safety and the durability of the dam since it diminishes the strength of the concrete.
64
The fly ash use in concrete in Sweden is not as common as in e.g. the United States. According to USACE (2000), generally up to 50 % by volume of fly ash can be used to replace cement in the RCC mixture. In Sweden, however, only 25 % or less by volume is allowed according to SS EN 206 in conventional concrete, indicating how fly ash is not as commonly used and it can therefore be a challenge to motivate to utilize larger quantities of it.
6.2 Future studies
Further studies can focus on the use of fly ash, because compared to international standards; fly ash is not as widely used in concrete in Sweden. Therefore, finding a motivation to use more fly ash, if RCC dams are to be built, could be reasonable.
Investigating how to improve the frost resistance could be another future study. Building dams in cold climates, such as in Sweden, frost will always be an upcoming problem and finding efficient ways to handle it is of great importance.
65
Bibliography
Abdo F (2008): Roller-Compacted concrete dams: Design and Construction Trends. Accessible from [2018-06-18] https://www.hydroworld.com/articles/hr/print/volume-27/issue-7/technical-articles/roller-compacted-concrete-dams-design-and-construction-trends.html
ACI (2017): ACI mix design. Accessible from [2018-04-08]http://www.ce.memphis.edu/1112/notes/project_2/beam/ACI_mix_design.pdf
ACI (2011): Report on Roller-Compacted Mass concrete, ACI 2017.5R-11, American Concrete Institute.
Amberg F (2003): Thermal Analysis of a RCC dam during construction. Accessible from [2018-06-18] https://www.lombardi.ch/it-it/SiteAssets/Publications/1198/Pubb-0378-L-Thermal%20analysis%20of%20a%20RCC%20dam%20during%20construction.pdf
Andersson O & Seppälä M (2015): Verification of the response of a concrete arch dam subjected to seasonal temperature variations, MSc Thesis, TRITA-BKN MSc Thesis 458, KTH Royal Institute of Technology
ASDSO (2017): What are the different types of dams and how do they work?. Association of State Dam Safety Officials. Available from [accessed 2018-01-24]https://damsafety.org/different-types-dams
ASTM C494 (2018): Standard Specification for Chemical Admixtures for Concrete, American Society for Testing and Materials.
ASTM C618 (2018): Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete, American Society for Testing and Materials.
Barcelo L, Clavaud B, Moranville M (2005): Autogenous shrinkage of concrete: a balance between autogenous swelling and self-destruction. Cement concrete research 35.
BASF (2014): Concrete Technology in focus – Shrinkage of concrete. Accessible from [2018-06-12]https://assets.master-builders-solutions.basf.com/Shared%20Documents/EB%20Construction%20Chemcials%20-%20US/Admixture%20Systems/Brochures/Shrinkage_Of_Concrete_CTIF.pdf
Beene R.R.W, Stroman W.R, Thornhill P.D (1988): Kerrville Ponding Dam, Guadalupe River, Texas. Missouri University of Science and Technology.
Berga L, Buil J.M, Jofré C, Chonggang S (2003): Roller compacted Concrete Dams. Netherlands . p 390.
66
Broberg L, Thorwid M (2015): Evaluation of failure modes for concrete dams, MSc Thesis, TRITA-BKN. Master Thesis 455, KTH Royal Institute of Technology
Chryso (2018): Roller Compacted Concrete. Accessible from [2018-05-03] http://za.chryso.com/p/6465/4/1668/en
Cotoi T (2015): Dam engineering GRV BUTT. Available from [accessed 2018-05-10] http://www.scribd.com/doc/280436707/Dam-Engineering-GRV-BUTT
Eriksson D (2018): Numerical models for degradation of concrete in hydraulic structures due to long-term contact with water, Licentiate thesis, TRITA-ABE-DLT-185, KTH Royal Institute of Technology.
Eurocode 2 (2008): Design of concrete structures. Part 1-1: General rules and rules for buildings. SS EN 1992-1-1:2005, SIS.
Griggs T, Herweynen R (2012): Unique challenges influencing the design and construction of three recent Australian RCC dams. International Commission of Large Dams (ICOLD).
Hansen K.D & Reinhardt W.G (1991): Roller-Compacted Concrete Dams. McGraw-Hill, Inc.
