基于GIS的浅层碎石土滑坡降雨入渗-稳定性实时评价模型研究

Shallow debris soil landslide happeded in soft metamorphose-rock area and induced by rainfall is the most widely distributed and serious disasters in Qinba Mountain area. However, research on stability evaluation of these landslides are limited to one or two dimensional model, neglecting in-depth analysis the mechanism of rainfall infiltration under the condition of low rainfall intensity (the rainfall intensity is less than the saturated permeability coefficient of soil) and unsteady rainfall intensity. Taking the landslide metamorphose-rock debris soil as the study object, this proposal is intended to analyze the rainfall infiltration law based on the large scale soil column experiments, establish the rainfall infiltration model under the condition of arbitrary rainfall intensity considering the saturated-unsaturated characteristics of debris soil， construct a real-time rainfall infiltration stability evaluation model coupled with the 3D limit equilibrium stability model, based on raster data format of Geographic Information System(GIS). In addition, a set of a quantitative stability evaluation method based on GIS spatial data will be proposed to deal with the rainfall-induced shallow debris landslide in Qinba mountain area . With improvement of the accuracy and timeliness of the stability evaluation for the rainfall-induced shallow debris landslide, it has high theoretical significance and value.

降雨诱发的浅层碎石土滑坡是秦巴山区分布最广且最严重的灾害类型。针对此类滑坡稳定性评价的研究较少，多局限于一维或二维模型，且忽略了对低雨强（降雨强度小于土体饱和渗透系数）及变雨强条件下降雨入渗机理的深入分析。本课题拟通过室内大尺寸土柱试验，分析该区变质岩风化所形成碎石土滑坡在任意雨强条件下的降雨入渗规律，充分考虑碎石土的非饱和-饱和特性，建立任意雨强条件下的降雨入渗模型；将非饱和土抗剪强度理论、三维极限平衡模型和地理信息系统（GIS）相结合，建立基于非饱和土抗剪强度理论的三维极限平衡模型；并在此基础上，实现降雨入渗-稳定性评价耦合模型的GIS程序开发。课题以正在监测的浅层碎石土滑坡为背景进行理论验证和应用，并面向秦巴山区降雨诱发的浅层碎石土滑坡建立一套切实可行的基于GIS空间数据的变雨强降雨入渗-稳定性定量评价方法，提高滑坡稳定性评价的精度和时效性，具有重要的理论意义和实用价值。

项目在对秦巴山区碎石土滑坡调查的基础上，选取典型滑坡，通过现场监测及室内非饱和水力学试验，进行了土水特性与土体结构相关性研究，揭示了该区碎石土饱和/非饱和渗流特性与其结构参数的关系，为建立秦巴山区碎石土水力学参数库奠定了基础。开展了典型斜坡降雨入渗过程现场监测、室内大尺寸土柱试验及数值模拟，揭示了该区斜坡降雨入渗规律；提出采用分段计算的方法，利用考虑斜坡倾角的修正Green-Ampt模型对湿润锋运动过程进行分段描述，具有较好的适用性。研究提出了改进型非饱和渗流模型，可用于快速计算非饱和条件下斜坡的含水率和吸力响应。研究探索了基于有限差分算法的非饱和渗流控制方程、简化非饱和抗剪强度理论与无限斜坡模型的斜坡降雨入渗-稳定性评价模型；提出了一种简化的考虑滑坡物理-力学过程的滑坡失稳判别指标，即基于一维非饱和-饱和渗流与非饱和无限斜坡模型计算确定滑坡启动的降雨强度-持续时间（I-D）临界曲线，结合GIS栅格数据结构，以及降雨时序、区域岩土参数分布与斜坡上覆土体厚度等进行降雨条件下区域斜坡稳定性评价，为分析降雨诱发滑坡渗流过程与稳定性演化趋势分析提供了理论支撑。