瞬态入渗下圆台形基坑主动土压力的滑移线解答

Slip line solutions of active earth pressure for a circular platform foundation pit under transient infiltrations

摘要

为描述瞬态入渗下圆台形基坑主动土压力沿深度的分布规律，基于非饱和土的广义有效应力强度公式和瞬态入渗下的基质吸力，建立了圆台形基坑主动土压力的滑移线方程，继而采用差分迭代法获得了瞬态入渗下非饱和土圆台形基坑主动土压力的滑移线解答，最后对所得滑移线解答开展准确性验证和影响因素分析。研究结果表明：所得滑移线解答相比现有解能合理考虑瞬态入渗（时间、入渗率、吸应力非线性分布）、土体类别（砂土、粉土、黏土）、基坑模型参数（墙壁倾角、墙土摩擦角）和环向应力系数对基坑主动土压力的综合影响，其准确性在特定条件下得到文献饱和土圆台形基坑主动土压力滑移线解答（吸应力为0时）、瞬态入渗下平面挡墙主动土压力极限平衡解答（基坑半径趋于无穷时）的退化验证；时间、入渗率对黏土基坑主动土压力大小及分布的影响最明显，对粉土基坑主动土压力的影响次之，而对砂土基坑主动土压力的影响可忽略不计，这是由不同土体的吸应力非线性分布造成的；基坑主动土压力随着墙壁倾角、墙土摩擦角、环向应力系数的增加均显著减小，且沿深度的分布及变化与土体类别密切相关。

Abstract

In order to characterize the distribution law of active earth pressure with depth for a circular platform foundation pit under transient infiltrations，this study derived the slip line equation for the active earth pressure of circular platform foundation pits.The derivation was based on the strength equation of generalized effective stress for unsaturated soils and matric suction under transient infiltration conditions.Subsequently，the differential iterative method was adopted to obtain the slip line solution of active earth pressure for circular platform foundation pits under transient infiltrations.Last，the accuracy of the obtained slip line solution was verified，and an influencing factor analysis was conducted.The results indicate that the obtained slip line solution，compared with the existing solutions，can reasonably account for comprehensive influences of transient infiltration（time，infiltration ratio，nonlinear profiles of suction stress），soil types（sand，silt，clay），foundation pit model parameters（wall dip angle，wall-soil friction angle），and the circumferential stress coefficient on the active earth pressure of foundation pits.The accuracy of the obtained slip line solution of active earth pressure under specific reduced conditions is demonstrated by comparing it with the slip line solution of circular platform foundation pits in saturated soils（when suction stress is zero），and the limit equilibrium solution of plane retaining walls under transient infiltrations（when the radius of foundation pit tends to infinity）reported in the literature.The influence of time and infiltration ratio on the value and distribution of active earth pressure is most pronounced for foundation pits in clay，followed by foundation pits in silt.However，it is negligible for foundation pits in sand，which is caused by nonlinear profiles of suction stress for different soils.The active earth pressure of foundation pits decreases significantly with the increase of wall dip angle，wall-soil friction angle and circumferential stress coefficient，while its distribution and change with depth are closely related to soil types.

关键词

瞬态入渗 / 圆台形基坑 / 主动土压力 / 滑移线法 / 环向应力系数

Key words

transient infiltration / circular platform foundation pit / active earth pressure / the slip line method / the circumferential stress coefficient

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基金资助

国家自然科学基金资助项目(41202191)