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Liquefaction is one of the consequences of earthquake in soil layers comprised of saturated loose sands. Various aspects of liquefaction have been investigated using different methods of field, laboratory, and numerical studies. Numerical simulation of liquefaction constitutes a major part of these researches. Application of a proper constitutive law in the numerical analysis is crucial for modeling the complicated undrained behavior of saturated sands during dynamic loading. Simplicity of formulation, limited number of parameters, and good performance are the main features of a proper constitutive law. In this study, an Endochronicbased model for simulating liquefaction of sand is implemented into the finite element program, PISA. Coupled dynamic field equations of Biot's theory with u-p formulation are used to determine pore fluid and soil skeleton responses. Generalized Newmark method is employed for integration in time. The developed code is capable of predicting the magnitude of the generated pore water pressure, coupled with advanced constitutive laws such as critical state twosurface plasticity as well as simple models such as MohrCoulomb. Simulating cyclic simple shear and centrifuge tests using Endochronic model showed favorable performance of this model for predicting the variation of pore water pressure in saturated soil layers subjected to earthquake excitations.

In this study, the effects of some geotechnical parameters on the surface settlement curves due to mechanized tunneling and the corresponding risk on surface buildings are investigated through numerical analysis. The advanced constitutive law of Plastic Hardening is utilized to accurately reflect the Soil behavior in unloading. Using the surface settlement curves obtained from numerical analysis, the risk category of surface buildings are calculated and the effectiveness of each parameter on the risk level is investigated. The results show that the cohesion and friction angle do not have a remarkable effect on surface settlement and the corresponding risk. However, the amount of overburden and the soil elastic modulus considerably affect the surface settlement and the risk level subjected to the surface buildings. Recognizing the role of each parameter makes it possible to predict the potential risk on surface buildings and to optimize the approaches for mitigating these risks.

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