螺杆桩承载机理及承载力计算方法研究

Research on Bearing Mechanism and Bearing Capacity Calculation Method of Screw Pile

依托昌景黄高铁螺杆桩地基处理工程,通过数值模拟,对比研究直桩和螺杆桩竖向承载特性,分析极限荷载下不同螺距螺杆桩桩周土体破坏模式,并对螺杆桩单桩承载力计算方法进行探讨。结果表明:与同直径直桩相比,螺杆桩极限承载力提高约30%;螺距的大小对桩周土体的破坏形式有所影响,螺距较小时,桩周土体形成圆柱形剪切破坏面,螺距较大时,桩周土体沿梨形滑移面破坏;当螺距过小或过大时,螺杆桩极限承载力均有所减小。实际工程中螺距取值满足螺纹段桩周土体发生圆柱形剪切破坏的条件,基于圆柱形剪切破坏形式,提出了螺杆桩单桩承载力计算方法。

Relying on the screw pile foundation treatment project of Nanchang—Jingdezhen—Huangshan highspeed railway, through numerical simulation, the vertical bearing characteristics of straight pile and screw pile are compared, and the failure mode of the soil around the pile with different pitch under ultimate load is analyzed, and the calculation method of single pile bearing capacity is analyzed. The results show that: the ultimate bearing capacity of screw pile is about 30 % higher than that of straight pile with the same diameter;the failure mode of the soil around the pile is affected by the size of the screw pitch. When the screw pitch is small, the soil around the pile will form a cylindrical shear failure surface;when the screw pitch is large, the soil around the pile will break along the pear shaped slip surface;when the screw pitch is too small or too large, the ultimate bearing capacity of the screw pile will decrease. In practical engineering, the value of the pitch satisfies the condition of cylindrical shear failure of the soil around the pile. Based on the cylindrical shear failure form, a calculation method of single pile bearing capacity is proposed.