桩基穿越欠固结土层设计事故分析及处理

Analysis on accident of pile foundation passing through under-consolidated soil and treatment

某框架结构办公楼在未完全竣工时,即出现地坪下陷、桩基不均匀沉降以及上部结构损伤等现象,不得以在后期进行纠偏加固处理。结合该工程事故案例,对其桩基设计过程中相关岩土参数取值开展了调查、研究、分析,论证了负摩阻力在欠固结土桩基设计中对桩基承载力和沉降影响的重要性。同时,还针对在实际工程设计中如何正确理解规范条文展开讨论。指出在用静载试验确定穿越欠固结土桩基的Ra值时,结果偏不安全,需作适当调整。相关结论可为今后的桩基设计提供更安全、更经济的参考。

The ground subsidence,uneven settlement of pile foundation and upper structural damage were discovered in a frame building in the construction period,so the reinforcement treatment must be carried out. Aiming at this accident case,we carried out a series of investigations and studies on its geomechanical parameter selection in the pile foundation design,so the importance of negative surface friction to the bearing capacity and settlement of pile foundation was made clear. Furthermore,we discussed how to correctly understand the provisions of the specification in practical engineering design. It is not enough to determine the Ra value of pile foundation passing through under- consolidated soil by static test,so the adjustment is necessary. The results provide a reference for the safer and more economical pile foundation design in the future.