Study On Wall Stability And Vertical Bearing Capacity Of Bored Piles Near The Front Edge Of Yangtze River Delta

In actual engineering,the vertical bearing capacity of bored piles is related to the safety of the superstructure.Due to different soil material properties and groundwater level conditions,the vertical bearing capacity of bored piles will also change significantly.In order to study the influence of soil properties and groundwater conditions on the vertical bearing performance of bored piles,a single-pile indoor vertical bearing model test was carried out,aiming at the stability of the hole wall of the pile body and the vertical bearing of the defective pile body The performance was analyzed by finite element.The main research work of this article is as follows:(1)Three kinds of soil quality and three kinds of water content conditions were considered,a sliding test device for the interface between the pile body and the soil layer was developed,and an interface sliding test study between the single pile and the soil layer was carried out.The influence of different soil materials,water content and other factors on the pile side friction resistance is analyzed.The research results show that the trend of side friction resistance-slip curve of piles under different soil qualities is similar.When the slip value is small,the lateral friction resistance increases as the slip value increases;when the slip value is large,the lateral friction resistance tends to be stable,and when the soil layer is at the optimal moisture content,the lateral friction resistance exerts more performance it is good.(2)An experimental device capable of considering the variation of the water level inside the soil was developed,and the vertical bearing performance of the pile body under three types of soil was tested in the natural state and the groundwater infiltration state.The research results show that groundwater reduces the effective stress of the soil body,and weakens the friction and slip characteristics between the pile body and the soil layer,so that the vertical bearing capacity of the pile body decreases greatly;at the same time,the three types of soil are fine sand The vertical bearing capacity of the pile body under the floor is maximized.(3)Based on the finite element software ABAQUS,the lateral deformation performance analysis of the pile hole under various size conditions was carried out.The results show that the location of the soil with large lateral deformation near the front edge of the Yangtze River Delta mostly appears between 13m-20m;when the hole diameter is constant,the deeper the pile hole,the lateral soil layer deformation is also larger;when the hole depth is constant,the hole diameter The greater the lateral deformation of the soil layer,it can provide a reference for preventing hole wall collapse and choosing a reasonable pile size during construction in this area.(4)The finite element software ABAQUS was used to analyze the lateral deformation performance of the pile hole under various mud specific gravity conditions.The results show that the larger the specific gravity of the mud,the smaller the lateral deformation of the hole wall,but when the specific gravity of the mud continues to increase,the lateral deformation of the hole wall is closer.(5)Through the finite element software ABAQUS,the vertical bearing performance of the pile body under various defect conditions is simulated.The research results show that the greater the thickness of the pile side mud and the pile end sediment,the vertical bearing capacity of the pile body will decrease,and the loss rate of the vertical ultimate bearing performance will increase;The bearing effect is small,but the greater the degree of necking,the greater the change in the axial force of the pile body at the necking position.The paper has 68 drawings,29 tables,and 108 references.