Several issues in three-dimensional numerical analysis of slopes reinforced with anti-slide piles

Several key issues in three-dimensional numerical analysis of slopes reinforced with anti-slide piles are systematically studied.A large finite element program considering the interaction of pile-soil-slope is used to achieve the factor of safety(FOS) and the critical slip surface(CSS) for the slopes stabilized by a row of piles,some key factors such as computational model scale,pile location,ratio of pile spacing to pile diameter,pile length and contact mode at the pile bottom are adequately discussed combined with a typical slope example.In addition,bending moments,shear force,horizontal displacement and lateral earth pressure for the stabilizing piles under four pile top constraints are also analyzed in detail.Some important conclusions are drawn according to the research results to guide the engineering practice and amend the design code for stabilizing piles,which include:(1) The FOS for a slope with reinforcing piles is the same under five computation model scales such as half pile,single pile,double of half piles,double piles,single pile and double of half piles.However,the computational cost under half pile condition is the least one.(2) The maximum FOS can be obtained when the piles are inserted in the middle of the slope,rather than the top or the toe of the slope.The relation between the FOS and pile location in a slope shows a parabolic curve.(3) The FOS for a slope with reinforcing piles will decrease with the increasing the ratio of pile spacing to pile diameter,the optimal ratio is S/D =2-6,because soil arching is formed between the piles.(4) The optimum stabilizing depth for the pile in homogeneous soils can be chosen to be 2/5 pile length.