基于太沙基极限平衡理论的螺纹桩承载力计算

Calculation of Bearing Capacity of Screw Pile Based on Terzaghi Limit Equilibrium Theory

基于太沙基极限平衡理论,对螺纹桩极限承载力进行理论推导,提出螺纹桩两种破坏模式下临界螺距的确定方法和螺纹桩极限承载力计算方法,分析了不同参数对螺纹桩承载力的贡献。研究结果表明:螺纹桩破坏模式由临界螺距H_(cr)决定,螺距大于临界螺距时为螺牙独立破坏模式,小于临界螺距时为圆柱剪切形破坏模式;螺纹桩螺牙改变了桩体的承载方式,对比同外径圆桩承载力约提高40%,在达到极限荷载时,螺牙提供的承载力约为总承载力的85%;影响螺纹桩螺牙承载力的主要土体指标为黏聚力c、摩擦角φ以及埋深,而滑动区土体自重因素对螺牙承载力的贡献并不明显;当考虑抗剪强度提供的竖向力时,螺纹桩的极限承载力最大提高20%左右。

Based on the Terzaghi limit equilibrium theory,the ultimate bearing capacity of screw pile is deduced theoretically.The methods to determine the critical pitch and calculate the ultimate bearing capacity of screw pile under two failure modes are proposed.The contribution of different parameters to the bearing capacity of screw pile is analyzed.The results show that:the failure mode of screw pile is determined by the critical screw pitch H_(cr).When the pitch is larger than the critical pitch,it is the independent screw failure mode;when the pitch is smaller than the critical pitch,it is the cylindrical shear failure mode.Compared with the bearing capacity of the circular pile with the same outer diameter,the existence of screw changed the bearing mode of the screw pile,and the bearing capacity of screw pile is increased about 40%.When the ultimate loading is reached,the bearing capacity provided by screw is about 85%of the final bearing capacity.The main soil indexes that affect the bearing capacity of screw pile are cohesion force c,friction angleφ,and buried depth,while the contribution of dead weight of sliding zone to the bearing capacity of screw pile is not obvious.When the vertical force provided by shear strength is taken into account,the maximum ultimate bearing capacity of the screw pile can be increased by about 20%.