降雨作用下黄土滑坡的启动机制模拟试验研究

Loess Plateau areas is featured by fragile geological environment in China, concentrated rainfall，coupled with the unique structure of the loess and susceptibility to collapse on wetting，In recent years，rainfall induced loess landslides have become the most frequent、widely affected and damaged the most serious geological disasters in loess area. The project revolves around the current weaknesses in this research area，Taking the example of Xi'an Baqiao landslide as research prototype, and the combination of geotechnical test，physical model test, numerical simulation and theoretical analysis is adopted. Based on which, the initiation mechanism of loess landslides under different rainfall intensity is studied，reproducing the whole process of landslide. Based on the newly built large-scale rainfall model test system platform and numerical analysis，and through the multi-angle monitor and real-time data collection of deformation，moisture，stress and strain in the slope, the trigger condition of loess landslide caused by rainfall is explored, and the activation response mechanism will be revealed；the changing processes of physical, water physical and mechanics property are analyzed respectively. and the infiltration as well as migration progress of water is revealed. Furthermore, reciprocal relationship between rainfall and slope failure evolution process is explained. Moreover, the failure modes of loess landslide triggered by rainfall will be summarized. The results of this research has important theoretical value and reference value, for it can not only provide scientific test basis for disaster prevention and mitigation as well as human settlements security in loess area.

我国黄土高原地质环境脆弱、降雨集中，加上黄土独特的结构性与水敏性，致使降雨诱发的黄土滑坡成为该地区发生最频繁、影响面最广、破坏最严重的地质灾害。本项目紧紧围绕当前该研究领域中的薄弱环节，以降雨诱发的西安灞桥滑坡实例为研究原型，采用室内岩土试验、物理模拟试验、数值模拟和理论分析相结合的方法，开展不同降雨强度条件下黄土滑坡的启动机制研究，再现滑坡的全过程。拟基于新建的大尺度降雨模型试验系统平台和数值分析，通过对坡体形变和土体内部水分、应力应变等指标的多角度监测和实时数据采集，探索降雨诱发黄土滑坡的临界触发条件，揭示其启动响应机理；解析在滑坡不同阶段坡体内部的物理、水理、力学性质等参数的变化特征，揭示水在坡体内部的入渗与运移规律，尝试破解降雨活动与坡体破坏演化过程之间的互馈关系，并概化其失稳模式。项目研究成果可为黄土地区的防灾减灾、人居安保提供科学的试验依据，具有重要的理论价值和现实意义。

中国黄土高原地貌破碎，地质环境脆弱，频发的滑坡、崩塌、地面沉陷等自然灾害造成的人员伤亡和财产损失惨重，严重制约了经济发展，然而其中90%以上的滑坡都因降雨诱发。黄土遇水后导致的胶结减弱、自重增加、裂缝扩展、强度降低等反应均可降低边坡的稳定性，开展降雨诱发滑坡的大型物理模型试验，研究雨水的入渗运移规律和边坡的失稳破坏过程，能够完善黄土灾害相关理论，填补该方向研究空白，并对黄土滑坡防灾减灾工作有重要的参考价值和现实意义。.论文以2011年“9•17”灞桥滑坡为研究原型，通过现场调查，掌握了滑坡发生的地质背景，通过进行室内试验获取了土样的物理力学参数，建立三维地质模型开展人工降雨诱发滑坡的大型物理模型试验，实时监测了滑坡发生的全过程；利用数值模拟方法研究了原始边坡在降雨条件下土体参数的响应特征及其时空分布规律。基于对土体水分、压力、应力等微观指标的时程分析，以及对表面裂缝、节理裂隙等宏观现象的归纳，从阶段性特征、力学机制两大方面探讨了滑坡孕育和发生全过程的内在机制。结论如下：.（1）试验过程中土体含水率和孔压随时间“S”型增长，前期和趋稳期增速小，而滑坡前后增速大，响应敏感度和增幅与深度成反比，顶部反应快且波动强烈，深部恰好相反。.（2）土体竖向应力随时间“反S”型变化，前期和稳定期因压密有小幅增加，而滑坡前后因位移加速应力大幅释放，但节理处的土体，竖向应力持续稳定增长；表面裂隙经历扩张→冲刷→填充的过程，表征连通性的拓扑学特征先升后降。.（3）从力学机制看，降雨的滴溅作用、淋滤作用引起了裂缝的扩张，基质吸力、孔隙水压力的改变影响了土体的抗剪强度，最终多因素叠加引发滑坡。.（4）瞬态渗流模拟和稳定性分析揭示了水分在坡面、顶面和垂直节理中入渗速度的差异特征，以及水平位移、垂直位移和最大剪应变的时空分布规律；古土壤层的低渗透性导致其含水率和孔压均要高于相邻的黄土层，其界面易成为软弱面。