Harrington D, Abdo F, Adaska W, Hazaree C (2010): Guide for Roller Compacted Concrete Pavement. Accessible from [2018-05-17]https://www.irmca.com/wp-content/uploads/2014/12/cp_tech_center_-_rcc_guide.pdf
Headwaters Resources (2017): Fly ash types & benefits, Technical Bulletin, Headwaters Resources. Accessible from [2018-01-25]http://flyash.com/data/upfiles/resource/TB%201%20Fly%20Ash%20Types%20&%20Benefits%202015_2.pdf
Hylte (2018): Ombyggnad av Hylte damm och Jakobs sjö. Accessible from [2018-05-21]http://www.hylte.se/byggabomiljo/energiochklimat/dammprojektet.4.77497d4f15515b08358f88.html
ICOLD (2003): Roller-compacted concrete dams – State of the art and case histories, Bulletin 126, International Commission of Large Dams (ICOLD).
Jennings H, Thomas J (2010): 3.8 Types of Portland cement. Accessible from [2018-03-17] http://iti.northwestern.edu/cement/monograph/Monograph3_8.html
Leclerc M, Léger P, Tinawi R (2001) : Cadam User´s Manual. Montréal, version 1.4.3.
Maxi (2017): What concrete slump do you need for your project?. Accessible from [2018-06-10] https://maxi.co.uk/what-concrete-slump/
PCA (2010): Guide for Roller Compacted concrete pavements. Accessible from [2018-06-13]http://cncement.org/wp-content/uploads/2014/08/A-SR298-Guide-to-RCC-Pavements-8-10_21.pdf
PCA (2018): How Concrete is made. Accessible from [2018-04-20]http://www.cement.org/cement-concrete-applications/how-concrete-is-made
67
PCA (2004): Roller-Compacted Concrete Density: Principles and Practices. Accessible from [2018-04-28] http://rccpavementcouncil.org/wp-content/uploads/2016/06/RCC-Density-Principles-Practices.pdf
RIDAS (2017): Swedish Hydropower companies guidelines for dam safety; application guideline 7.3 Concrete dams (In Swedish). Svensk energi.
Roller Compacted Concrete (2013): Mix Design. Accessible from [2018-03-15] http://www.rollercompacted.org/mixdesign.html
Rosenqvist M (2016): Frost-induced deterioration of concrete in hydraulic structures, MSc Thesis, ISRN LUTVDG/TVBM. Lund University
Shaw Q.H.W (2010): A new understanding of the early behaviour of Roller Compacted concrete in large dams. PhD Thesis. University of Pretoria.
SWECO (2014): PM- Geoteknik. Statkraft Sverige AB
SWECO (2013): Markteknisk undersökningsrapport (MUR). Statkraft Sverige AB.
The Constructor (2017): Roller Compacted Concrete. Accessible from [2018-05-19] https://theconstructor.org/concrete/roller-compacted-concrete-pavement-dams/5863/
The Concrete Society (2018): Vebe test. Accessible from [2018-05-16] http://www.concrete.org.uk/fingertips-nuggets.asp?cmd=display&id=979#
USACE (2000): Roller compacted concrete, EM 1110-2-2006. US Army Corps Engineers.
USBR (2017): Design and Construction Considerations for Hydraulic structures – Roller compacted concrete, Second edition. US Department of the Interior Bureau of Reclamation.
