Reinforced Earth Wall

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INDEX

1.1 Introduction:- ..................................................................................................................... 11.2 Components of RE Wall:-................................................................................................... 1

1.3 Batter in RE Wall:- ............................................................................................................. 1

1.4 Procedure:- ......................................................................................................................... 2

1.4.1 Excavation & Ground Preparation:- .................................................................................... 2

1.4.1.1 Purpose .......................................................................................................................... 2

1.4.1.2 Excavation ..................................................................................................................... 3

1.4.2 Construction of Leveling Pad:- .......................................................................................... 3

1.4.3 Placement of Fill up to the top of the Leveling Pad:- .......................................................... 31.4.4 Casting, Curing & Handling of Modular Blocks:- ............................................................... 3

1.4.4.1 Mix Design .................................................................................................................... 3

1.4.4.2 Casting ........................................................................................................................... 4

1.4.4.3 Curing ............................................................................................................................ 4

1.4.4.4 Transportation ................................................................................................................ 5

1.4.5 Erection of First Course of Modular Blocks:- ..................................................................... 5

1.4.6 Erection of subsequent Courses of Modular Blocks:- .......................................................... 5

1.4.7 Placement of filter media:- ................................................................................................. 61.4.8 Placement & Compaction of Fill:- ...................................................................................... 6

1.4.8.1 Types of Materials ......................................................................................................... 6

1.4.8.2 Precautions to be taken when Different Types of Fill Materials are Used........................ 7

1.4.8.3 Placing, Spreading, Leveling and Compaction of Fill ..................................................... 8

1.4.8.4 Compaction Equipment .................................................................................................. 9

1.4.8.5 Relative Compaction ...................................................................................................... 9

1.4.9 Installing The Geogrid Reinforcement:- .............................................................................. 9

1.4.10 Placement of Drainage Bay:- ............................................................................................ 11

1.4.11 Casting of Coping Beam:- ................................................................................................ 11

1.4.12 Quality Control:- .............................................................................................................. 11


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REINFORCED EARTH WALL

Efforts By: UC 3406

School Of Building Science and Technology, CEPT University2

1.4 Procedure:-

1.4.1 Excavation & Ground Preparation:-

1.4.1.1 Purpose1) To provide the required embedment for the reinforced soil wall (RSW) below the

existing/finished ground / service road level. The minimum embedment depth measured

from the bottom of the leveling pad is 1.0 m (except in the case of a competent rock stratum

being encountered at shallower depths).

2) To remove all kinds of unsuitable soils and other materials which could have a deleteriousimpact on the constructability, stability, serviceability and durability of the RSW and

associated works - loose uncontrolled fills, degradable materials like waste, rubbish etc.,

construction debris, organic soils like peat, excessively soft and compressible soils like clays

and silts, soils prone to collapse under wetting

3) To ensure that the founding stratum and the underlying strata would be able to support the

Excavation

Leveling Pad

Block Erection

Filter Media

Soil Fill

Placing of Geogrid

Coping


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imposed loads without undergoing sliding, bearing, or deep seated rotational failure and the

resulting vertical and horizontal deformations of the ground will be within permissible limits.

4) To ensure that the foundation soils would not undergo liquefaction during earthquakes.1.4.1.2 Excavation

Mark the lines of excavation on the ground as shown in drawings. The required depth of

excavation is generally kept at 1000 mm below the OGL. Excavate the ground to the required width

and depth.

1.4.2 Construction of Leveling Pad:-

Mark the centre-line of the leveling pad on the prepared ground surface. The RSW facing

has to be erected with a built-in inward batter of 4. To accommodate this batter, the bottom of

the facing has to move out in plan, with respect to the top of the facing by an offset distance,

which varies with the wall facing height. The required offset distances are shown in the

corresponding longitudinal section drawings. Hence the centerline of the leveling pad has to be

fixed considering this offset distance.

Inspect the ground surface along the line of the leveling pad to ensure that the soil is firm,

level and flat. Check the level so that the grade corresponds to the Bottom of leveling pad levels

shown on the corresponding longitudinal section drawings. Erect side forms and cast the leveling

pad with dimensions of 600 m width and 200 mm thickness with concrete of grade M15. The

leveling pad should be finished to a tolerance of 3-5 mm and cured for 24 hours prior to

commencement of placement of facing units.

1.4.3 Placement of Fill up to the top of the Leveling Pad:-

Place and compact select fill up to the top of the leveling pad, with a relative compaction of

95% of MDD.

