膨胀土附加应力场对深基坑土压力的影响

Earth pressure of deep foundation pit effected by additional stress field of expansive soil

采用由假定温度应力场模拟含水率变化引起的膨胀土附加应力场,给出相对热膨胀系数β的求解方法和不同含水率对应的温度变化。以合肥地铁某膨胀土深基坑为例,考虑最大月降雨量降雨和基坑周边土体含水率变化至饱和状态2种情况,研究围护结构在平移模式(T)和绕墙底转动模式(RB)下的土压力分布规律,提出考虑膨胀土附加应力场的土压力修正计算方法。当围护结构位移小于0.3%H时(H为基坑深度),降雨对土压力有影响,最大增量在地表处,为0.44P_e,影响深度约为4 m且线性递减。土体整体饱和时,土压力的增量是定值,为0.57Pe。

Additional stress field of expansive soil caused by moisture change was simulated by virtual temperature stress field, in which solution of relative thermal expansion coefficient fl was proposed and equation of temperature change and moisture change was gained. A case study of some deep foundation pit in expansive soil strata in Hefei was done. The distribution of earth pressure of different displacement of translation mode （T） and rotating about base mode （RB） was proved up and modification of calculation method of earth pressure of deep foundation pit was proposed, in which additional stress field caused by maximum monthly rainfall and moisture of the whole ground changed to saturated was considered. The results show that distribution of earth pressure will be affected by rainfall when displacement of envelope is less than 0.3%H（H represents the depth of pit）, the largest impact position occurs at ground surface and decreased linearly. Increment of earth pressure is 0.44Pe and its influence depth is about 4 m. Increment of earth pressure is a fixed value when ground moisture is saturated, and the value is 0.57Pc.