USBR (2006): State-of-Practice for the Nonlinear Analysis of Concrete, US Bureau of Reclamation
Vattenkraft.info (2009): Info om Svensk vattenkraft. Accessible from [2018-06-10] https://vattenkraft.info/?page=23
Water Power (2009): Building an RCC dam in the Jordan valley. Accessible from [2018-05-03]http://www.waterpowermagazine.com/features/featurebuilding-an-rcc-dam-in-the-jordan-valley/
Wikiwand (2018): Dam. Accessible from [2018-06-10] http://www.wikiwand.com/en/Dam
68
69
A
CADAM & calculation
Appendix
CADAM - Model parameters
L1 = 11,600 m
L2 = 0,000 m
L3 = 5,300 m
L4 = 5,300 m
Elev. A = 0,000 m
Elev. B = 0,000 m
Elev. C = 0,000 m
Elev. D = 0,000 m
Elev. E = 9,500 m
Elev. F = 9,500 m
Elev. G = 9,500 m
Elev. H = 0,000 m
Elev. I = 0,000 m
2400,00 kg/m³
CADAM - Model parameters
Joint 30000,0 0,000 0,000 35,000 0,000 Option 2
0,000 35,000 0,000 Option 2
Peak:
Residual:
Base joint 30000,0 0,000 0,000 37,000 0,000 Option 2
0,000 37,000 0,000 Option 2
Peak:
Residual:
1 Joint 9,300 0,000 13,361325 9,300 5,433 5,433
2 Joint 9,000 0,000 14,883644 9,000 5,632 5,632
3 Joint 8,700 0,000 16,517413 8,700 5,831 5,831
4 Joint 8,400 0,000 18,266568 8,400 6,029 6,029
5 Joint 8,100 0,000 20,135047 8,100 6,228 6,228
6 Joint 7,800 0,000 22,126786 7,800 6,427 6,427
7 Joint 7,500 0,000 24,245723 7,500 6,626 6,626
8 Joint 7,200 0,000 26,495795 7,200 6,825 6,825
9 Joint 6,900 0,000 28,880939 6,900 7,024 7,024
10 Joint 6,600 0,000 31,405093 6,600 7,223 7,223
11 Joint 6,300 0,000 34,072193 6,300 7,422 7,422
12 Joint 6,000 0,000 36,886176 6,000 7,621 7,621
13 Joint 5,700 0,000 39,850981 5,700 7,820 7,820
14 Joint 5,400 0,000 42,970543 5,400 8,019 8,019
15 Joint 5,100 0,000 46,248801 5,100 8,218 8,218
16 Joint 4,800 0,000 49,689691 4,800 8,417 8,417
17 Joint 4,500 0,000 53,297150 4,500 8,616 8,616
18 Joint 4,200 0,000 57,075117 4,200 8,815 8,815
19 Joint 3,900 0,000 61,027527 3,900 9,014 9,014
20 Joint 3,600 0,000 65,158318 3,600 9,213 9,213
CADAM - Model parameters
21 Joint 3,300 0,000 69,471427 3,300 9,412 9,412
22 Joint 3,000 0,000 73,970792 3,000 9,611 9,611
23 Joint 2,700 0,000 78,660350 2,700 9,809 9,809
24 Joint 2,400 0,000 83,544037 2,400 10,008 10,008
25 Joint 2,100 0,000 88,625791 2,100 10,207 10,207
26 Joint 1,800 0,000 93,909549 1,800 10,406 10,406
27 Joint 1,500 0,000 99,399249 1,500 10,605 10,605
28 Joint 1,200 0,000 105,09883 1,200 10,804 10,804
29 Joint 0,900 0,000 111,01222 0,900 11,003 11,003
30 Joint 0,600 0,000 117,14337 0,600 11,202 11,202
31 Joint 0,300 0,000 123,49620 0,300 11,401 11,401
32 Base joint 0,000 0,000 130,07467 0,000 11,600 11,600
1 Joint 9,300 9,300
2 Joint 9,000 9,000
3 Joint 8,700 8,700
4 Joint 8,400 8,400
5 Joint 8,100 8,100
6 Joint 7,800 7,800
7 Joint 7,500 7,500
8 Joint 7,200 7,200
9 Joint 6,900 6,900
10 Joint 6,600 6,600
11 Joint 6,300 6,300
12 Joint 6,000 6,000
13 Joint 5,700 5,700
14 Joint 5,400 5,400
15 Joint 5,100 5,100
16 Joint 4,800 4,800
17 Joint 4,500 4,500
18 Joint 4,200 4,200
19 Joint 3,900 3,900
20 Joint 3,600 3,600
21 Joint 3,300 3,300
22 Joint 3,000 3,000
23 Joint 2,700 2,700
24 Joint 2,400 2,400
25 Joint 2,100 2,100
26 Joint 1,800 1,800
27 Joint 1,500 1,500
28 Joint 1,200 1,200
CADAM - Model parameters
29 Joint 0,900 0,900
30 Joint 0,600 0,600
31 Joint 0,300 0,300
32 Base joint 0,000 0,000
8,200 0,000
9,000 0,000
0,600
0,000
Assumption: At rest
Elev. =
9,810 kN/m³ 50,000 kN
m
Load =
Thickness =
7,000
20,000
m
kN/m³
deg
m m
m m
Elevation = 7,900 m
100,00%
50,00%
Load =
Apply at elev. =
Max. elevation = 2,000
-1,000
0,000 kN
m
m
Crack initiation: ft / 2,000
Cracking is considered for all combinations ?
