沉井接高过程中砂桩复合地基固结承载特性

Consolidation Characteristics and Bearing Behavior of Sand Pile Composite Foundation in Caisson Heightening

为分析沉井接高过程中固结对复合地基承载力的影响,以某大型陆上沉井基础的砂桩复合地基工程为背景,探讨了沉井接高过程中砂桩复合地基的固结特性,分析了加荷历时和砂桩置换率等因素的影响.基于桩土面积比法和桩土应力比法推导了考虑固结影响的砂桩复合地基极限承载力公式,并与复合地基实测承载力进行对比.结果表明:两种分析方法得到的复合地基承载力时程曲线较为接近,且初始承载力均小于复合地基实测承载力,而固结完成后的承载力比复合地基天然强度分别提高了68%和80%.该方法考虑了沉井接高过程中地基固结对其承载力的影响,避免了因低估地基的实际承载力而导致沉井滞沉问题,可为考虑固结影响的复合地基极限承载力计算和制定合理的沉井施工方案提供参考.

To study the influence of consolidation on the bearing capacity of the composite foundation in the process of caisson heightening,the consolidation characteristics of the sand pile composite foundation in the process of caisson heightening are discussed based on the sand pile composite foundation engineering of a large-scale onshore caisson foundation.The influence of loading duration and replacement rate of the sand pile are analyzed.Based on the area ratio method of pile-soil and the pile-soil stress ratio method,the formula of the ultimate bearing capacity of the sand pile composite foundation considering the consolidation effect is derived,which is compared with the measured value of the ultimate bearing capacity of the foundation.The results show that the time history curves of the bearing capacity of the composite foundation based on the two methods are close,and the initial bearing capacity is less than the measured value of bearing capacity,while the bearing capacity after consolidation is 68%and 80%higher than the natural strength of the composite foundation.This method considers the influence of consolidation on the bearing capacity of the foundation in the process of caisson heightening.It can avoid the problem of stagnant sinking of open caisson as it underestimates the actual bearing capacity of the foundation,and provides suggestions for calculation of ultimate bearing capacity of the composite foundation considering the influence of consolidation and formulating the reasonable construction scheme of open caisson.