渗流作用下孔隙水压力对坡面固体物质起动的机理研究

The loosen solid materials fail to form debris flow under seepage effect is one of the most common disasters in mountainours areas, especially post Wenchuan Earthquake, the high frequency of slope-debris flow affected the safety of human life and properties, as well as ecological environment. Presently, more researches of mechanics theory and experiments are focused on the solid materials failure, initiation condition and movement process, but less attentions are paid on the pore water pressures variation of loosen solid materials under seepage flow. Thus, based on the chosen slope model, the project analyze the mechanism problem of pore water pressures, through debris flow dynamics firstly, take mechanics analysis with infinite simal body to set up dynamic fomula, resistance fomula and critical thickness formula under saturated seepage flow effect; further more, to test and verify the theory results right or not, the project carry out the model experiment on condition of different discharge and slope gradient, and analyze the mechanism of pore water pressure during solid materials initiation process; last, take field experiment and observation, to analyze the characteristics of water content, pore water pressure in saturated/ unsaturated seepage condition in debris flow source area, as well to testify the critical initail thickness and probe the initiation mechanics problems of debris flow under seepage flow, which have a significant meaning on guiding the debris flow prevention and mitigation in advance.

渗流作用下泥石流源区固体物质失稳、起动形成泥石流是山区最为常见的灾害之一，尤其汶川地震后，坡面泥石流常常直接威胁灾区人民生命财产安全和生态环境。目前，降雨条件下坡面固体物质失稳、起动形成泥石流等机理研究较多，而渗流作用下坡面固体物质起动机理较少。因此，在选择坡体模型的基础上，首先从泥石流动力学入手，通过力学分析，建立饱和渗流作用下坡面固体物质起动的动力表达式、抗水动力表达式，根据力学平衡原理，建立固体物质起动的临界厚度判别式；其次，通过物理模型试验对动力和临界厚度表达式进行验证及修正，分析孔隙水压力在坡面固体物质起动过程中的作用机制；最后，开展泥石流源区坡面土体在饱和/非饱和渗流条件下孔隙水压力、含水量等原位试验、观测，分析孔隙水压力、含水量在泥石流起动过程中的变化特征，验证坡面固体物质起动的临界厚度，探讨泥石流源区固体物质在渗流条件下的起动机理问题，对指导泥石流灾害防治具有重要意义。

渗流作用下泥石流源区固体物质失稳、起动形成泥石流是山区最为常见的灾害之一，坡面、沟道型泥石流对灾区人民生命财产安全和生态环境造成极大的威胁。针对目前泥石流防治工程中物源计算存在误差大，计算机理认识不清的问题，提出了解决复杂水动力条件下固体物质是否移动的科学问题。研究在大量实地调查和分析的基础上，通过概化建立了平直型均值坡体模型，通过力学分析，以饱和渗流条件以及表面径流+渗流条件为研究动力条件，构建了该水动力条件下坡面固体物质起动的动力表达式以及临界厚度模型；在此基础上，通过室内水槽实验分析了饱和渗流条件下孔隙水压力对坡面固体物质起动的作用机制，发现了孔隙水压力对坡面固体物质起动具有较大的促进作用，在泥石流起动过程中均会出现细颗粒溢出、粗颗粒骨架坍塌的过程；同时根据模型试验对建立的动力表达式和临界厚度模型进行了验证，研究表明恒定流量饱和渗流作用下泥石流起动的动力表达式实验值与计算值误差介于1.3%~24.2%，恒定流量饱和渗流+表面径流作用下泥石流起动的动力表达式实验值与计算值误差介于2.9%~23.3%；恒定流量渗流作用下泥石流起动的临界厚度模型实验值与计算值误差介于6.5%~34.0%，恒定流量饱和渗流+表面径流作用下泥石流起动的临界厚度模型实验值与计算值误差介于42.0%~63.8%，具有一定的合理性。