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在考虑开挖引起土体回弹和土体强度特性、应力状态变化的基础上,提出了开挖条件下非均质地基中竖向受荷单桩非线性计算方法,并与已有试验结果对比,证明了简化方法的正确性,并对开挖前、后单桩的竖向承载特性的变化以及开挖后土体回弹对基桩受力和变形的影响进行研究分析。研究表明,常规试桩法和套管试桩法高估了基桩竖向极限承载力和桩顶刚度,采用常规试桩和套管试桩法得到的承载力作为设计值偏于不安全;开挖卸荷引起桩周土体回弹使得桩身出现拉力,开挖深度较大时桩身中、下部的配筋应充分考虑由于开挖引起的沿桩身的拉力,防止开挖过程中基桩被拉断;桩周土体的卸荷回弹将会引起桩顶刚度的明显降低。
Based on the consideration of the soil rebound and soil strength characteristics and the change of stress state caused by the excavation, the nonlinear calculation method of the pile subjected to vertical load in the heterogeneous foundation under excavation is proposed. Compared with the existing test results The correctness of the simplified method is proved. The change of the vertical bearing characteristics of single pile before and after excavation and the influence of soil rebound on the stress and deformation of the pile after excavation are studied. The results show that the conventional test pile method and the casing test pile method overestimate the vertical ultimate bearing capacity and the pile top rigidity of the pile. The bearing capacity obtained by the conventional test pile and the casing test pile method is unsafe as the design value. Excavation and unloading caused by the soil around the pile body rebound so that the pile tension occurs, excavation depth larger, the lower part of the pile reinforcement should be fully due to excavation caused by the tension along the pile to prevent excavation process The foundation pile is broken off; the unloading rebound of the soil around the pile will cause the pile top stiffness to be obviously reduced.