عنوان مقاله [English]
This paper reflects the role of different constitutive models on the deformations induced by tunneling in urban area. These constitutive models were applied in finite element analysis of tunnel-induced subsidence for case study of Amirkabir Tunnel in Tehran. The results of this paper indicate that numerical simulation of tunneling induced settlement with hardening soil small strain stiffness model is much more accurate than other constitutive models.
Accurate prediction of tunneling induced settlement is one of the most important challenges encountered in urban underground projects. Generally, such predictions are usually obtained by application of numerical simulation, where the accuracy of the results depends on several factors. The constitutive models play an indicative role on the accuracy of numerical simulation of tunneling induced settlement. This issue was studied by comparing the effect of different constitutive models on the development of ground deformations around tunnel and also the tunneling induced settlement for a case study.
Methodology and Approaches
Finite element analysis of tunneling induced deformations using PLAXIS software was performed for three different elasto-plastic constitutive models including Mohr-Coulomb, hardening soil, and small strain hardening. The input data of numerical simulation were captured from different in-suite and laboratory tests on the host ground of Amirkabir tunnel as case study. Tunnel construction was modeled based on the as-built condition of excavation stages of T4 section of Amirkabir tunnel. Finally, numerical results were compared and verified with monitoring results and field measurements.
Results and Conclusions
Results show that the Mohr-Coulomb model shows lower prediction of vertical displacements comparing to two other implemented models. Furthermore the Mohr-Coulomb model shows an unrealistic uplift of tunnel floor after all of the excavation stages. Results illustrated that using hardening soil models, with sophisticated features including non-linearity pre-failure and high stiffness under small strain, considerably improves the prediction of displacements. It is observed that using hardening soil small strain stiffness model the accuracy of predictions comparing to the field measurements increase obviously. A fully comparison between the results from Mohr-Couloumb and Hardening Soil cases yields some important differences which are presented in this paper.