Research On The Soil Compaction Effect And Bearing Capacity Of Pipe Pile Construction In Soft Soil Area

With the development of the economy,the capacity and service level of existing roads are far from meeting people's growing travel needs,and more and more highways are included in the planning of reconstruction and expansion.Reconstruction and expansion project often passes through the soft soil area with insufficient geological bearing capacity,prestressed pipe piles are widely used in the reinforcement treatment of soft soil foundations due to the advantages of simple process and convenient construction,but some problems are gradually exposed in the application,and there will be obvious squeezing effects during the construction of pipe piles,which is manifested as when the pile sinks,the soil on the pile side is squeezed by the lateral displacement and vertical uplift,and then the soil within a certain range of the pile is squeezed to make the adjacent pile body tilt and affect the quality of the pile.The research on the extrusion effect is mostly limited to single pile penetration,and there is less research on the working state of pile group,and it has little guiding significance for actual engineering.Therefore,this paper uses on-site monitoring,indoor testing and numerical simulation to conduct in-depth analysis of the evolution mechanism of the extrusion effect,the deformation characteristics of pile soil,bearing characteristics,parameters and process optimization in the process of pile sinking,and the main research contents are as follows:(1)Research on the formation and evolution mechanism of pipe pile extrusion effectThe visual model experiment is used to reveal the development and evolution mechanism of the extrusion effect,and through the study of the distribution law of the displacement field of the soil body,the soil peri-pile is divided into three regions.The influence range of soil deformation in the horizontal and depth directions was determined,and the effect of the extrusion effect on the adjacent pile body was based on rotation and translation,and the effect of changing the pile spacing and the order of sinking piles was analyzed,and the corresponding optimization measures were obtained.(2)Research on the parameters and process optimization of extrusion effectThe particle flow procedure was used to conduct a more in-depth study of the pile sinking process,and the macro-fine response difference between sand and soft clay to the pile sinking was analyzed.The control variables such as soil compactness,pile sinking rate,and change of pile sinking method were analyzed,and the difference between macroscopic performance such as soil displacement and microscopic response such as porosity was studied,and technical measures to control soil compaction and reduce pile sinking rate were determined.On the basis of considering common processes,the disposal effect of pre-introduction hole and anti-extrusion groove measures on weakening the extrusion effect is analyzed.(3)Research on bearing performance of piles based on extrusion effectThe bearing capacity of the pile was studied using flac procedure,and the spatial distribution of displacement field,stress field and plastic zone under load was analyzed.The difference in the bearing characteristics of piles in the offset state is studied,and it is pointed out that the offset state has little influence on the compression deformation of the pile,but has a greater impact on the settlement,horizontal displacement and soil pressure on the pile side.By establishing the composite foundation model of pile group reinforcement,the transmission mechanism of pile soil displacement and stress under the partial state of pile group is revealed.(4)Field experimental study on soil compaction effectThrough field experiments,the changes of deep soil displacement and pore water pressure in the process of piling are dynamically monitored,and the changes of horizontal displacement of deep soil with direction,distance and penetration are analyzed,and the spatiotemporal variation characteristics of ultra-static pore water pressure are obtained,and the changes of deep soil with depth,time,dissipation rate,penetration degree and pile sinking rate are analyzed.The research in this thesis further analyzes the formation and evolution mechanism of the extrusion effect,improves its design theory,optimizes its construction process,and studies the bearing characteristics of the pile on the basis of considering the extrusion effect,which has important engineering significance.