Study On Calculation Method Of Horizontal Loaded Pile In Loess Site Based On Strain Wedge Method

At present,the research on the horizontal bearing behavior of pile foundation in loess site is not sufficient,especially the theoretical calculation method of pile group foundation under horizontal load is still lacking.The strain wedge method is a theoretical calculation method for laterally loaded piles that can better consider the pile-soil interaction and the nonlinear constitutive relationship of soil.Therefore,this paper comprehensively adopts the research methods of theoretical analysis,numerical simulation and model test to study the calculation method of strain wedge and the influencing factors of pile group effect of horizontal loaded piles in loess site.The main research contents and conclusions are as follows:（1）Based on the strain wedge theory,an improved calculation method of strain wedge for horizontal loaded single pile in loess site is proposed,and the influence of tensile strength of loess and friction resistance on both sides of wedge on calculation is analyzed.The reduction coefficient f_m is introduced to reduce the foundation reaction modulus E_s,and the calculation method of strain wedge of horizontally loaded pile group is proposed.The evolution process of pile group effect in soil plane is analyzed by numerical simulation.The results show that the evolution process of pile group effect in pile group foundation under horizontal load is mainly the emergence and expansion of stress coincidence zone between co-row and co-column adjacent piles and the increasing stress level of coincidence zone.（2）Through the horizontal loading model test of single-row piles,the stress and deformation characteristics of each pile in single-row piles and the influence of edge effect on the deformation and internal force of piles are studied,and the rationality of the strain wedge calculation method of pile group is verified.The results show that:the bearing capacity of each pile in the same row of piles is different.Under the same horizontal load,the displacement of the side pile top is smaller than that of the middle pile and the secondary side pile.The more shallow buried depth is,the more significant edge effect is.The edge effect gradually weakens with the increase of the buried depth of the soil,and the edge effect will not appear beyond a certain depth.（3）Based on the strain wedge calculation method of pile group proposed in this paper,the influence of pile number,pile diameter,pile length,pile spacing and soil friction angle on the horizontal bearing characteristics of pile group is analyzed by the strain wedge calculation method.The results show that:the pile number,pile spacing,pile length and pile diameter have great influence on the horizontal bearing capacity and pile group effect coefficient of pile group,while the internal friction angle of soil has little influence.The critical pile spacing SP₁ and SP₂are 8D and 2D respectively,and the critical pile length is 20D.For the pile group foundation,the load sharing ratio of the front row pile is the largest.The pile spacing and pile diameter have a great influence on the load sharing of each row pile in the pile group foundation.The number of piles,the length of piles and the internal friction angle of soil have little influence on the load sharing of each row pile in the pile group foundation.