Behaviour of an underground metro station for different constitutive models - A study on the influence of Mohr-Coulomb and other advanced constitutive models using PLAXIS 2D for the proposed Chennai Metro Rail Phase 2 project

Abstract

The Phase 2 of the proposed Chennai Metro Rail Project contains underground stations of depths below ground varying from 20m for a 2 level station to 32m for a 4 level station. Diaphragm walls have been chosen for the purpose of earth retention during construction stage and also to be a part of the permanent structure. The centre part of the stations is constructed using top-down methodology and the ends of the station which are used for the purpose of TBM launching and retrieval activities are constructed using either bottom-up or top-down methodologies. The behaviour of the part of the station constructed using top down sequence will be different from the part constructed using bottom up sequence. The current study focusses on the comparison of the influence of the various constitutive models available in the FEM software package PLAXIS 2D such as the basic Mohr-Coulomb model and advanced models such as Hardening soil model and Hardening soil small strain stiffness (HSS) models on the bending moments, shear forces of the diaphragm walls, ground deformations, strut forces etc. This comparative study has been performed on both the top-down and bottom-up sequences and for the different ground conditions along the proposed second phase metro rail alignment in Chennai region of India.