深基坑坑底地基的回弹应力与回弹变形

某长条形地铁车站深基坑,基坑开挖深度15m,通过设置数个分层回弹磁环,测得回弹变形沿坑底深度方向的分布规律;通过固结回弹试验建立回弹模量与卸荷比关系,得到回弹模量沿坑底深度方向的分布规律;结合以上两种成果,并考虑坑底土承受侧向净土压力的伸长作用,得到回弹应力沿深度方向的分布规律:作用在坑底的反向荷载相当于挖去土的自重,因受坑底土有效自重应力的抵消作用,回弹应力沿深度方向呈线性衰减,坑底土的"残余应力"可以认为就是坑底回弹影响范围内的有效自重应力。用上述确定回弹应力的方法计算另一个新近案例的回弹变形,与实测结果比较接近。

Rebound stress and deformation below the bottom of deep excavations

Rebound deformations were measured at different depths below the bottom of a strip excavation of 15m depth.According to the compression-swelling odometer test,the relationship between the rebound modulus and the ratio of unloading at depth below the bottom of the excavation was obtained.Based on the results,with respect to the impact of lateral net pressure,the magnitude of the rebound stress can be determined by the fact that the up-load applied to the bottom of excavation is equivalent to the weight of the removed soil.The rebound stress is reduced by the weight of the soil below the bottom of excavation and decreases linearly with increasing depth.Residual stress is just the effective overburden stress below the bottom of the excavation.In terms of the rebound stress,the rebound deformation can be calculated with high accuracy.