NUMERICAL SIMULATION OF PILE-SOIL INTERACTION PROCESSES IN LAYERED SOIL USING PARTICLE FLOW SIMULATION

The interaction between pile and layered soil was investigated based on a project with pile foundations in Shanghai. The interaction between pile and soil was simulated using parallel-bonded model considering the layered distribution of the soils. The microscopic mechanical properties were characterized with seven parameters, including ball-ball contact modulus, ball stiffness ratio, frictional coefficient of the particles, parallel-bond modulus, parallel-bond stiffness ratio, parallel-bond normal strength, parallel-bond shear strength. The bond strength and stiffness ratio were determined based on the cohesion and compression modulus of the soils. The microscopic parameters were calibrated based on the in-situ load-displacement curve. The two-dimensional particle flow code in simulating the interaction between pile and soil was developed. The interaction between pile and soil particles and movement features of particles were thereafter explored. It shows that the moving features were different in different soil layers; the displacements of clay particles were greater than those of the sand ones; the contact force between pile and soil particles were different in different soil layers, and the contact forces in sand were greater because of its greater friction coefficient and stiffness; the force chain propagated mainly along the normal direction. These results are referable in investigating the load transfer mechanism of piles in layered soil under external loads.