基坑工程中有限土体土压力的计算问题因支护结构的位移控制比较严格,需要考虑非极限状态土压力理论,而以往的研究大多是关于砂性有限土体在非极限状态下土压力理论的探讨,且相关计算方法仍然是基于传统的朗肯土压力理论,事实上对于不满足半无限边界条件的有限土体,朗肯土压力理论是不适用的。对于不满足半无限边界条件的黏性土有限土体,在已有研究的基础上,对墙后梯形滑动楔形土体进行分块处理;采用水平薄层法分别对其进行分析,并考虑黏性土体内摩擦角和黏聚力发挥值以及墙土之间外摩擦角和黏聚力发挥值与位移的关系,构建在非极限状态下黏性土有限土体土压力强度的微分方程;再通过推导得出黏性土有限土体在非极限状态下的土压力强度计算公式。与实际算例实测结果对比分析表明:自填土表面至基坑一定深度范围内,计算值较实测值偏大;而在一定深度以下范围内,计算值与朗肯土压力计算值差异明显,而与实测值的符合程度较好。综合来看,所提出方法是合理可行的,可供相关设计参考。

Due to strict control for the displacement of retaining structure in excavation engineering, the theory of soil pressure in non-limit state should be considered in the calculation of soil pressure of limited soils. However, most previous studies were confined to the earth pressure of sandy limited soil under non-limit state, and the calculation methods are based on traditional Rankine’s earth pressure theory which is not applicable in semi-infinite boundary condition. In view of this, for cohesive limited soils which do not meet the semi-infinite boundary conditions, we divided the trapezoidal sliding wedge soil into blocks, and established the differential equation of earth pressure strength of cohesive limited soil at non-limit state according to the curves of mobilized angles of internal friction and external friction and mobilized cohesion vs. displacement angle, respectively. Furthermore, we derived the calculating formula for earth pressure of cohesive limited soils at non-limit state. Calculated values are larger than measured values in the range from soil surface to a certain depth of the pit; while beyond that depth, the calculated values conformed well with measured values but differed greatly from Rankine’s value. In general, the calculation method presented in this paper is reasonable and feasible.