tunnelling is our business - zsoil · numerics in geotechnics and structures 2010 ......

ArbeitsklausurWagrain, 15./16.04.2010

TUNNELLING IS OUR BUSINESS

Modelling aging shotcrete:parameter identification and application

Matthias Hofmann

Numerics in geotechnics and structures 2010

ALPINE BeMo Tunnelling


• Europe– Austria & alpine region– Switzerland, Germany– Great Britain– Sweden– Eastern Europe

• Asia– India– China– Singapore

• USA• Know-How: worldwide

ABT = Tunnel projects around the world

ALPINE BeMo Tunnelling (ABT)


• ~ 40 000 meters of tunnels/galleries each year• constructor and designer

– specialized in complex 3D-models and analysis of underground structures

Tunnel projects around the world




City Tunnel Leipzig, Lot BLeipzig, Germany




ALPINE & BeMo: ABT = a global tunnel company

ABT = tunnel projects around the world

ABT = in-house tunnel design capability

ABT = know-how as part of tunnel business



Outline

• Motivation• Aging concrete constitutive model• Parameter identification approach• Back calculation of in situ measurements• Conclusions

Modelling aging shotcrete: parameter identification and application


• modelling time dependent behaviour (creep) of „young“/aging shotcrete is important for the design of outer lining in tunnelling

• use of zsoil-aging concrete model for modelling aging shotcrete– many material parameters are required – not all of them have physical meanings difficult to obtain from

measurements

• parameter identification is of special importance• use of aging concrete model for back calculation of in

situ measurements

Motivation


Outline



Aging concrete


Aging concrete

• aging concrete model requires a large number of material parameters

• e.g. 3 Maxwell units, 7 maturity points 24 parameters to identify

• creep behaviour can be modelled • however dependence of strength can not be modelled

viscoplastic model required • is it possible to model time dependent concrete strength

within zsoil?


Outline



Parameter identification approachOptimization problem

• deterministic model relates set of responses x = x(p) and model parameters p

• given measurements x* = [x1* … xm*]T from experiments• objective function for minimization problem

J = (x* - x)T W (x* - x)• optimization using dakota - toolkit


Parameter identification approachDakota toolkit (taken from http://dakota.sandia.gov)


Parameter identification approachDakota – zsoil

dakotaglobal optimization or nonlinearleast square methods

parameterse.g. C1…Cn

simulation - zsoilpython script adapts zsoiltemplate input file

responsemetrics


Parameter identification approachzsoil template file



simulation - zsoilpython script adapts zsoiltemplate input file

responsemetrics


Parameter identification approachzsoil template file

aging concrete material model

load = 1 MPa

• creep test modelled as single element test• load is adjusted within a python script by modifying its load functions


Parameter identification approachDakota – zsoil communication



simulation - zsoilpython script adapts zsoil templateinput file

responsemetrics

• automatic adaption of zsoil input file and evaluation of output-file is important• communication dakota – zsoil via python scripts


Parameter identification approachStructure of python script


Parameter identification approachCalling zsoil

windows pop up for each zsoil-run• sometimes in the background• but sometimes in the foreground• how to avoid pop up windows?


Parameter identification approachBack calculation of creep tests

• creep test data taken from:Zachow (1995): Dimensionierung zweischaliger Tunnel im Fels auf

der Grundlage von in-situ Messungen• used creep tests with constant loads of 5 and 7 MPa for back

calculation• two Maxwell units for aging concrete model were sufficient for this

simple tests• nevertheless 9 parameter have to be identified

parameter identification approach can be used for other constitutive models as well

other parameters (e.g. loads, geometrical parameters, …) could also be identified / optimized


Parameter identification approachBack calculation of creep tests

parameter identification usingone test (5 MPa) withnonlinear least squaresmethod

parmeter identificationusing two tests(5 and 7 MPa)

time [h] time [h]

axia

l stra

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axia

l stra

in[%

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Outline



Back calculation of in situ measurements

• deformations of outer lining are measured every 10 – 20 tunnelmeters

• valuable data for– specification of support for the following excavation steps– back calculation of utilization factor of outer lining– back calculation of loading for design of inner lining

• utilization factor: „stress / strength“, similar to zsoil-stress level– Rokahr, R., and Zachow, R. (1997): A new method for the daily monitoring of the

stress intensity of a sprayed concrete lining; Rock and Soil Engineering, 15(6); 430-434 (in German)

– Hellmich C., and Mang, H. (2005): Shotcrete Elasticity Revisited in the Framework of Continuum Micromechanics: From Submicron to Meter Level

– Tunnel:Monitor®: www.tunnelmonitor.com


Back calculation of in situ measurementsDeformation measurement


Back calculation of in situ measurementsFE model

• cross section modelled with „shell one layer“ – elements, 1m length

• material: aging concrete model• interpolation of measurement data in

time and space– adapting existence functions– adapting load functions of boundary

conditions– done with python scripts

• results (forces, moments) are used for calculation of the utilization factor


Back calculation of in situ measurementsResults: membrane forces and moments

membrane force-XX moment-XX


Back calculation of in situ measurementsResults: save element results in csv-file

• recorded postprocessing macro to extract results in csv-file• python script adapts csv-file name and steps (from *.his file)• tried to run macro from python script (and command line)

• but only Z_POST3D starts, macro is not played and Z_POST3D not closed (same behaviour when running command from command line)

• how to play the record automatically and close Z_POST3D afterwards? (important for automatic calculation of utility factor...)


Back calculation of in situ measurementsResults: utilization factor

• aim is the calculation of the utilization factor for cross sections over time

• ongoing work ...

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100%

7 17 26 42 53 62 74 85 100 114 127 135 148 161 174 187 201 218

tunnelmeter

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example diagram

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Outline



Summary• creep behaviour of shotcrete in early age can be modelled with

zsoil’s aging concrete model• zsoil can be used within an optimization framework by adapting zsoil

input and output files• back calculation of the utilization factor of the outer lining from

measurements can be done with the aging concrete model

Conclusions

Issues• is it possible to model time dependent concrete strength within

zsoil?• windows pop up when calling zsoil from python script • calling Z_POST3D with a macro: how to do?

tunnelling is our business - zsoil · numerics in geotechnics and structures 2010 ......

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