ft /10,000Crack propagation:
Dynamic magnification:
YES
Static analyses:
Seismic analyses:
Drain effectivness:
Convergence method:
Accuracy:
Full uplift pressures applied to the crack section
Uplift pressures remain unchanged
No drain effectiveness upon cracking
Bracketing + Bi-section method
Medium (1E-6)
ft = 0
ft = 0
ft / 1,000
ft /10,000
ft * 1,500
ft / 3,000
ft /10,000
Post-seismic analyses: Full uplift pressures applied to the crack section
Downstream closed crack:Restore uncracked uplift condition
0,000 0,000 0,000 UniformkN 0,000Ice load
CADAM - Model parameters
Upstream Crack Length (% of Joint)
Sliding Safety Factor (Peak)
Sliding Safety Factor (Residual)
Downstream Crack Length (% of Joint)
Overturning Safety Factor (Toward U/S)
Number of analyses
50000
Load combination
Overturning Safety Factor (Toward D/S)
Normal
joint considered
Base joint
Uplifting Safety Factor
Maximuim Normal Compressive Stress
Maximuim Normal Tensile Stress
Resultant Position (% of Joint from U/S)
Final Uplift Force
Output parameters:
Input parameters: Statistic.in
Statistic.out
Upstream Crack Length (% of Joint)
Sliding Safety Factor (Peak)
Sliding Safety Factor (Residual)
Downstream Crack Length (% of Joint)
Overturning Safety Factor (Toward U/S)
Incremental load = Normal Upstream Reservoir Elevation
Load combination =
Overturning Safety Factor (Toward D/S)
Usual combination
joint considered = # 31 Elev.= 0,000
Uplifting Safety Factor
Maximum Normal Compressive Stress
Maximum Normal Tensile Stress
Resultant Position (% of Joint from U/S)
File name = Incremental.out
First step = 8,200
Last step = 15,000
Increment by = 0,100
m
m
m
Perform Analyses = Yes
CA
DA
M -
Resu
lts r
ep
ort
1,0000
1,0000
1,0000
1,0000
1,0000
1,0000
1,0000
1,0000
1,0000
2,0000
1,5000
1,5000
1,3000
1,3000
1,1000
1,3500
1,3500
1,0000
1,0000
1,1000
1,5000
1,5000
1,1000
1,1000
1,1000
1,0000
1,0000
1,1000
1,1000
66,7
0,0
50,0
90,9
90,9
66,7
33,3
50,0
90,9
90,9
CA
DA
M -
Resu
lts r
ep
ort
1
9,300
-4,821
-4,482
0,000
-9990,000
2
9,000
-12,424
-10,427
0,000
-9990,000
3
8,700
-20,393
-15,563
0,000
-9990,000
4
8,400
-28,653
-20,011
0,000
-9990,000
5
8,100
-36,097
-23,932
0,000
-3,542
0,000
-9990,000
15,871
29,929
6
7,800
-40,906
-28,199
0,000
-0,318
0,000
-9990,000
18,700
11,445
7
7,500
-44,950
-32,934
0,000
21,840
0,000
-9990,000
21,840
100,000
8
7,200
-49,020
-37,371
0,000
-0,016
0,000
-9990,000
24,783
2,492
9
6,900
-53,282
-41,368
0,000
-0,198
0,000
-9990,000
27,433
7,808
10
6,600
-57,675
-45,005
0,000
-0,397
0,000
-9990,000
29,846
10,283
11
6,300
-62,149
-48,352
0,000
-0,532
0,000
-9990,000
32,065
11,331
12
6,000
-66,663
-51,466
0,000
-0,587
0,000
-9990,000
