Monotonic and cyclic lateral behavior of semi-rigid pile in cement-improved clay: centrifuge tests and numerical investigation

A systematic study into the behavior of reinforced semi-rigid piles in response to lateral monotonic and cyclic loading in clay was performed with centrifuge modeling tests (100xg). The aim was to investigate the pile-soil interaction mechanism of reinforced semi-rigid piles and to give some generally applicable design advice for reinforcing semi-rigid piles with cement-improved soil. For monotonic loading, the overall load-deflection behavior, profile of bending moment, net soil pressure and pile deflection have been fully studied, in addition to the p-y curves and excess pore pressure response of reinforced and unreinforced piles. It is found that shallow cement-improved soil reinforcement can greatly improve the lateral capacity of piles. In addition, a hyperbolic tangent model was proposed to fit the p-y curves obtained from monotonic tests for reinforced and unreinforced piles. For cyclic loading, it was found that compared with unreinforced piles, reinforced semi-rigid piles reduce the accumulation of pile deflection and the degradation of stiffness. The trends of the cyclic bending moment and cyclic p-y curves are also revealed. A series of supplementary finite element analyses were conducted to study the effects of reinforcement parameters (reinforced width, reinforced depth and strength of cement-improved soil) on lateral pile capacity. It is suggested that shallow reinforcement with a reinforced width of 5D and a reinforced depth above the rotation point of a semi-rigid pile is both economical and practical.