LSU Historical Dissertations and Theses

1997

Dissertation

Degree Name

Doctor of Philosophy (PhD)

G. Wije Wathugala

Abstract

Geosynthetics are widely used as reinforcements in various earth structures. Current design methods are based on some simplified assumptions and are primarily modified versions of limit equilibrium methods used in design of the unreinforced earth structures. All of these design methods are conservative and result in uneconomical design. The best method for verifying the design assumptions and studying the stress-deformation behavior of geosynthetic reinforced earth structures is by constructing a series of large scale test walls with adequate instrumentation and collecting data from them. But the cost involved in such a scheme precludes undertaking this kind of study. Thus Numerical simulation provides an alternative and cost effective means for such a study. In the present research, a finite element model has been established for the numerical simulation of geosynthetic reinforced earth structures. The $HiSS\ \delta\sb1$ model has been implemented in the finite element method for modelling granular backfill. A new calibration technique has been developed based on genetic algorithms (GA). The new technique allows one to calibrate a constitutive model even when all the test data needed for calibration are not available. An elasto-plastic constitutive model based on the disturbed state concept (DSC) has been developed and implemented in the finite element method to model soil/geosynthetic interfaces. The interface model has been validated by simulating the large scale pull-out tests performed at the Louisiana Transportation Research Center (LTRC), and the finite element model of the geosynthetic reinforced wall has been validated with the observed behavior of two large scale test walls which were constructed and tested at the University of Colorado at Denver and the Royal Military College of Canada. The finite element simulation is able to predict the measured behavior of these walls well and the results of the simulation show some discrepancies and conservativeness in the assumptions made in the current design methods. The present finite element model can be used for parametric study and for formulating a realistic design method.

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