34,130
11,509
13
5,700
-71,183
-54,395
0,000
-0,568
0,000
-9990,000
36,073
11,073
14
5,400
-75,682
-57,180
0,000
-0,490
0,000
-9990,000
37,920
10,147
15
5,100
-80,139
-59,854
0,000
-0,372
0,000
-9990,000
39,693
8,789
16
4,800
-84,536
-62,447
0,000
-0,237
0,000
-9990,000
41,412
7,017
17
4,500
-88,857
-64,981
0,000
-0,111
0,000
-9990,000
43,093
4,825
18
4,200
-93,093
-67,478
0,000
-0,022
0,000
-9990,000
44,748
2,183
19
3,900
-97,234
-69,954
0,000
46,391
0,000
-9990,000
46,391
100,000
20
3,600
-101,274
-72,424
0,000
48,029
0,000
-9990,000
48,029
100,000
21
3,300
-105,206
-74,900
0,000
49,671
0,000
-9990,000
49,671
100,000
22
3,000
-109,028
-77,393
0,000
51,323
0,000
-9990,000
51,323
100,000
23
2,700
-112,736
-79,909
0,000
52,992
0,000
-9990,000
52,992
100,000
24
2,400
-116,328
-82,457
0,000
54,682
0,000
-9990,000
54,682
100,000
25
2,100
-119,805
-85,043
0,000
56,397
0,000
-9990,000
56,397
100,000
26
1,800
-123,165
-87,671
0,000
58,140
0,000
-9990,000
58,140
100,000
27
1,500
-126,409
-90,345
0,000
59,913
0,000
-9990,000
59,913
100,000
28
1,200
-129,537
-93,069
0,000
61,719
0,000
-9990,000
61,719
100,000
29
0,900
-132,550
-95,845
0,000
63,560
0,000
-9990,000
63,560
100,000
30
0,600
-135,451
-98,674
0,000
65,437
0,000
-9990,000
65,437
100,000
31
0,300
-138,239
-101,560
0,000
67,350
0,000
-9990,000
67,350
100,000
32
Base joint
-129,287
-133,097
0,000
88,265
0,000
-9990,000
88,265
100,000
CA
DA
M -
Resu
lts r
ep
ort
1
9,300
> 100
> 100
> 100
> 100
> 100
-0,8
0,00
-25,27
0,00
49,39217
0,000
2
9,000
> 100
> 100
> 100
> 100
> 100
-5,3
0,00
-64,34
0,00
48,54292
0,000
3
8,700
> 100
> 100
> 100
> 100
> 100
-13,7
0,00
-104,82
0,00
47,76136
0,000
4
8,400
> 100
> 100
> 100
> 100
> 100
-26,2
0,00
-146,71
0,00
47,04030
0,000
5
8,100
15,61592
15,61592
86,58707
48,42974
62,19152
-39,3
8,38
-186,94
3,06
46,62252
0,000
6
7,800
4,55780
4,55780
25,79716
13,45678
18,61091
-43,7
34,12
-222,08
12,61
46,93523
0,000
7
7,500
3,44792
3,44792
17,13774
8,42485
12,34177
-44,0
52,40
-258,04
22,75
47,42866
0,000
8
7,200
3,75987
3,75987
13,61595
6,56363
9,80643
-45,2
54,91
-294,82
33,48
47,75280
0,000
9
6,900
3,99322
3,99322
11,66552
5,61952
8,42176
-49,0
58,29
-332,42
44,79
47,90205
0,000
10
6,600
4,15085
4,15085
10,40912
5,04559
7,54182
-55,1
62,56
-370,84
56,69
47,94345
0,000
11
6,300
4,24090
4,24090
9,52265
4,65686
6,92850
-63,3
67,71
-410,08
69,17
47,91904
0,000
12
6,000
4,27430
4,27430
8,85819
4,37357
6,47351
-73,6
73,74
-450,13
82,24
47,85593
0,000
13
5,700
4,26266
4,26266
8,33839
4,15580
6,12043
-85,5
80,66
-491,01
95,89
47,77197
0,000
14
5,400
4,21690
4,21690
7,91870
3,98142
5,83700
-99,1
88,46
-532,71
110,13
47,67902
0,000
15
5,100
