identification of parameters using plaxis and backanalysis ... meeting... · identification of...

IDENTIFICATION OF PARAMETERS USING PLAXIS AND BACKANALYSIS PROCEDURE

UPC group, Barcelona

Underground M3 – Barcelona, 11th December 2009

OUTLINE

1. INTRODUCTION

1a Backanalysis1a. Backanalysis1b. Plaxis

2. REMINDER

3 OBJECTIVE3. OBJECTIVE

4 WORK CARRIED OUT4. WORK CARRIED OUT

5. FUTURE WORK

INTRODUCTION ‐ Backanalysis

DIRECT PROBLEM: Geometry + set of parameters predict displacements, stresses, strains, etc.

INVERSE PROBLEM:Geometry + Measurements estimate parameters and assess the integrity of theparameters and assess the integrity of the materials involved

Backanalysis from field data can be performed in a systematic mannerBackanalysis from field data can be performed in a systematic manner

Gioda & Sakurai (1987), Gens et al (1988, 1996), Ledesma et al (1996,1997)…

b k l l f f ld lSystematic backanalysis as a tool for integrity assessment of old tunnels

INTRODUCTION ‐ Backanalysis

Compare measured and computed variables:

2

*m

i iF x x 1i

Computed with a model, i.e. F.E. Model

Depend on “p” parameters:Measurements ( )Mx p

Mi i f F i h h b d hMinimum of F gives the parameters that better reproduce the measurements with that model

Mathematical problem: minimising FMathematical problem: minimising F

If 1 or 2 parameters, simple inspection. If more parameters, algorithms

( th ti l diffi lti li it i i i t )(mathematical difficulties: nonlinearity, minimum unique or not…)

OUTLINE

1. INTRODUCTION


2. REMINDER



5. FUTURE WORK

INTRODUCTION ‐ Plaxis

Plaxis is a geotechnical commercial program initially developed in TechnicalUniversity of Delft It is becoming very popular among the geotechnicalUniversity of Delft. It is becoming very popular among the geotechnicalcommunity.

It is a code based on the Finite Element Method.It is a code based on the Finite Element Method.

It includes three blocks:

Input The block where you introduce the geometry and the parametervalues.

Calculation The block where you define the calculation properties andmakes the calculations

Output The block where you can view the results.

It is Windows based and it works ONLINE

INTRODUCTION ‐ PlaxisInput

INTRODUCTION ‐ PlaxisCalculation

INTRODUCTION ‐ PlaxisOutput

OUTLINE

1. INTRODUCTION


2. REMINDER



5. FUTURE WORK

REMINDERP M ti 2008Prague Meeting ‐ 2008Identification of lining joint stiffness and London Clay Ko by backanalysis.

Tunnel of the Jubilee Line between Baker Street and Bond Street (L=1542 m and φ≈4 m)Tunnel of the Jubilee Line between Baker Street and Bond Street (L=1542 m and φ≈4 m) in London Underground, built in the seventies using a shield.

REMINDERP M ti 2008Prague Meeting ‐ 2008

• Gravel and coarse material (Layer A)• London Clay (Layer B)• Red clays “Lambeth Group” (Layer C)• Carbonate sand “Lambeth Group”(Layer D)• Chalk (Layer E)• Chalk (Layer E)

EF G/H I

JE

F G/HI

C

D K

L

C

D

EJ

K

A

B M

N B

CL

M

A N


Best-fit Perfect Circle

Circularity Survey Data

Deformation exaggerated x 100Estimated Centre

“in situ” measurements Plaxis “measurements”


X* : Measured eccentricity.X : Eccentricity values obtained from the direct analysis using PlaxisXPlaxis : Eccentricity values obtained from the direct analysis using Plaxis.d : Segment thickness (used to make the error dimensionless).Cr : Joint stiffness for rotation.

REMINEDP M ti 2008Prague Meeting ‐ 2008

4 Ko8 Joint Stiffness

32 possible solutions = open input Plaxis 32 times to changethe parameter values + open calculation Plaxis 32 times torecalculate the model + open output Plaxis 32 times to view8 Joint Stiffness recalculate the model + open output Plaxis 32 times to viewthe solutions.

32 possible solutions were analysed “by hand”32 possible solutions were analysed “by hand”. BUT………….imagine

4 Ko8 Joint Stiffness5 E50 24000 ibl l ti5010 Eeod5 Eur3 Cohesion

24000 possible solutions

W d l h i i !We need to analyze that in an automatic manner !

OUTLINE

1. INTRODUCTION


2. REMINDER



5. FUTURE WORK

OBJECTIVE

Build an “OFFLINE” tool capable of:Changing the parameter values.

Running Plaxis calculations.

E i h l d i h bj i f iExtracting the results and computing the objective function

2

*m

i iF x x + ++ 1

i ii

THE TOOL (Plaxis whit Fortran)

OUTLINE

1. INTRODUCTION


2. REMINDER



5. FUTURE WORK

WORK CARRIED OUT

Agreement with Plaxis to know the internal organization of the software. Visit to Plaxis (Delft) to know if it was possible to do it.

Q estions to Pla isQuestions to Plaxis:

How can I change the parameters without opening Plaxis?

Parameters values FILE

Where are the values?

WORK CARRIED OUTQ ti t Pl i

How can I run automatically Plaxis?With a batch file we can open the calculation program, but we can’t run the calculation

Questions to Plaxis:

p p g ,program with our new parameters.

How is this key represented in the Plaxis files?

WORK CARRIED OUTQ ti t Pl i

How can I extract the results to evaluate my objective functionQuestions to Plaxis:

Are the result files here?

WORK CARRIED OUT

Aft th t i t ti ith Pl i C t t d t b ildAfter that interaction with Plaxis Company, we started to build“The Tool”.

The Tool was built with Fortran.

We have built already THE TOOL_1.0 that only can change theh i l (It th t t ) d ki icohesion values (It was the prototype) and we are working in

THE TOOL_2.0 that it could change a lot of parameters like: Eref,E50ref E d

ref E ref ν φ c’ ψ Y f c’i Ko Ri t and EiE50 , Eeod , Eur , ν, φ, c , ψ, Yref, c incr, Ko, Rinter and Eincr.

WORK CARRIED OUT

How THE TOOL works. It looks for the parameter values fileIt looks for the parameter values file.

It translates the parameter values file from machine language to text language.g g

WORK CARRIED OUTHow THE TOOL works.

It reads the parameter values file and asks to the user what parametersIt reads the parameter values file and asks to the user what parameters are being changed.

It changes the parameter values file with the new values and translates g pit from text language to machine language.

It calculates all possible solutions.p

It extracts the results and calculates the objective function

Everything performed in an automatic manner

OUTLINE

1. INTRODUCTION


2. REMINDER



5. FUTURE WORK

FUTURE WORK

Work on the development of “The Tool”

In parallel an algorithm to minimize the objective function shouldIn parallel, an algorithm to minimize the objective function should be developed. A combination of genetic algorithms + gradient methods has been considered appropriatepp p

Synthetic cases could be analyzed by mid 2010

+ Installation of sensors in Barcelona Metro

(Official end of the project by 30th June 2010)

Application to real cases: end 2010, … 2011

identification of parameters using plaxis and backanalysis ... meeting... · identification of...

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