Seismic Response Analysis Of Rigid-Sub-Rigid Pile Composite Foundation Under Saturated--Unsaturated Sand Site

As an advanced foundation treatment technology,rigid-sub-rigid pile composite foundation has a good application prospect.However,at present,the research on rigid-sub-rigid pile composite foundation at home and abroad is mainly limited to the static aspects such as vertical bearing capacity and settlement,while the research on dynamic aspects,especially the seismic dynamic response,is relatively less.In this paper,based on the shaking table model test of rigid-sub-rigid pile composite foundation under saturated--unsaturated sand site,considering the pile-soil interaction in rigid-sub-rigid pile composite foundation,the seismic dynamic response of rigid sub rigid composite foundation is studied in depth.The main research contents are as follows:(1)The dynamic response of saturated sand and unsaturated soil is analyzed theoretically,and the dynamic response equations and solution methods are given;(2)In order to effectively improve the boundary conditions in the test process,and realize the bidirectional vibration and three-dimensional vibration,this paper selects the circular laminated shear model box,and according to the similarity relationship,makes the Large scale shaking table test model of 4×4 rigid-sub-rigid pile composite foundation under dry sand site conditions and saturated sand site conditions;(3)According to the shaking table test results of the rigid-sub-rigid pile composite foundation under the condition of dry sand site,the acceleration amplification coefficient,displacement,Fourier spectrum and strain of the composite foundation with different excitation peak value,different seismic wave types,one-way input,two-way input and three-way input are analyzed with the change of burial depth,and the rigid-sub-rigid pile under the condition of dry sand site is obtained The law of seismic response of pile composite foundation;(4)Based on the shaking table test results of the composite foundation with rigid-sub-rigid piles under the site conditions of saturated sand,the variation of acceleration amplification coefficient,displacement,Fourier spectrum and strain with the depth of embedment in different excitation peaks,different seismic wave types,one-way input,two-way input and three-way input are analyzed,and the site conditions of saturated sand are obtained The variation law of seismic response of composite foundation with lower rigid-sub-rigid piles.In addition,the influence of sand liquefaction on the composite foundation of rigid-sub-rigid piles is analyzed;(5)The shaking table tests under two site conditions are compared and the dynamic response characteristics are analyzed.In this paper,the dynamic response characteristics of rigid-sub-rigid pile composite foundation under two different site conditions are discussed;(6)Based on the results of shaking table test,a three-dimensional finite element analysis model of rigid-sub-rigid pile composite foundation in saturated sand site condition is established.The acceleration time history,Fourier spectrum,acceleration amplification coefficient and strain test and simulation values of the pile are compared,and the correctness of the numerical model is verified.