Study on Parameters of Modified Mohr–Coulomb Model for Water-rich Soft Soil in Tianjin, China

Abstract

Foundation pit excavation through the soft layer has great technical challenges and potential safety risks, especially in soft soil area. In this study, we use a 3D numerical model of Foundation pit to simulate the excavation process. Based on the simulation, the sensitivity analysis of the three stiffness parameters ({mathrm{E}}_{mathrm{ur}}^{mathrm{ref}},{mathrm{E}}_{50}^{mathrm{ref}} and {mathrm{E}}_{mathrm{oed}}^{mathrm{ref}}) of the Modified Mohr–Coulomb model was carried out by using the Latin hypercube-one factor at a time method. During the simulation, the three stiffness parameters are changed with the perturbation amplitude of (± 20%) and (± 40%). In addition, the sensitivity of three stiffness parameters was calculated by taking the horizontal displacement of diaphragm wall as the observation index. Furthermore, by comparing the results of simulation with the measured data, the stiffness ratio relationship suitable for foundation pit simulation in Tianjin water-rich soft soil area are obtained. Our findings present that {mathrm{E}}_{mathrm{ur}}^{mathrm{ref}} is the parameter that has the largest influence on the uncertainty in the MMC model, while {mathrm{E}}_{mathrm{oed}}^{mathrm{ref}} is the least sensitive to horizontal displacement of diaphragm wall. The proportion rates of {mathrm{E}}_{mathrm{oed}}^{mathrm{ref}}/{mathrm{E}}_{50}^{mathrm{ref}} and {mathrm{E}}_{mathrm{ur}}^{mathrm{ref}}{/mathrm{E}}_{50}^{mathrm{ref}} provide a promising reference for simulating the foundation pit excavation in Tianjin water-rich soft soil area.