降雨非稳态入渗中堆积体坡包气带气-液耦合过程

Based on in-situ investigation and laboratory tests of the deposits, unsaturated soil theory, and numerical methods, the coupled solid, water and atmosphere, and the effect of air compression on unsteady unsaturated infiltration are researched. Rainfall experiment and physical simulation on typical unsaturated deposits will be executed. Meanwhile, air-liquid coupling law of unsteady unsaturated infiltration associated with landslides is analyzed. On the basis of understanding basic characteristics of two-phase flow characteristics of the unsaturated deposits, boundaries variation of the unsteady seepage caused by rainfall is investigated. Rainfall modeling tests of unsaturated deposits have been carried out under different stress states. According to model test results, the model of solid-liquid-air coupling of the deposits will be established. The model equations will be solved using numerical methods. Then the influence of air-liquid coupling and air compression on the deposits’ unsteady infiltration will be discussed. We will study the intrinsic link between two-phase flow and the landslide in the region of deposits. Associated with engineering, the research results will be applied to seepage evaluation in areas of rainfall-induced landslides and loose deposits. The study will help promote environmental geological hazards in China. And it also has an important theoretical implication for stability analysis of rainfall-induced landslides made of deposits.

基于堆积体的现场调查、室内试验，运用非饱和土力学等理论、采用数值方法对堆积体的降雨入渗的固-水-气耦合以及气体压缩效应进行研究。基于典型非饱和堆积体渗透试验、堆积体降雨的物理模拟等，对降雨作用下非饱和堆积体非稳态流的气-液耦合效应及其与滑坡的内在规律进行研究。在了解典型非饱和堆积体水、气渗透特征的基础上，分析堆积体的二相流特征，探索降雨过程中非稳态渗流的边界变化特征。开展不同应力状态下非饱和堆积体降雨试验。基于模型试验结果，建立降雨作用下非饱和堆积体固-水-气耦合模型，采用数值方法对该模型方程求解，侧重揭示气-液耦合效应以及气体压缩对堆积体非稳态孔隙水压力分布的影响规律，进而研究堆积体中二相流与滑坡的内在联系。结合工程，将研究成果应用于堆积体地区的降雨型滑坡以及松散堆积体坡的渗流评价。该研究将有助于推动我国环境地质灾害学的发展，也对堆积体地区的降雨型滑坡及渗流评价具有理论意义。

降雨型滑坡是我国主要的地质灾害之一，尤其在西南山区。基于典型非饱和土边坡的降雨试验及其物理模拟，运用非饱和土土力学等理论和数值方法对降雨作用下非饱和土的气-液耦合对非饱和土力学性质及其边坡稳定性的影响开展研究。建立了非饱和土固-液-气耦合模型，利用砂柱排水实验成果验证了耦合模型的正确性。气体对于雨水的下渗有一个阻滞作用，土体变形也会导致土体内部孔隙率减小和渗透性降低，气-液耦合与流-固耦合没有考虑到土体三相的相互作用，是不够精确的。孔隙气体迁移和土体变形对湿润锋的推进有一个延缓和阻滞作用。流-固耦合没有考虑到气体对雨水渗透的阻滞作用，与固-液-气三相耦合相比，流-固耦合情况下雨水下渗得稍快；气-液耦合没有考虑到土体变形会导致的孔隙率减小和渗透性降低会阻滞雨水的入渗以及气体流通，与固-液-气三相耦合相比，气-液耦合情况下孔隙水压力，孔隙气压力和稳定性系数变化更快，孔隙气压力最大值也与固-液-气三相耦合情况有所差异。非饱和土各向异性对土坡渗流场的影响与土坡深度及土坡位置有关。对Green-Ampt入渗模型进行了修正，并通过模型试验验证，试验结果表明该修正入渗模型具有较好的适用性。堆积层土质边坡破坏模式的发展过程主要可以分为三个阶段，坡脚侵蚀破坏—坡顶拉裂面的形成—滑坡失稳。降雨强度、雨型和初始含水率对滑坡形成产生影响。低强度、长历时降雨导致的滑坡滑动距离更远，破坏程度更高。该研究将有助于非饱和土渗流研究的推动，也对将降雨型滑坡的渗流分析具有意义。