4,14649
4,14649
7,57157
3,83721
5,60339
-114,2
97,14
-575,23
124,96
47,58503
0,000
16
4,800
4,05919
4,05919
7,27897
3,71485
5,40674
-130,4
106,70
-618,56
140,37
47,49528
0,000
17
4,500
3,96111
3,96111
7,02858
3,60883
5,23832
-147,7
117,15
-662,72
156,36
47,41326
0,000
18
4,200
3,85690
3,85690
6,81164
3,51536
5,09203
-165,9
128,48
-707,70
172,95
47,34122
0,000
19
3,900
3,75000
3,75000
6,62176
3,43179
4,96341
-184,7
140,69
-753,49
190,11
47,28050
0,000
20
3,600
3,64290
3,64290
6,45411
3,35619
4,84918
-204,0
153,79
-800,11
207,86
47,23185
0,000
21
3,300
3,53734
3,53734
6,30501
3,28712
4,74683
-223,7
167,77
-847,54
226,20
47,19558
0,000
22
3,000
3,43449
3,43449
6,17158
3,22352
4,65444
-243,5
182,63
-895,80
245,13
47,17171
0,000
23
2,700
3,33511
3,33511
6,05151
3,16454
4,57047
-263,2
198,38
-944,87
264,64
47,16002
0,000
24
2,400
3,23967
3,23967
5,94294
3,10953
4,49372
-282,7
215,00
-994,77
284,73
47,16018
0,000
25
2,100
3,14841
3,14841
5,84436
3,05798
4,42321
-301,8
232,52
-1045,48
305,41
47,17174
0,000
26
1,800
3,06142
3,06142
5,75451
3,00946
4,35812
-320,3
250,91
-1097,01
326,68
47,19419
0,000
27
1,500
2,97868
2,97868
5,67235
2,96365
4,29780
-338,0
270,19
-1149,37
348,53
47,22701
0,000
28
1,200
2,90010
2,90010
5,59699
2,92024
4,24168
-354,7
290,34
-1202,54
370,96
47,26962
0,000
29
0,900
2,82553
2,82553
5,52767
2,87902
4,18930
-370,3
311,39
-1256,53
393,98
47,32148
0,000
30
0,600
2,75481
2,75481
5,46375
2,83977
4,14026
-384,6
333,31
-1311,35
417,59
47,38202
0,000
31
0,300
2,68776
2,68776
5,40468
2,80234
4,09422
-397,3
356,12
-1366,98
441,79
47,45069
0,000
32
Base joint
3,01933
3,01933
5,91636
2,79095
4,26178
42,7
379,81
-1521,83
466,56
50,24206
0,000
1,500
1,350
1,500
1,500
1,000
CA
DA
M -
Resu
lts r
ep
ort
U/S crack length (% of joint)
0,000
0,000
0,000
0,000
1,00000
0,00000
D/S crack lenght (% of joint)
0,000
0,000
0,000
0,000
1,00000
0,00000
Sliding Safety Fact. peak
3,017
0,074
2,688
3,187
1,00000
0,00000
Sliding Safety Factor (residual)
3,017
0,074
2,688
3,187
1,00000
0,00000
Overturning Safety Factor toward U/S
5,919
0,041
5,829
6,121
1,00000
0,00000
Overturning Safety Factor toward D/S
2,789
0,042
2,595
2,884
1,00000
0,00000
Uplifting Safety Factor
4,262
0,000
4,262
4,262
1,00000
0,00000
Maximum Normal Stress
-134,325
2,350
-149,594
-131,192
-
-
Minimum Normal Stress
-128,059
2,350
-131,192
-112,790
-
-
Resultant position (% of joint)
50,266
0,420
49,347
52,338
-
-
Final Uplift Force
466,564
0,000
466,564
466,564
-
-
CA
DA
M -
Resu
lts r
ep
ort
8,200
0,000
0,000
3,019
3,019
4,262
2,791
5,916
-129,287
-133,097
50,242
8,300
0,000
0,000
2,945
2,945
4,210
2,745
5,866
-126,594
-134,809
50,524
8,600
0,000
0,000
