西北典型黄土塬边滑坡地貌演化与平衡预测研究

Loess landslide induced by agricultural irrigation is the most serious geohazards type in Northwest Loess Plateau, which severely restricts the development of the local economy and society. At this stage, most of the new loess landslides occurred along the backscarps of the early landslides as well as their lateral edges. This phenomenon for such landsliding processes is defined by landslide evolution, which is characterized by multi-phases at one cross-section profile and occurrence in a group along the platform margins. The current understanding of this new issue is still at the stage of qualitative description. The mechanisms for such dynamic evolution are rarely been studied. Hence, this study mainly focused on this topics followed by research flow "phenomenon identification"→"theory study"→"development forecasts". The research is composed of building database of landslide geomorphic evolution, reveal the landslide evolution process, and obtain landslide evolution model as well as prediction the steady state of landslide evolution. First, the law behind landslide evolution can be built by the establishment of geomorphic evolution database. Second, mechanisms controlling the landslide evolution can obtained by simulation modeling on basis of experiments on undisturbed loess and monitoring of irrigation hydrological process. On these bases, the evolution model for loess landslides along platform margins can be summarized. Finally, based on the above research results, the steady state of landslide evolution along loess platform margins can be predicted by perdition of stepped stage of landslide evolution, hydrological response simulation, as well as stability evaluation of future slope. Meanwhile, volume for water and soil erosion can be also assessed according to the balance scene of landslide geomorphic evolution predicted. It will provide a very useful reference for the current disaster prevention and mitigation. Clearly, this study is not only of theoretical significance, but also important potential application in future.

黄土滑坡是西北黄土塬区农业灌溉诱发的地质灾害，严重制约着当地经济社会的发展。现阶段，黄土塬边滑坡主要是早期滑坡后壁及两侧台缘的再次失稳，呈现出纵向多期性、横向群发性的地貌演化特征。当前对这一新问题的认识仍停留在定性描述阶段，其动态演化过程和演化机制还缺少系统性研究。本项研究拟按照"客观现象→理论总结→发展预测"的思路，开展黄土塬边滑坡地貌演化过程、演化机制、演化模型及演化平衡场景预测研究。首先，通过建立黄土塬边滑坡地貌演化数据库，揭示演化过程和规律，其次，通过黄土力学实验以及灌溉水文过程监测，开展演化台缘稳定评价，揭示黄土塬边滑坡地貌演化机制，总结演化模型；最后，在上述研究的基础上，开展滑坡地貌演化进程预测、水文响应评估和复合斜坡稳定性评价，最终预测滑坡地貌演化平衡场景，评估滑坡侵蚀，为当前防灾减灾工作提供参考。可见，本项研究不仅具有理论意义，也具有重要的应用价值和应用前景。

黄土滑坡是西北黄土塬区农业灌溉诱发的地质灾害，严重制约着当地经济社会的发展。现阶段，黄土塬边滑坡主要是早期滑坡后壁及两侧台缘的再次失稳，呈现出纵向多期性、横向群发性的地貌演化特征。本项研究拟按照“客观现象→理论总结→发展预测”的思路，开展黄土塬边滑坡地貌演化过程、演化机制、演化模型及演化平衡场景预测研究，取得了如下进展：（1）将黄土滑坡演化从概念层面提升到相对独立的科学层面进行针对性的研究，通过详尽的野外调查和分析，将黄土滑坡演化分为纵向演化和横向扩展，进而表现为滑坡群，厘定了黄土滑坡演化过程，提出黄土滑坡演化模型;（2）针对黄土塬边滑坡，通过解析滑坡演化过程，揭示了滑坡事件对斜坡地质结构以及坡体应力分布的影响，尤其是发现坡脚堆积滞水效应、凹地形汇水效应以及灌溉强化作用，共同造成滑坡后缘坡体水位抬升较快，坡体非饱和增湿明显，造成滑坡后缘更易发生失稳，揭示了黄土滑坡的纵向演化机制;（3）揭示了滑坡对后期台缘稳定性的重要影响，以黑方台为例，揭示了滑坡演化对地下水位抬升的抑制作用，建立起演化进程中，黄土台塬面积、滑坡方量与水位关系模型，在灌溉量不变的情况下，随着滑坡的不断发生，地下水存在峰值水位，尤其是发现当前地下水仍未达到峰值，滑坡风险仍在加剧，预测了未来黄土滑坡新增方量和塬面退缩面积。通过本项目持续攻关，打破黄土滑坡演化仅停留在概念层面的现状，将滑坡演化提升到一个新的科学高度予以凸显，揭示了滑坡演化的关键过程与驱动机制，初步解决了黄土滑坡演化平衡这一关键科学问题，搭建了演化模型，丰富了我国黄土滑坡已有研究体系，对当前黄土塬边滑坡防灾减灾形势的研判和决策提供了理论支撑。