1.4.4 Casting, Curing & Handling of Modular Blocks:-

1.4.4.1 Mix DesignThe concrete required for casting of modular blocks shall essentially be of M-35 grade and

zero slump concrete. The mix design shall be done by using Standard Indian Codes like IS 10262

or SP 23. Since, the casting is being done by dry casting technique, adequate care shall be taken


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to achieve a smooth fascia and clear edges. Trial modular blocks may be produced to assure

finishing of the blocks and thereafter the Mix Design may be fine-tuned to perfection keeping the

required Characteristic Strength intact.

Laboratory Cube Moulds (6 Nos) shall be casted for every 1000 numbers of modular blocks

produced. While casting these cubes may be compacted using tamping rods or machine vibration

(Casting Machine). These cubes shall be tested for their compressive strengths for 7 and 28 days.

1.4.4.2 CastingCasting of blocks shall be done by using Modular Block Casting Machine. The machine shall

have an efficient inbuilt vibrator to produce sufficient vibration required achieve desired finish.

Each block produced from the machine shall be duly inspected by the incharge, blow holes/honey

combs, if any, appearing on the block fascia shall be repaired / finished by using the slurry produced

during vibration and get deposited on the base plate. This will ensure homogeneous appearance of

the block. The Top of Fascia shall be smoothened by using neat cement slurry. Any unwanted

projection of aggregated over the top of modular blocks shall be removed while in green stage only.

1.4.4.3 CuringProduced blocks shall be stacked upto a height of 600 mm or three layers. Once the stacking

is completed, the entire stacking shall be covered by using Hessian Cloth. In summer, the Hessiancloth shall be dripped wet over it, also for better result sprinkler system can be used. The curing

period will be at least every three hours, for a minimum of 7 days. In winter, the wetting may be

delayed as per requirement. Curing of the blocks shall start after immediately after the Modular

blocks are stripped of from the base plate.

Blocks Stacked in Three Layers

Dripped Wet Hessian Cloth

GL

Adequate Drainage


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1.4.4.4 TransportationBlocks shall be transferred to respected sites by using tractor trollys or trucks. They will

loaded or unloaded manually, only.

1.4.5 Erection of First Course of Modular Blocks:-

1)The first course of modular blocks is directly placed on the leveling pad. Check the topsurface of the leveling pad over a width of 300 mm at the center for flatness with a 3 m long

straight edge. Fill any minor irregularities or undulations with a thin layer of stiff cement

mortar. Check the level with a 1200 mm long spirit level.

2)On the top surface of the leveling pad mark a chalk line corresponding to the rear face of thefirst course of modular blocks.

3)Position the first row of modular blocks on the leveling pad with their rear face aligned alongthe chalk line and with ends butting with each other. Care may be taken to ensure that the

blocks are evenly bedded on the leveling pad along their length. If required a thin layer of

stiff cement mortar or rubber shims may be used to ensure proper bedding of blocks on the

leveling pad.

4)Stretch a string along the rear face top edge of the modular blocks and adjust the blocks sothat they are correctly aligned. Check the level with a 1200 mm long spirit level.

1.4.6 Erection of subsequent Courses of Modular Blocks:-

1)Subsequent course of blocks are erected in a repetitive sequence after filling to the top ofthe previous course has been completed and the specified geogrid reinforcements have

been positioned on top of the blocks of the previous course.

2)Successive courses are placed in a running bond configuration.3)Before placing each course, clean the top surface of the blocks of previous course by

removing any fill, aggregate etc. with a wire brush or stiff broom and ensure that the top of

the blocks of previous course are level using a spirit level.

4)Geogrids of the required type and length should be positioned. The blocks should be placedover the geogrid and adjusted so that the tongue and grooved joints engage ensuring the

required setback.


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5)Stretch a string along the rear face top edge of the modular blocks and adjust the blocks sothat they are correctly aligned. Check the level with a spirit level.

1.4.7 Placement of filter media:-

Filter Media MSA 20 mm is provided between the blocks and 600 mm behind them. Thickness is 200 mm Plate Compactor is used for compaction It allows the drainage of trapped water from the wall to avoid development of pore water

pressure.

Soil filling is then done with the following sequence of passes using a 10T vibratory roller:

Sr. No. Types of Passes Numbers

1 Static 1

2 Low vibration 2

3 High vibration 2

4 Low vibration 2

5 Static pass 1

After the 1st pass, watering is done.1.4.8 Placement & Compaction of Fill:-

1.4.8.1 Types of MaterialsThe materials used in the different zones of the approach are:

1) Drainage Media / Unit Fill: For the 300 mm thick drainage layer placed behind the facingblocks and for filling of the spaces between the segmental blocks, well graded aggregates of

size 10 to 20 mm shall be used.

