The influence of the soil constitutive model on the numerical assessment of mechanized tunneling

摘要

There are several soil constitutive models which have been developed based on the different concepts and purposes. Since the soil constitutive models have significant effects on the numerical results, selection of an appropriate model for soil is still a big challenge. In this research, an attempt is made to evaluate the influence of different soil constitutive models on the behavior of the soil subjected to mechanized tunneling procedure. The finite element code PLAXIS~(3D) has been employed for the numerical analysis. The mechanized tunneling process has been numerically simulated by generating a sophisticated three dimensional model including a shallow and a deep tunnel project. The mechanical behavior of the soil has been modeled by the use of three constitutive models from the same family but with different complexity, namely Mohr-Coulomb model (MC), Hardening Soil model (HS) and Hardening Soil model with small strain feature (HS-small) being categorized as simple, intermediate and complex models, respectively. Since, there are several construction stages in the mechanized tunneling process, the stress path existing take place the soil media is complex. To the knowledge of the authors, most of the numerical studies on mechanized tunneling in frictional soils have been conducted by the use of simple MC model which may lead to questionable results due to inappropriate response of this model for complex problems with loading/unloading/reloading cycles. Thereafter, some phenomena such as soil displacement variations and stress paths at the observation points at different locations around the tunnel as well as the ground surface will be presented. Finally, the difference between the results obtained employing the considered constitutive models is discussed and the most relevant constitutive model leading to reliable results is made distinguished.