地震和降雨耦合作用下黄土边坡失稳机理与预防方法

Earthquake and rainfall are the two main kinds of factors to cause landslide. However, the coupling effect of multi field has not yet to be considered in the slope stability analysis due to the lack of conclusive evidence of slope failure induced by coupling fields. Some cases of massive failure of loess slopes, caused by the Ms 6.6 Earthquake of Minxian-Zhangxian County, Gansu Province, China in 2013 and the strong rainfall before the earthquake, should be the conclusive coupling event under earthquake and rainfall around the world. Those landslides within the Minxian-Zhangxian Earthquake show the features associated with soilflow, in which the landslide of Yongguang Village led to a serious loss, 14 households buried and 12 persons dead. In this application, we firstly analyze the variation law of water content and shear strength of loess soil in one case of slope differing with the precipitation by means of seepage test controlled by artificial precipitation and dynamic torsional shear test. Secondly, three coupling patterns of earthquake and rainfall, i.e. the rainfall before, or after the earthquake, and the special case of liquefaction slippage, are considered in the shake table test. By this way, the failure mechanism and slippage mechanics of loess landslide induced by the coupling effect of earthquake and rainfall could be summarized. Meanwhile, the calculation method of safety factor of loess slope under coupling effect of earthquake and rainfall will be proposed. Based on the probability analysis and fuzzy information theory, then, we provide respectively a probabilistic method to assess the failure risk of loess slope under the coupling action of earthquake and rainfall, and a prediction method of disaster region for the coupling case of landslide. At the last, the theory and method of safety design for the engineering practice to prevent the failure disaster of loess slope induced by coupling effect of earthquake and rainfall. This research project takes effort on the new case of slope failure under multi field and the purpose is to answer the key theoretical problems of the coupling failure of loess slope. Consequently, the expected innovative results of this project have an obvious significance at both aspects of science and application to ensure the urban and rural development and engineering construction through preventing and controlling the potential risk of multi-field-induced landslides in the loess region of China.

地震和降雨是诱发黄土边坡失稳滑动的两大主要自然因素，但目前对两者耦合作用下黄土边坡稳定性的研究甚少。2013年甘肃岷县漳县6.6级地震引发的大规模黄土滑坡是国内外地震和降雨耦合诱发灾害性滑坡的一个确凿例证。本项申请拟通过人工降雨渗透试验和动三轴扭剪试验，研究不同降雨条件下黄土边坡内含水量的时空变化规律及土体静动抗剪强度变化特征；基于振动台模拟试验，分析厘清震前降雨、震后降雨及液化滑移等三种地震和降雨耦合作用情况下的黄土边坡失稳机理与滑移机制，提出地震和降雨耦合作用下黄土边坡安全系数的计算方法；借助概率分析和模糊信息理论，研究建立地震和降雨耦合作用下黄土边坡失稳的概率性风险评价和致灾区预测模型；综合给出防范黄土边坡失稳的安全设计理论与方法。本项目申请以解决多场耦合诱发黄土边坡失稳这一新现象的关键科学问题为目标，预期创新成果对黄土地区城乡建设和工程建设的潜在风险防控具有重要科学意义和应用价值。

地震和降雨是诱发黄土滑坡的两大天然因素，二者产生耦合作用时滑坡致灾风险更高。基于此，本项课题开展了地震和降雨耦合作用下黄土边坡失稳机理与预防方法的研究工作。利用自主设计的人工降雨设备开展了野外黄土边坡人工降雨渗透试验，研究了不同降雨条件下黄土边坡降雨渗透范围及含水量时空变化规律；通过动扭剪等一系列室内试验，结合降雨渗透试验结果研究了降雨后黄土边坡不同部位土体静动强度的定量变化规律。通过实施多种降雨条件下黄土边坡振动台模型试验，研究了黄土边坡的变形演化规律、破坏模式与失稳机理；构建了基于振动台试验的模型失稳判别指标，提出了地震和降雨耦合作用下黄土边坡安全系数的计算方法。通过对甘肃南部区域的滑坡危险性区划，建立了因子权重法与概率分析法相结合的滑坡危险性评价方法；基于黄土地震滑坡历史资料，建立了可对黄土滑坡致灾范围进行快速预测的模糊信息优化处理模型。研究了地震和降雨不同耦合模式作用下的黄土边坡安全坡角的变化规律，分析了黄土边坡前缘和后缘的安全避让距离与降雨条件、坡高、坡角、边坡土体抗剪强度、地震动峰值加速度之间的定量关系，提出了黄土边坡安全避让距离的定量确定方法，并建立了黄土边坡稳定性及其可能致灾范围的工程应用判定指标体系和预测方法。