2)Reinforced Fill: Select granular fill with peak effective angle of shearing resistance ( ) 30,Fines (Passing 75 micron sieve) 10 %, Coefficient of Uniformity (Cu) 2, Maximum particle

size (Dmax) 40 mm (100 % passing 40 mm sieve), D80 25 mm (80 % or more passing 25

mm sieve), Plasticity index 6 % in the geogrid reinforced soil zone.


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3)Retained Fill: Soil behind the reinforced fill whose properties have an effect on the maximumearth pressure exerted on the reinforced soil mass is defined as retained fill. This zone is

approximately considered as the region enclosed by the vertical plane at the back of the

reinforced soil mass and a plane inclined at 45 to this face. In this zone a select fill with

30 (as considered in the design of reinforced soil walls) should be used. Reinforced fill could

always be used as retained fill. However, when a material other than reinforced fill is used in

the retained fill zone, care should be taken to ensure that the design value is achieved.

Maximum particle size shall be limited to 75 mm, liquid limit and plasticity index shall not

exceed 50 and 25 respectively. Material with maximum particle size (Dmax) 40 mm (100 %

passing 40 mm sieve), D80 25 mm (80 % or more passing 25 mm sieve) may be used as

retained fill.

4)Embankment Fill: Behind the retained fill zone, normal fill material conforming to therequirements of MORTH Specifications clause 305.2 may be used. Material with maximum

particle size (Dmax) 40 mm (100 % passing 40 mm sieve), D80 25 mm (80 % or more

passing 25 mm sieve) may be used as embankment fill.

5)Pavement Subgrade: In this zone, materials conforming to the requirements of subgradeshould be used. However, if geogrid reinforcement has to be provided within the subgrade,

then this should satisfy the requirements for reinforced fill also.

1.4.8.2 Precautions to be taken when Different Types of Fill Materials are UsedWhen different types of fill materials are used in different zones certain precautions should

be taken.

1. The zones in which different materials have to be placed should be clearly delineated foreach lift, before the commencement of earth work

2. Strict control must be exercised during all stages of dumping, spreading, grading andcompaction of fill materials to ensure that there is no mixing or contamination of a higher

quality material with a lower quality material.

3. Natural and optimum moisture contents of different materials could be different and hencethe amount of watering needed could be different. Care must be taken to ensure that

proper control of moisture is established.

4.

Compaction equipment and method (operating frequency, number of passes etc.) should


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be fine-tuned, depending on the requirements of the different materials.

1.4.8.3 Placing, Spreading, Leveling and Compaction of Fill1. All construction plant and equipment with a mass more than 1500 Kg. shall be kept at all

times 1.5 m away from the rear face of the panels.

2. Construction equipment shall not be permitted to move directly over the geogrid. At anytime, maintain a minimum compacted soil cover of 150 mm between the geogrid and the

wheel/track of construction equipment. Turning of construction vehicles should be avoided

on the first lift immediately above the geogrid. As far as possible avoid sudden stoppage of

the equipment.

3. The deposition and compaction should be carried out so that all layers of geogridreinforcements are fixed at the levels as shown in the drawings.

4. The deposition, spreading, leveling and compaction of the fill should be carried out generallyin a direction parallel to the facing and should be executed in stages to alternate with the

placing and fixing of modular blocks and geogrid reinforcements.

5. Care must be taken to ensure that the modular blocks and geogrid reinforcements are notdamaged or displaced beyond the acceptable tolerances during deposition, spreading,

leveling and compaction of the fill.

6. Fill materials should not be dumped or heaped high close to the blocks. Fill should bedumped near the rear or middle of the reinforced soil zone and bladed towards the front

face.

7. Fill should be placed and compacted in lifts with appropriate thickness consistent withvertical spacing of reinforcement, nature of fill materials, type of compaction equipment and

the required relative compaction. The uniform loose lift thickness of reinforced fill should

not exceed 300 mm.

8. Care must be taken to ensure that the compacted surface the drainage media / fill near theback of the block is uniform, level and not below the top of the block (it is advisable to keep

the surface of fill slightly above the top of the block). This is to avoid sagging of the geogrid

at / near the connection with the block, when the next lift of fill is placed, resulting in

additional loads in the geogrid not considered in design.

9. Placement of each lift should start only after carrying out the necessary tests on the


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previous finished layer and after obtaining the permission from the Engineer.

1.4.8.4 Compaction Equipment1. Fill within a distance of 300 mm from the back face of the modular blocks (typically the

drainage media, except may be below the GL / service rod FRL) may be compacted with

hand-held tampers or vibratory plate compactors.

2. Fill beyond 0.3 m and within 1.5 from the back face of the blocks may be compacted with awalk-behind vibratory roller with a mass not exceeding 1500 Kg or a vibratory plate

compactor with a mass not exceeding 1000 Kg.

