防汛抢险螺旋桩改进设计及沉桩试验

Improved design and pile-driven experiment analysis of anti-flood spiral pile

为进一步提高防汛抢险螺旋桩的便携性并降低能耗,根据桩土作用原理及力学平衡理论对沉桩阻力进行分析,提出了相应的桩体结构改进措施,即适当减小空心圆柱体外径并保持锥体底面外径不变和适当减小螺旋叶的长度。通过改型前后桩体的现场沉桩试验,得到了沉桩扭矩对比曲线。试验结果表明,两种措施可使防汛抢险螺旋桩的最大沉桩扭矩大幅度下降(分别下降了39.3%和16.5%);防汛抢险螺旋桩的沉桩扭矩存在极值,且改型后的桩体提高了沉桩时桩体截面强度的安全系数;改型后的桩体受到横向载荷后横向位移会有所偏大,但能满足实际使用要求。

Based on the pile-soil interaction principle and mechanical equilibrium theory, we analyzed the pile-driven resistance and proposed two relevant measures to improve pile-body structure in order to improve portability and reduce energy consumption of anti-flood spiral pile. The first measure is to properly reduce outside diameter of hollow cylinder with invariable bottom outside diameter of cone, and the second measure is to properly reduce length of spiral blades. Thus, we obtained the contrast pile-driven torque curves by driving original pile and modified pile. The curves show that the maximum pile-driven torque is greatly reduced by 39.3% and 16.5%, respectively, due to the two measures. It also shows that the pile-driven torque of anti-flood spiral pile has an extreme value, and the modified pile increased the safety coefficient of pile section intensity when pile-driven. Moreover, the modified pile still meets the actual requirements although its lateral displacement would be larger than the original pile for lateral load.