基坑卸荷回弹变形计算的一种简化分析法

为了有效地计算基坑坑底隆起变形，以基坑坑底所在的平面为基准参考面,把开挖隆起变形看作是坑底土体在上覆土重作用下固结稳定后的卸荷回弹过程,结合土力学中求解地基附加应力的Boussinesq解和“角点法”分析的叠加原理,并考虑残余应力的影响,建立了坑底以下任一深度处土体的卸荷应力和残余应力表达式。同时基于基础沉降计算分层总和法的思路推导了坑底土体回弹量的简化计算公式,从而可用土体的压缩性指标来确定其回弹变形。通过工程实例的对比分析,该简化公式是合理的,且在一定程度上反应了基坑开挖的空间效应。

Simplified analysis method of pit rebound deformation

To calculate the uplift deformation effectively,swith the pit bottom plane as reference surface,the rebound deformation was regarded as an unloading springback process of bottom soil which had been consolidated completely under overlaying soil weight action.Based on the superposition principle of the corner points method and Boussinesq solution,the formulas of the unloading stress and the residual stress at any depth under the pit bottom were presented considering the influence of residual stress.Furthermore, by using the layer rise summation method, the simplified formula was also derived to apply the compression parameters to the calculation of the value of rebound deformation. Finally, the simplified formula was applied to an engineering case. By contrasting the results with field test data, it is shown that the new simplified method is reasonable, and it can reflect the space effect of foundation excavation to some extent.