3. Beyond a distance of 1.5 m from the back of the blocks, the fill may be compacted withsmooth drum vibratory rollers of mass 8 to 10 MT.

1.4.8.5 Relative CompactionThe minimum required relative compaction of the fill shall be 95 % of Maximum Dry Density

determined in the laboratory. However, within a distance of 1.5 m from the facing a relative

compaction of 90 to 95 % is acceptable.

For pavement sub grades, the minimum required relative compaction shall be 97.5 % of

Maximum Dry Density determined in the laboratory.

1.4.9 Installing The Geogrid Reinforcement:-

a) Care should be taken to ensure that geogrid reinforcement of the required type and lengthare installed at the levels shown in the drawings. The length of reinforcement (LR) marked

on the longitudinal section drawings is the clear length from the back face of the blocks.

Hence cutting length of geogrid should be LR + 0.25 m (to ensure embedment betweenblocks).

b) Before laying the geogrid, the top surface of blocks shall be cleaned to remove any fillmaterials, aggregates etc. with wire brush or stiff broom. The surface of the drainage layer /

fill adjacent to the blocks must be inspected to ensure that it is compacted properly with a

uniform flat finish level with the top of the blocks or slightly above the top of the blocks.

c) Geogrids should be laid with its principal strength direction (machine / longitudinaldirection) perpendicular to the wall face. The front end of the geogrids should be positioned


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on the top surface of the modular blocks, such that it will be just behind the bottom front

edge of the subsequent course of blocks to ensure that geogrids will not be visible from

outside (figure 2). Geogrids should be placed without any folds or wrinkles. Adjacent

geogrids should be butt-jointed (no overlap is required), ensuring that there is no gap

between them.

d) Place the next course of blocks over the geogrid in a running bond configuration, taking carenot to displace the geogrids. The upper course of blocks should be adjusted so that the

tongue and groove joints engage, ensuring the required setback.

e) Pull the back end of the geogrid to removed any slackness (at the same time do not applyexcessive force which may misalign the blocks) and pin it in position with removable U-pins

or stakes.

f) Before commencing placement of fill above the geogrid, ensure the following:i) Geogrid is free from any damageii) There are no gaps between the adjacent sheets of geogridsiii) There are no pits, depressions, excessive undulations or sharp objects below the geogrid.

Take particular care to avoid any such defects immediately behind the facing blocks.

iv) The geogrid has been stretched to remove any folds / wrinkles / excessive slacknessand pinned / secured properly to avoid displacement during placement, spreading,

leveling and compaction of fill.


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1.4.10Placement of Drainage Bay:-

1. Install the drainage system, simultaneously with the placing and compaction of fill. Thedrainage fill should be brought up at the same rate as reinforced and retained fill, taking

care to prevent any mixing with other soils.

2. Drainage layer should be compacted by hand-held tampers or vibratory plate compactors.3. Particular care should be taken to ensure that for any course, the finished surface of the

drainage bay is slightly above the level of the top surface of the blocks. This is to ensure that

the geogrid reinforcement will not tend to sag at the connection with the blocks, when the

subsequent lift of drainage layer / fill is placed.

4. Install drainage outlet pipes as shown on the drawings.

1.4.11Casting of Coping Beam:-

After the block erection is complete, provide cast in-situ coping to achieve the required

longitudinal profile of the wall.

1.4.12Quality Control:-

Tests on Reinforced and Retained Fill

The tests to be conducted on reinforced fill and their frequency are as follows:

S.No Test / Property Method Frequency

1 Sieve analysis IS 2720 Part 41 test per 1500 cum

of fill

2 Liquid limit and Plastic limit IS 2720 Part 51 test per 1500 cum

of fill

3Maximum dry density and

IS 2720 Part 81 test per 1500 cum

optimum moisture content of fill

4 Angle of shearing resistance IS 2720 Part 131 test per 3000 cum

of fill


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Tests on Embankment Fill

The tests to be conducted on embankment fill and their frequency are as follows:

S.No Test / Property Method Frequency

1 Sieve analysis IS 2720 Part 41 test per 1500 cum

of fill

2 Liquid limit and Plastic limit IS 2720 Part 51 test per 1500 cum

of fill

3Maximum dry density and

IS 2720 Part 81 test per 1500 cum

optimum moisture content of fill


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Various Materials used and their specifications

Plan


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Longitudinal Section


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Plan of Precast Fascia Block

Elevation


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Isometric View

3D View of arranged blocks


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Connection between Blocks and Geogrid

Documents

Reinforced Earth Wall