考虑位移影响的有限土体基坑土压力研究

Soil Pressure of Finite Soil Mass FoundationConsidering Displacement Effect

经典土压力理论假定墙后为半无限土体,对于有限土体情况下的土压力问题不再适用。利用研制的土压力试验模型装置进行不同开挖深度的室内模型试验,采用微型土压力盒测量从静止到开挖稳定后的非极限状态的土压力分布变化,并在此基础上与理论计算方法进行对比,进一步分析有限土体情况下位移对土压力的影响规律。研究结果表明:有限土体情况下不考虑位移时,基坑有限土体侧桩后土压力曲线变化规律与半无限土体侧一致(处于非极限状态),桩后整体土压力比半无限土体侧大;有限土体侧桩体水平位移曲线变化特性与半无限土体相吻合,但桩体整体水平位移量比半无限土体侧小,其中有限土体侧最大位移量比半无限土体侧小45.16%;桩后有限土体土压力随着桩体水平位移增大而减小,这满足非极限状态下的土压力计算模型;考虑位移时,基坑两侧的土压力随着支护桩位移增大而减小,且有限土体侧的减小幅度小于半无限土体侧。

Since the classical earth pressure theory assumes that the soil behind the wall is a semi-infinite soil,it is no longer applicable to the problem of earth pressure in the case of finite soil.Using the developed earth pressure test model device,a set of indoor model tests with different excavation depths were carried out,and the earth pressure distribution change from a static state to a stable non-limiting state after excavation was measured by using a miniature earth pressure box.On this basis,it was compared with the theoretical calculation method to further analyze the influence of displacement on the earth pressure in the case of limited soil.The research results show that when the displacement is not considered in the case of finite soil,the change law of the soil pressure curve behind the side pile of the finite soil of the foundation pit is consistent with that of the semi-infinite soil side in a non-limiting state,and the overall earth pressure behind the pile is larger than that of the semi-infinite soil.the variation characteristics of the horizontal displacement curve of the finite soil side are consistent with those of the semi-infinite soil,but the overall horizontal displacement of the pile is smaller than that of the semi-infinite soil,and the maximum displacement of the finite soil side is 45.16%smaller than that of the semi-infinite soil.The soil pressure of the finite soil behind the pile decreases with the increase of the horizontal displacement of the pile,which satisfies the calculation model of the earth pressure under the non-limit state.When the displacement considered,the earth pressure on both sides of the foundation pit decreases with the increase degee of the displacement of the supporting piles,and the decrease of the finite soil side is smaller than that of the semi-infinite soil side.