雨水入渗条件下地基瞬态极限承载力解析解及其应用  

Analytical solution of transient bearing capacity for unsaturated foundation during rainwater infiltration and its application

作　　者：徐瑞麟 秦卫星[1,2,3] 胡惠仁 刘泽辰 熊轩宇 XU Ruilin;QIN Weixing;HU Huiren;LIU Zechen;XIONG Xuanyu(International Institute of Technology,Changsha University of Science&Technology,Changsha 410114,China;School of Hydraulic and Environmental Engineering,Changsha University of Science&Technology,Changsha 410114,China;Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province,Changsha 410114,China;School of Transportation Engineering,Changsha University of Science&Technology,Changsha 410114,China)

机构地区：[1]长沙理工大学国际工学院,湖南长沙410114 [2]长沙理工大学水利与环境工程学院,湖南长沙410114 [3]水沙科学与水灾害防治湖南省重点实验室,湖南长沙410114 [4]长沙理工大学交通运输工程学院,湖南长沙410114

出　　处：《中南大学学报（自然科学版）》2022年第10期4048-4056,共9页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(51208062,51508039);湖南省自然科学基金资助项目(2022JJ30601);湖南省交通科技计划项目(201140);国家级大学生创新创业训练计划项目(2021105360020)。

摘　　要：为研究雨水入渗作用下非饱和均质地基承载性能演化特性,首先,基于Richards瞬态非饱和渗流方程,引入Gardner土−水特征曲线模型,获得雨水以恒定雨强入渗时均质地基瞬态基质吸力解析解,并利用有限元方法进行考证;其次,基于非饱和土抗剪强度理论,推导基质吸力沿深度非线性分布时地基极限承载力表达式并利用试验数据证明其正确性;最后,以概化非饱和均质地基为研究对象,基于获得的地基瞬态基质吸力解析解和极限承载力表达式,揭示不同雨强和降雨历时情况下地基基质吸力和极限承载力的演化规律。研究结果表明:随着雨水入渗,地基中上部土体基质吸力的大小和分布会发生变化,基质吸力逐渐减小且减小速度呈现先快后慢的特点,沿地基深度呈现明显非线性分布特征;地基极限承载力受基底以下1.5倍基础宽度应力球范围内平均基质吸力的显著影响,其值随着雨水入渗时间或雨强增加而快速降低,最终因应力球范围土体逐渐饱和降低至饱和抗剪强度理论计算的极限承载力;当降雨历相同时时,基底平均基质吸力和地基极限承载力与降雨强度几乎呈线性关系:降雨强度越大,基质吸力减小幅度越大,极限承载力降低越多。建议重点做好基底以下1.5倍基础宽度范围内防渗排水,特别要加强降雨初期地基基质吸力监测,防止雨水入渗引起地基承载性能大幅降低诱发的地基失稳破坏。In order to study the evolution characteristics of bearing capacity for an unsaturated foundation during rainfall infiltration,firstly,the Gardner soil water characteristic model was introduced,a transient analytical solution to matric suction for a homogeneous foundation during rainfall infiltration with constant intensity was derived based on Richards transient unsaturated seepage control equation,which was verified by the finite element simulation results.Then,an expression of ultimate bearing capacity of foundations during rainwater infiltration was obtained on the basis of the shear strength theory for unsaturated soils,considering the influence of nonlinear distribution matric suction,which was validated by experimental results.Finally,the evolution law of matric suction and ultimate bearing capacity for a target unsaturated homogeneous foundation with different rainfall intensity and rainfall time were revealed by the established analytical formula.The results show that the magnitude and distribution of matric suction in the middle-upper part of the foundation change with the rainfall infiltration.The matric suction decreases gradually,and the decrease rate is large at first and low later.The distribution of matric suction in the foundation shows clearly nonlinearity during rainfall infiltration.The average matric suction within the stress bulb zone below the base with 1.5 times the base width has a significant effect on the ultimate bearing capacity of the foundation.The ultimate bearing capacity of unsaturated foundation decreases rapidly with the increase of rainfall time or rainfall intensity,and eventually reaches the calculated value according to the saturated shear strength theory as the soil saturated and the average matric suction disappears.In the same rainfall duration,the average matric suction and the ultimate bearing capacity of the foundation exhibit an almost linear relationship with the rainfall intensity,the greater the rainfall intensity,the higher the reduction rate of the matric suctio

关 键 词：非饱和土 地基极限承载力 基质吸力 解析解 雨水入渗 

分 类 号：TU43[建筑科学—岩土工程]