打桩锤击解析模型及垫层材料参数的优化

Analytical Solution for Pile Hammer Impact and Application of Optimum Design Technique for Determining Cushion Parameters

针对桩锤、桩帽、锤垫、桩垫组成的锤击系统 ,提出一种新的解析模型 .该模型分别用不同的集中质量块表示桩锤、桩帽 ,用一并联的弹簧、阻尼器表示锤垫 ,用一弹簧表示桩垫 ,同时用一阻尼器表示桩 ,建立平衡方程 ,利用拉普拉斯变换推导出锤击力的解析解 .根据锤击力的解析解 ,采用优化设计技术 ,调整参数 ,使桩顶锤击力的解析解与实测桩顶应力波的差值最小 ,得出合理的垫层材料的参数 ,供工程实践参考 .

Analytical solutions of force wave are presented for hammer impact using a model which uses lumped mass for the ram and anvil,a spring and a dashpot for the anvil cushion,and another spring for the cap cushion on the top of a pile.The pile is modeled as a dashpot.The solutions account for the separation of the anvil mass forming the pile cap cushion and the separation of the ram mass forming the anvil cushion.According to the analytical result and in-suit test result,a method was proposed to determine consistent cushion parameters by applying the concept of an optimum design technique.The minimization of differences between the measured and the predicted force waves at the pile head was carried out by optimum design technique.By analyzing analytical examples and in-suit test results,it was found that the adopted optimum design technique gives consistent and convergent results.