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上海某机械厂有一大直径钢管桩,用于所生产柴油打桩锤出厂前的试用。目前试桩已不满足新生产大吨位柴油打桩锤的试打要求,因此拟增加8根短桩与试桩组成群桩。由于锤击荷载作用下长短组合群桩中荷载的分配及沉降的研究较少,为得到合理的群桩加固型式,采用有限元方法研究锤击荷载作用下群桩的动力承载特性。首先建立单桩有限元模型,分析竖向静荷载作用下钢管桩的沉降,并将模拟结果与现场静荷载试验结果进行对比,验证有限元模型的准确性,再分析锤击荷载作用下单桩的动力响应;其次建立锤击荷载作用下的长短组合群桩有限元模型,分析承台质量、承台埋深、辅桩桩长对群桩桩顶荷载分布及沉降的影响。结果表明锤击荷载作用过程中,角桩、边桩桩顶最大压应力较大,主桩桩顶最大压应力较小;承台埋深越浅,群桩桩顶应力越大,沉降反而越小;承台质量、辅桩桩长对群桩动力特性影响不大。
A Shanghai Machinery Plant has a large diameter steel pipe pile, for the production of diesel pile hammer factory before the trial. At present, the test pile has not satisfied the test-strike requirements of the newly-produced large-tonnage diesel pile hammer, therefore it is proposed to add eight short pile and test pile to form the pile group. Because there is little research on the distribution and settlement of long-short pile groups under the action of hammer loads, the dynamic load-bearing characteristics of the pile groups under the action of the hammer loads are studied by finite element method. First, the finite element model of single pile is established to analyze the settlement of the steel pipe pile under vertical static load. The simulation results are compared with the static load test results to verify the accuracy of the finite element model. Then, the single-pile finite element model Pile dynamic response. Secondly, the finite element model of long and short combined pile group under the action of hammer load is established. The influence of the quality of the pile cap, the depth of cap and the length of auxiliary pile on the load distribution and settlement of group pile top are analyzed. The results show that during the process of hammering load, the maximum compressive stress of pile tip and side stake is larger, and the maximum compressive stress of pile top is smaller. The shallower buried depth of pile cap, the larger the stress of pile group pile top, The bearing capacity and pile length have little effect on the dynamic characteristics of pile group.