Study On Pile-soil Interaction With Contact Element

According to the case of Yichang-Wanzhou project, through the contact finiteelement simulation method, contact finite element model between the pile and soft rockhas been established by large-scale finite element software ANSYS.Through the studyon the vertical bearing properties of large diameter rock-socketed piles in the soft rockfoundation,main conclusions as follows:(1)Considering the effect of the horizontal width of the rock, the vertical depth ofthe rock at the end of the pile and the rock-socketed depth of the pile,it shows that thefinite element model is the most reasonable when the horizontal width of the rock isabout10times of pile diameter,the vertical depth of the rock at the end of the pile is3times of the pile length and the rock-socketed depth of the pile is4times of pilediameter.When external loads are small,the phenomenon of slip bewteen the pile androck can be simulated more accurately,pulling in Goodman unit without thickness,andthe results are more reasonable.(2)The value of the relevant parameters of the contact unit has a greater impact onthe force of the contact surface and the settlement of the pile-rock system.Amongthem,the impact of the normal and tangential stiffness is greatest.The greater normal andtangential stiffness,the smaller settlement of the top of the pile,the smaller penetrationvalue on contact surface. Analyzing the specific values of the normal and tangentialstiffness on contact surface by the constant method, the tangential stiffness of thecontact unit is more appropriate when it is50～100times of modulus of elasticity ofthe soft rock.(3) Studying the interaction bewteen the pile and rock by the plane model,theaxisymmetric model and the three-dimendional solid model,the simulation using theaxisymmetric model is more reaonable generally in the pile-rock system with single pilesince its efficiency is better than the three-dimendional solid model,and its accuracy isbetter than the plane model.