seismic subsidence of soft subgrade with considering principal stress rotation

Under cyclic loads such as earthquake, the complex stress path involving continuous principal stress rotation existed in the soil. it is a common but easily neglected phenomenon. the previous research on soft subgrade considering principal stress rotation caused by an earthquake is not enough. it is urgent to carry out research to reveal the seismic subsidence of soft soil considering the effect of principal stress rotation. based on the results of soft soil by gds hollow cylinder apparatus, the effect of softening behavior on soft soil’s modulus is simulated by the strength reduction method. a umat (user material) subroutine is programmed and embedded into the finite element software to establish the soft soil model under earthquake. the effect on seismic subsidence of soft soil under different breadth depth ratio or soft soil’s thickness is studied. the results show that the seismic subsidence of soft soil reaches the maximum in 18–25 s, and the seismic subsidence is about 290% higher than that in 0–8 s; the effect is more obvious in the soft soil model when the breadth depth ratio is small. the seismic subsidence of soft soil increases by 72% when the breadth depth ratio s is 1.25; considering the effect of principal stress rotation, the vertical deformation of the model’s edge is about 800% higher than vertical deformation of the middle of the model’s surface; the influence on seismic subsidence of soft soil isn’t significant when the thickness of soft soil layer exceeds 8 m. the law of the deformation of soft soil seismic subsidence can be provided by the result considering the effect of principal stress rotation, which can be regarded as a theoretical basis for anti-earthquake design soft soil region. © 2022, iran university of science and technology.