Research On Vertical Bearing Characteristics And Group Pile Effect Of Thread Pile

Thread pile is a new kind of variable cross section pile.It has been applied in some engineering practice at home and abroad because of its advantages of large bearing capacity,small settlement and remarkable economic benefit.Due to the existence of peripheral thread,the bearing mechanism of thread pile is very complicated,and the understanding of its vertical bearing characteristics is still insufficient,and relevant research results are few.In order to reveal its bearing characteristics and pile group effect,this paper is based on the existing research results at home and abroad,and nonlinear finite element software Abaqus is used to build numerical model.The main research work and content is as follows:?1?Finite element software Abaqus is carried to analyze the vertical bearing characteristics and influencing factors of thread single pile.The results show that:compared with circular pile with equal section,thread pile is found to have higher bearing capacity and smaller settlement;the bearing capacity of thread pile first increases with S/D,then decreases,and reaches the maximum value within the range of S/D between 0.5 and 2.0;the bearing capacity of thread pile is linearly positively correlated with the width of thread B;there is little relation between the ratio of internal to external thread thickness H_out/H_in and the bearing capacity of the thread pile;the properties of soil around the pile positively affect the bearing capacity of the thread pile,while the properties of soil at the pile end have little influence.?2?Finite element software Abaqus is used to study the vertical bearing characteristics and influencing factors of thread group pile.The results show that:there is negative friction in the part of foundation pile near the bearing platform,and the negative friction effect of the center pile is the largest,followed by the side pile and the angle pile is the smallest;the bearing capacity of group pile increases with S_d,and the maximum increase range is within the range of 4⁵ times the outside diameter of pile.In actual engineering,it is recommended that the pile spacing be controlled at 4⁵ times the pile outer diameter;the bearing capacity of group pile increases linearly with the length L of the pile;the bearing capacity of group pile is linearly positively correlated with the number of pile n,and the linear fit is 0.99;the bearing capacity of group pile decreases with the increase of the thickness t of the bearing platform,and when the t exceeds 0.75 m,the bearing capacity decreases little;the influence of the soil properties around the pile on the bearing capacity of group pile is larger than at the pile end.?3?The theoretical formula method and numerical simulation method are used to calculate the group pile effect coefficient of the thread group pile,and the theoretical calculation value and numerical simulation result are compared and analyzed.The results show that:the existing theoretical formula can be used to calculate the group pile effect coefficient of the thread group pile,but there are certain preconditions in the application.