Research On Passive Pile Effect In Soft Soil Foundation Under Heaped Load

With the rapid development of economy in China,a lot of infrastructure construction is needed everywhere,especially in coastal cities,such as cross sea bridge,highway along the river and other engineering construction in full swing,but the soil here is relatively soft.Therefore,in the process of construction in the silt land area,the development of various landfills and construction will often cause the lateral displacement of the underlying soil layer.This kind of horizontal displacement makes the lateral earth pressure acting on the adjacent pile foundation extremely large,which causes the horizontal displacement and deformation of the adjacent pile foundation,and causes the instability or damage of the upper structure,leading to engineering accidents.There is no clear design guide for the influence of the lateral displacement of this kind of soft soil on the passive pile.In this paper,the indoor model test and finite element method are used comprehensively to study the passive pile effect and horizontal bearing capacity of the pile foundation in the soft soil layer.Considering the distance between the pile and the load,the degree of soft soil compaction and the size of the pile load,study the deformation of the pile foundation,the soil pressure around the pile and the pile-soil interaction mechanism.In this paper,firstly,the soft soil of a site in Bao'an District of Shenzhen is used,a series of indoor model tests are carried out to study the passive pile effect under different influence factors in the process of filling.Secondly,the numerical model is established and compared with the test results.The propagation law of the lateral earth pressure is analyzed by the validated finite element method,and the parameter analysis is carried out.Finally,the influence law of the pile displacement caused by the pile load distance,the pile load size and the soft soil compression modulus is obtained by the calculation analysis,and the empirical formula of the maximum pile displacement is given.The test and numerical results show that the force and displacement of pile body increase significantly with the increase of pile side load or the decrease of pile load distance,while the displacement of pile body increases slightly with the decrease of compression modulus of soft soil,but the influence is small.The influence of pile loading on pile is mainly the lateral displacement of soil.The maximum negative bending moment of pile body occurs in soft soil layer,and the maximum positive bending moment occurs in the interface of soft and hard soil layer.For the lateral earth pressure around the pile,the lateral earth pressure of soft soil mainly occurs in the middle and upper part of the soft soil layer,the closer to the pile load,the greater the earth pressure,while at the bottom of the soft soil layer,the pile load has little effect on the lateral earth pressure.For passive piles,the p-y curve method in the code will overestimate the soil pressure on the pile side and underestimate the displacement of the pile body.Compared with the case with piles,the attenuation of earth pressure without piles is slow,and there will be no sudden drop of earth pressure behind piles due to the blocking of piles.When the pile position exists,compared with the case without piles,the earth pressure before piles will be increased and the earth pressure after piles will be reduced due to the blocking of piles near piles.