Study On Passive Pile Based On Transparent Soil Model Test And Numerical Simulation

With the high speed development of our country's construction,many high-rise buildings,bridges and harbors emerge constantly,high-speed railways and highways,development of urban subway construction,large-scale backfill in costal areas become intensively,and the phenomenon of pile bears load transferred by the soil passively occurs frequently in many engineering practices.At present the research subject of pile-soil interaction is pile body but the attention to the soil around the pile is limited,and due to soil property the degree of visualization in model test is low,besides the complete and accurate deformation field cannot be obtained.In this study,the author applied the combination of transparent soil and PIV technology to passive pile model test,selfdesigned a 3D dimensional displacement measurement system includes optical table,model box system,laser and CCD cameral et al.,and the system was used to measure displacement field of the soil around pile in a non-intrusive way.Furthermore the finite element software ABAQUS was applied to simulate the model test and important parameter sensitive analyze.At first,by reading a large number of literature,summarizing previous experience and combining characteristics of this model test,the author designed a model box system suitable for passive pile transparent soil model test.An appropriate material and method for transparent soil was chose to guarantee the speckle field of transparent soil that can be seen clearly.The software PIVview2 C was used to process image that obtained from passive pile transparent soil model test,and the results indicate that: in the case of single pile the burial depth of pile has significant influence on pile-soil interaction,the relative displacement of soil around pile increases with the increase of pile burial depth.In the case of two-pile,the pile spacing has apparent effect on soil arching,with the decrease of pile spacing the displacement contour of soil between piles becomes more close to the shape of arch.The displacement field of soil around the pile shows this kind of change rule because the soil produces horizontal displacement under the action of external load,but in this process the existence of pile limits the part of soil displacement result in non-uniform relative displacement,and due to the cohesive force and friction between soil grains the soil arching produces gradually.The three-dimensional finite element model based on transparent soil model was established by ABAQUS software,the consistency of result about the displacement contour between model test and numerical analysis verifies the feasibility and accuracy of passive pile transparent soil model test.After that in the numerical simulation of single pile,the influence of soil lateral displacement pattern and pile diameter on soil displacement field around soil was researched.The result shows that the rectangular displacement shape has greatest effect on pile-soil interaction and parabola shape secondly,triangle shape minimum,and the larger the pile diameter the more obvious the pile-soil interaction.For the two-pile and double-row piles numerical simulation,the impact of pile spacing,soil cohesion and lay-out mode of double-row piles on soil arching was analyzed from the perspective of soil stress.The distribution curve of soil horizontal stress along the X-axis and Y-axis was plotted,furthermore the pile-soil load sharing ration was calculated.The changing law of curves shows that with the decrease of pile spacing and the increase of soil cohesion,the soil arching becomes more obvious and the pile-soil interaction becomes more remarkable;for double-row piles the arrangement of three in front and two behind is slightly obviously than the arrangement of two in front and three behind in terms of pile-soil interaction.This research has reference value for revealing the pile-soil interaction law and mechanism of passive pile,in addition can provide scientific basis for the optimization design of passive pile and other practical engineering problems.