Www.oasys-software.com Xdisp Webinar Oasys. Zeena Farook Geotechnical Application Engineer Today’s Presenter

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XdispWebinar

Oasys


Zeena Farook

Geotechnical Application Engineer

Today’s Presenter


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Who is Oasys?

• Software house of Arup

• Formed in 1976 to develop software for in-house and external use

• Most developers are engineers who have moved to programming

• In recent years have added marketing, sales, and development staff worldwide

• Network of Agents


Structural

Geotechnical

CAD

Document Management

Sustainability

Crowd simulation


Oasys Customers


Objectives

•Appreciate Xdisp theory and its use in industry

•Set up a simple tunnel and excavation analysis

•Set up a simple Building Damage and Utility Damage Assessment

•Demonstrate the Graphical Input feature


Xdisp – An introductionSoil Displacements due to Excavations


Xdisp

• Calculates ground movement due to excavations

• Typical use:

• Tunnel excavations in soft ground (i.e. nothard rock tunnelling)

• Shafts

• Retained cuts (e.g. deep basements)

• Mined excavations

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Xdisp analysis methods

1. Tunnel induced ground movements

2. Mining induced ground movements

3. Excavation induced ground movements


• Equations for the curves are generated from the normal or Gaussian distribution

• Normal distribution relationship shows a close match to tunnelling induced case study movements at ground and sub-surface levels.

• Can be difficult to achieve similar results using FE (Addenbrooke & Potts St James’s Park FE analysis described in CIRIA 2001)

1. Tunnel induced ground movements1.1 Generalised form of movement


• Relationship is ‘empirically’ based, not analytically based (i.e. one that uses soil properties such as strength, stiffness etc.)

• Parameters of importance are:

• Volume Loss (m³/ m run)

• Trough width parameter (k)

=> The complete three dimensional behaviour of the ground due to tunnelling can be defined

1. Tunnel induced ground movements1.1 Generalised form of movement


Definition:

Ratio of the additional volume of excavated ground over the theoretical volume of the tunnel

Volume loss depends on many factors, including:

- Tunnelling method (TBM type or SCL)

- Ground and groundwater conditions

- Flexibility of lining etc.

Many authors have provided guidance on volume loss based upon case studies.

Empirical approach considering C/D and P/D proposed by Macklin (1999)

1. Tunnel induced ground movements1.2 Volume Loss


Trough Width Parameter

Sand(typically k = 0.3)

Clay (typically k = 0.5)

1. Tunnel induced ground movements1.2 Trough Width Parameter


Other authors have proposed relationships of i to k for different conditions at surface:• O’Reilly & New (1982), surface displacements• Boscardin, surface displacements• New & O’Reilly (1991), surface displacements, multi layered deposits

Can use the above relationships, however, many practitioners use i = k / zo

for surface displacements. This is generally adequate and simpler (this is‘user defined k’ in XDISP)

Either of the following is commonly used for sub-surface displacements:• Mair et al (1993) – only really for tunnelling in clay (because k = 0.5 atsurface)• New & Bowers (1994)

1. Tunnel induced ground movements1.2 Trough Width Parameter


• Method proposed by Ren et al (1987)

• Defines surface displacements

2. Mining induced ground movements


• Surface displacement curves from CIRIA C580

• Can input curves from empirical data

3. Excavation induced ground movements3.1 Surface Displacement Curves


• Initially derived from surface curve where displacement=0 at base

but sub surface curves more realistic

• Derived from empirical data or FE analysis of excavation

in similar soil

• Detailed method included intraining materials

3. Excavation induced ground movements3.2 Sub surface Displacement Curves


• Previous (no corner stiffening)

• New (corner stiffening*)

* Fuentes R. and Devriendt M. (2010). Ground movements around corners of excavations - An empirical calculation method. Journal of Geotechnical and Geoenvironmental Engineering. Volume 136, Issue 10, pp. 1414-1424.

3. Excavation induced ground movements3.3 Corner Stiffening


Xdisp input• Tunnel/mine type• Displacement points for calculation (line, grid, point)

• Displacement points for plotting (line, grid, point)

• Tunnel• Wall installation & excavation

• Mine• Buildings


Xdisp Inputs - Preferences and defaults

• Tabbing past a table cell with a default will fill the cell with the default value

• Defaults can also be edited – click in the grey cell at the top


Xdisp Inputs - Table tips

• = in a cell copies the cell above

• == in a cell copies the rest of the line above

• In long tables, ctrl-G lets you type in the line to go to

• Right-click brings up a whole list of options – modify probably the most useful


Xdisp output

• Ground movement• Displacements

• Building Damage Assessment

• Utility Damage Assessment


Case StudyCopenhagen Metro


Copenhagen Metro – The design brief

• 15.5km metro line with 17 underground stations

• Stations are cut-&-cover structures, retained within a station box of either secant piles or diaphragm walls.

