Abstract: The self-boring in-situ shear pressuremeter (SBISP) has little disturbance to the surrounding soil. It can simultaneously determine the deformation and strength parameter of easily disturbed soil at depth and has an extensive application prospect in the determination of soil parameters accurately. However, the deformation response of surrounding soil under multilevel loading process in SBISP test has seldom been studied up to present because of the limitations of the analytical tools and research level. At the same time, the determination of the deformation parameter of the soil is closely related to its deformation mechanism. Based on this, the SBISP model test under different consolidation pressures is simulated by particle flow code in three dimensions (PFC3D). The results of numerical experiments show that the displacements of particles in central area increases with the shear stress imposed stepwise; and the direction of displacement vector shows a clearly preferred direction. The shape of displacement vectors in influence area is a reverse cone under the fifth grade shear stress. Additionally, with the increase of the consolidation pressure, the influence area of the numerical sample diminishes gradually. The motion trails of particles are step-like lines; the steps are becoming gentler as the distances from particle to the probe rob center increasing; and the vertical displacements of particles descend in a negative exponential form. The magnitude of shear stress depends on the frictional coefficient of the probe; the shear stress-shear displacement curve is no longer changes when it reaches a certain value. This study is of great enlightened significance in the further research of the relation between deformation process and deformation modulus of soil under multilevel loading process in the SBISP test, which lies in the influence area.

Key words: self-boring in-situ shear pressuremeter test, particle flow, deformation response, different consolidation pressures, motion trails