非饱和成层土边坡中漏斗型优势流的发生机理及其稳定性问题

In analyzing the problem related to precipitation-induced landslide, it is crucial to properly characterize the funneling process of pore water in layered soil slopes. This research focuses on the problems about the formation of funneling flow and its effect on the slope stability. Based on laboratory experiments, we investigate the criteria and mechanisms of the formation of funneling flow in the unsaturated layered soil slopes and the effect of funneling flow on the shear strength of soil layers. A new seepage model which can be used to characterize the funneling process in unsaturated layered soil slopes, is developed based on multiphasic poromechanics and unsaturated soil mechanics. And a new shear strength model is also developed in which the effect of funneling flow is considered based on the experiments in hydraulic and strength characteristics of unsaturated layered soils. By combining the proposed model and the most recent development in stability analysis, a new numerical analysis procedure is developed for analyzing the stability of unsaturated layered soil slopes during intermittent rainfall events. The numerical procedure is then implemented into a computer code. Experiments under proper monitoring are performed to simulate the seepage progress and the occurrence of funneling flow in layered soil slopes. The proposed theoretical model and numerical procedure are validated by comparing the simulations with experimental measurements. The results of this research will provide effective analytical method for the prediction of instability of layered soil slopes and control of geological and environmental hazards caused by the precipitation. And the reliable theoretical basis will be also developed for solving the hazard problems related with layered soil.

降雨入渗激励下非饱和成层土边坡中经常出现漏斗型优势流问题,有效模拟这种复杂的渗流过程是准确分析降雨诱发此类滑坡问题的关键。本研究针对漏斗型优势流的形成及其对边坡稳定性影响问题，基于室内模型试验，研究非饱和成层土边坡中漏斗型优势流的形成机理和过程机制及其对土层抗剪强度的影响规律；基于多相孔隙介质力学和非饱和土力学的基本原理，结合土体水力、强度特性试验，建立能够描述非饱和成层土边坡中漏斗型优势流过程的理论模型及抗剪强度模型；结合边坡稳定性分析的最新研究成果，提出降雨入渗条件下非饱和成层土边坡稳定性问题的分析方法，开发计算分析程序。开展模拟试验，利用实测边坡土体中的渗流过程、漏斗型优势流的发生及其对边坡稳定性的影响验证理论模型和分析方法的可靠性。本研究将为降雨诱发的成层土边坡失稳导致的地质与环境灾害问题的预测预报与防治提供有效的分析方法，并为其他有关成层土灾害问题的解决提供可靠的理论基础。

本项目围绕降雨入渗诱发非饱和成层土边坡失稳灾害机理的关键问题,结合理论模型、室内试验、数值模拟等多种手段对复杂的渗流条件下降雨诱发此类滑坡问题开展了深入的研究，主要研究成果如下：（1）考虑降雨入渗的非平衡效应，建立了定量描述土水特征关系动态效应的理论模型，开展室内试验，验证并发展了土水特征关系曲线的快速测定方法；（2）建立了非饱和土孔隙分布与核磁共振谱分布之间的定量关系式，利用核磁共振技术，能够快速有效测定非饱和细粒土土水特征关系曲线；与传统方法相比，这两种方法的建立使得能够有效地测定静态和动态条件下的土水特征关系曲线，大大节约测定时间，能够推动非饱和土在实际工程中的应用。（3）建立了考虑水力滞回效应的完整土水特征关系模型，进一步建立了任意含水量变化下的非饱和土渗流理论模型，开发了相应的计算机程序，开展了降雨入渗激励下非饱和土边坡渗流过程的分析；（4）开展了干湿变化下非饱和土的强度试验，建立了能够考虑含水量干湿影响的非饱和土抗剪强度公式；（5）结合非饱和土抗剪强度公式及局部安全因子法，建立了降雨入渗作用下非饱和成层土边坡的稳定性分析方法，并对现场边坡潜在滑动性开展了分析评价。这些公式与方法的建立为复杂降雨条件下非饱和成层土边坡的稳定性分析提供了初步的定量评价工具，并为其他有关成层土灾害问题的解决提供可靠的理论基础。