Abstract
Deep excavation in natural structured clay causes disturbance to the surrounding soil, which damages the soil structure and results in soil strength reduction. This study investigates excavation-induced disturbance in natural clay based on a case of subway station excavation. A series of piezocone tests was performed adjacent to the diaphragm wall before and after excavation to determine the disturbance degree based on cone tip resistance. The stress and deformation variations in soil were also obtained via numerical simulations, and the mechanisms of excavation-induced disturbance were proposed based on the numerical simulation results. The results showed that excavation caused a decrease in the cone tip resistance, and the disturbance degree of soil determined by cone tip resistance ranged from 0% to 50%. At identical locations, the disturbance degree of soil increased with excavation depth. The main reason for excavation disturbance is the increase in shear stress. Therefore, shear strain can serve as an indicator of the degree of disturbance, and the relationship between disturbance degree and shear strain can be expressed by a power function. The degree of soil disturbance is affected not only by the magnitude of the diaphragm wall horizontal displacement but also by its deformation distribution pattern.