• Geotechnical challenges include the requirement to limit settlements


Copenhagen Metro – The settlement assessment• Oasys XDisp was used to calculate the settlements

at the ground surface caused by the construction of the tunnels.


Copenhagen Metro – The settlement assessment• Screening - identification of any structure where the

predicted settlement from bored tunnels is more than 5 mm or the predicted slope is more than 1/500.

• XDisp showed how specific structures performed in relation to the damage categories using building damage interaction charts

• This list was used to identify buildings where building protection may be required, allowing a means of assessing the contractor’s proposed works during tender evaluation.


Xdisp RunthroughTunnel and Excavation Analysis

1. Set up a tunnel and excavation problemi. Input displacement lines and gridsii. Input tunnels and excavationsiii. Input sub surface displacement curves

2. Run analysis

3. Navigate tabular and graphical outputsi. Export tabular resultsii. Plot graphsiii. Manipulate 3D Graphics



Xdisp – Further analysis

1. Building Damage Assessments

2. Utility Damage Assessments

3. Other recent developments


Categories of damage (order of increasing importance):

• Visual appearance or aesthetics• Serviceability or function• Stability

Commonly used system which expands on above is that proposed by Burland et al (1977)

Increasing foundation movement

1. Building Damage Assessments1.1 How is damage defined?


Category of damage

Category of damage

Description of typical damage Approx crack width* (mm)

Limiting tensile strain (%)

0 Negligible Hairline crack < 0.1 < 0.05

1 Very slight Fine cracks that can be easily treated during normal decoration

1 0.05 – 0.075

2 Slight Cracks easily filled. Redecorating may be required

5 0.075 – 0.15

3 Moderate Cracks require some opening up and can be patched by a mason

5 – 15 0.15 – 0.3

4 Severe Extensive repair work involving breaking and replacing sections of walls

15 – 25 > 0.3

5 Very severe

Requires a major repair job involving partial or complete rebuilding

> 25

1. Building Damage Assessments1.1 How is damage defined


Three stages defined:Stage 1 – Preliminary assessment

Settlement contours

Stage 2 – Second stage assessmentBuilding Damage Assessments

Stage 3 – Detailed evaluation

Important to note that criteria specified in the above assessment methods rely on the structure being in a ‘reasonable’ state of repair.

1. Building Damage Assessments1.2 Assessment method

Volume 1, Chapter 3 of the book “Building response to tunnelling, case studies from construction of the Jubilee Line Extension project, London


Idealisation of façade or wall of building to behave like a deep elastic beam, see Burland (1995)

Has been shown to be reasonable for brick masonry structures. Examples of use for reinforced concrete structures in (CIRIA JLE, 2001, Vol.2)

1. Building Damage Assessments1.3 Assessment method – Stage 2


Tension TensionCompression

Hogging HoggingSagging

VERTICAL SETTLEMENT (W), HORIZONTAL DISPLACEMENT (V) AND GROUND STRAIN PROFILE

(after Lake, Rankin and Hawley, 1992)


1. Building Damage Assessments1.4 Specific Building Damage Assessments

Export Results with images for each chart and excel files of structures displacement and strain


1. Building Damage Assessments1.5 Generic Building Damage Assessments

Calculates displacements, strains and damage categories for each transect along a polyline

Polyline

Transects


Xdisp RunthroughSpecific Building Damage Assessment


2. Utility Damage Assessments2.1 How is utility damage calculated

Utility displacements and Utility dimensions

strain, pullout, joint rotation

Input

Output

Acceptance criteria can be set to determine if the utility fails

This is summarised in the tabular output and plotted in the graphs


2. Utility Damage Assessments2.2 Generic Utility Damage Assessment

Utilities lie along transects and strain, pullout and joint rotation calculated for each

Polyline

Transects represent utility


Xdisp RunthroughSpecific Utlity Damage Assessment


3. Other recent developments3.1 CAD Imports

DXF Background Import DXF Element Import


3. Other recent developments3.2 Graphical inputs

Data Input via 3D Graphics view


Xdisp RunthroughGraphical Input Feature


Pdisp DevelopmentsXdisp


Pdisp

• Calculates displacements due to the application of a pressure, either loading or unloading

XDisp PDisp


When use Xdisp/Pdisp?

Xdisp


Pdisp

• Calculates displacements due to the application of a pressure, either loading or unloading


Objectives

•Appreciate Xdisp theory and its use in industry

•Set up a simple tunnel and excavation analysis

•Set up a simple Building Damage and Utility Damage Assessment

•Demonstrate the Graphical Input feature


What next?• Support:• Try new Tutorial Manual:

http://www.oasys-software.com/xdisp-tutorials.html • Online training movies• Web site and technical FAQs• mailto:[email protected]• Telephone support at +44 (0) 191 238 7559


Any Questions?

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Www.oasys-software.com Xdisp Webinar Oasys. Zeena Farook Geotechnical Application Engineer Today’s Presenter