2,737
2,737
4,064
2,613
5,725
-118,297
-140,163
51,410
8,800
0,000
0,000
2,608
2,608
3,971
2,530
5,638
-112,578
-143,920
52,037
9,000
0,000
0,000
2,487
2,487
3,883
2,450
5,557
-106,705
-147,831
52,693
9,300
0,000
0,000
2,319
2,319
3,758
2,337
5,446
-97,599
-153,994
53,736
9,500
0,000
0,000
2,215
2,215
3,679
2,266
5,377
-91,326
-158,305
54,472
9,700
0,000
0,000
1,968
1,968
3,369
2,175
4,651
-98,450
-131,659
52,405
9,900
0,000
0,000
1,880
1,880
3,252
2,109
4,442
-93,903
-133,694
52,914
10,200
0,000
0,000
1,936
1,936
3,094
2,175
3,976
-109,091
-114,823
50,427
10,400
0,000
0,000
1,853
1,853
2,998
2,114
3,824
-104,912
-116,601
50,879
10,600
0,000
0,000
1,776
1,776
2,909
2,056
3,687
-100,711
-118,447
51,349
10,900
0,000
0,000
1,673
1,673
2,788
1,976
3,504
-94,380
-121,330
52,082
11,100
0,000
0,000
1,611
1,611
2,713
1,927
3,396
-90,145
-123,322
52,590
11,300
0,000
0,000
1,553
1,553
2,644
1,881
3,296
-85,907
-125,362
53,113
11,500
0,000
0,000
1,500
1,500
2,579
1,837
3,205
-81,668
-127,448
53,649
11,800
0,000
0,000
1,426
1,426
2,489
1,777
3,081
-75,323
-130,648
54,477
12,000
0,000
0,000
1,382
1,382
2,434
1,740
3,006
-71,108
-132,822
55,044
12,200
0,000
0,000
1,340
1,340
2,382
1,704
2,936
-66,911
-135,022
55,622
12,500
0,000
0,000
1,283
1,283
2,309
1,655
2,839
-60,660
-138,363
56,507
12,700
0,000
0,000
1,248
1,248
2,264
1,624
2,780
-56,531
-140,609
57,108
12,900
0,000
0,000
1,214
1,214
2,221
1,595
2,724
-52,437
-142,863
57,717
13,200
0,000
0,000
1,169
1,169
2,162
1,555
2,647
-46,374
-146,252
58,642
13,400
0,000
0,000
1,141
1,141
2,125
1,529
2,599
-42,392
-148,507
59,265
13,600
0,000
0,000
1,114
1,114
2,090
1,505
2,553
-38,463
-150,754
59,891
13,900
0,000
0,000
1,077
1,077
2,040
1,472
2,489
-32,680
-154,098
60,834
14,100
0,000
0,000
1,055
1,055
2,010
1,451
2,449
-28,907
-156,301
61,464
14,300
0,000
0,000
1,033
1,033
1,980
1,431
2,411
-25,204
-158,479
62,093
14,500
0,000
0,000
1,013
1,013
1,952
1,412
2,374
-21,578
-160,625
62,719
14,800
0,000
0,000
0,985
0,985
1,913
1,385
2,322
-16,291
-163,775
63,651
15,000
0,000
0,000
0,968
0,968
1,889
1,369
2,289
-12,877
-165,822
64,265
CA
DA
M -
Sta
bil
ity
dra
win
g
Usu
al c
ombi
natio
n (e
ffect
ive
stre
ss a
naly
sis)
Join
t #C
rack
Nor
mal
Prin
cipa
lU
plift
(% jo
int)
(kPa
)(k
Pa)
(kPa
)C
rack
Nor
mal
Prin
cipa
lU
plift
(% jo
int)
(kPa
)(k
Pa)
(kPa
)
CA
DA
M -
Sta
bil
ity
dra
win
g
Usu
al c
ombi
natio
n (s
tabi
lity
anal
ysis
)
Join
t #SS
FSS
FO
SFO
SFU
SFN
orm
alSh
ear
Mom
ent
Res
. Pos
.(p
eak)
(res
idua
l)(U
/S <
-)(->
D/S
)(k
N)
(kN
)(k
Nm
)(%
join
t)
1,5
00 1
,350
1,5
00 1
,500
1,0
00
γ
γ
γ
γ
γ
γ
γ
γ
γ
γ
γ
γ
γ
γ
γ
γ
γ
γ
www.kth.se
TRITA-ABE-MBT-18366ISBN 978-91-7729-869-4
