黄土结构性与水敏性的互馈作用及其滑坡灾变机制

Taking the loess landslide in south Jingyang plateau as a case study, the basic characters of structure and water sensitivity of loess will be researched and described quantitatively. Based on unsaturated soil mechanics theory, a series of mechanical laboratory test research over a wide range of suction and under different stress paths will be carried out, which is to disclose the interaction between the structure and water sensitivity and their contribution to the loess physical and mechanical changes. A long term field observation test will be studied so that the moisture content, the matric suction and the evaporation of different position and depth under various conditions such as SWCC, artificial rainfall, agriculture irrigation and drip irrigation will be studied and obtained. On the basis of this, the law of water infiltration in loess and the interaction mechanics mechanism between the loess structure and water sensitivity will be clarified and discovered, and "how to explain the process of water sensitivity of loess" will be answered. And large-scale physical model test research of different cases such as rainfall, flood irrigation, drip irrigation and so on will be conducted. By means of multiple parameter observation system, the developing pattern and speed of the wetting front in loess under different working conditions and the real-time quantitative data and the changing rule of strength, deformation and stress of the slope will be studied, and the failure process of loess landslides and the mechanics mechanism caused by water will be illuminated, which will provide scientific basis to the prevention and cure of loess landslides.

以泾阳南塬黄土滑坡为研究原型，对黄土结构性与水敏性的基本特性进行定量研究与描述；基于非饱和土力学理论，开展大吸力、不同应力路径条件下的黄土力学试验研究，揭示黄土结构性与水敏性的互馈作用及其对黄土物理力学性质变化的贡献；建立野外现场长期观测试验基地，获取长周期渗水（SWCC）、人工降雨、农业漫灌、滴灌条件下，不同位置和深度黄土含水率、基质吸力、蒸发量等多参数时程数据，阐明水在黄土中的入渗规律，揭示黄土结构性与水敏性的互馈作用力学机制，回答黄土"怎样水敏"的问题；开展降雨、漫灌、滴灌等不同工况下的大型物理模型试验研究，通过布设多参数观测系统，获取不同水事活动下土体中的湿润锋面推进方式、速度以及坡体的强度、变形、应力等实时同步定量数据和变化规律，阐明水致黄土滑坡的变形破坏过程及力学机理，为黄土滑坡防治提供科学依据。

本项目主要围绕黄土的“结构性”与“水敏性”探讨我国黄土高原地区水致滑坡的力学机制；在此基础上，结合现场大型试验、室内物理模型试验及数值分析等方法，揭示了水致滑坡在不同条件下的变形破坏机理及成灾模式。（1）通过开展研究区现场长期渗透试验及室内黄土增湿试验，揭示了黄土的“水敏性”及“水敏过程”；基于黄土的构度指标分析了不同条件下黄土的动强度衰减规律，探讨了黄土“结构性”与“水敏性”的互馈作用；（2）利用自行设计的模拟降雨系统，设计并进行了三组不同雨强下的大型黄土边坡人工模拟降雨试验，得出降雨条件下大型黄土边坡现场试验的变形破坏规律，总结出该类边坡的水分入渗规律和变形破坏模式；（3）通过室内物理模型实验及数值分析，揭示了不同降雨形式、不同坡体结构对黄土斜坡变形破坏过程的影响，揭示了该类滑坡的破坏模式及其诱发机理；（4）采用可用于坡顶和坡面灌溉的灌溉装置，得出了灌溉条件下浅表层黄土滑坡的变形破坏规律，揭示了该类滑坡的破坏模式及其诱发机理。通过上述研究进展，基本阐明了水致黄土滑坡的变形破坏过程及力学机理，对于我国地质灾害防灾减灾中黄土滑坡的防治具有重要意义。