基于降雨响应的黄土-基岩型滑坡失稳机制分析以宝鸡市麟游县岭南滑坡为例

为探索黄土-基岩型滑坡的降雨响应机制,以麟游县岭南滑坡为例,利用滑坡宏观变形破坏数据、岩土体测试与模拟计算相结合的方法,讨论了暴雨、连阴雨下岭南滑坡的地下水水位响应特征,相应应力路径下土体应力应变特征,对黄土-基岩型滑坡的破坏机制进行了研究。初步揭示:(1)滑坡体为粉质黄土状黏土,滑床为砂砾岩,渗透系数小,具有隔水性质。(2)黄土泥流与块体滑动是岭南斜坡的主要运动失稳方式。暴雨天气时黄土泥流频发,块体滑动的出现与连阴雨有关。(3)与降雨103mm的暴雨天气相比,连续降雨235.5mm,斜坡地下水位明显升高。(4)滑坡体粉质黄土状土具有剪胀特征。在暴雨背景下,表层土体孔隙水压力易消散,诱发低速运动的黄土泥流; 在连阴雨背景下,地下水水位以下的滑动面剪切破坏过程中,剪胀孔隙被地下水迅速补充,诱发的剧烈块体滑动,具有高危险性。

FAILURE MECHANISM ANALYSIS OF LOESS-ROCK LANDSLIDE UNDER RAINFALL-A CASE STUDYTAKE THE LINGNAN LANDSLIDE IN LINYOU COUNTY OF BAOJI CITY FOR EXAMPLE

In order to explore rainfall response mechanism of loess-bedrock landslide, the paper has discussed ground water level response characteristics of Lingnan landslide under rainstorm and successive rain and soil stress-strain characteristics under corresponding stress path. It takes the Lingnan landslide in Linyou county as an example. It combines macroscopic deformation and failure data of landslide, geotechnical test and analog computation. Moreover, the failure mechanism of the loess-bedrock landslide has been studied in the paper. The paper shows the preliminary results as follows. Firstly, the landslide mass is silty loessial clay. The landslide bed is glutenite. The mass and bed are featured by lower osmotic coefficient and high imperviousness. Secondly, the muddy loess flow and block slide are the main models of motion instability of Lingnan landslide. Upon rainstorm, the muddy loess flow breaks out frequently. In this sense, the block slide is in connection with successive cloudy-rainy weather. Thirdly, the ground water level of the slope has increased drastically in 235.5 mm successive rain compared with 103 mm rainstorm. Fourthly, the silty loess of landslide mass is characterized with dilatancy. In case of a rainstorm, surface soil pore water pressure easily diffuses, subsequently, induces low-speed muddy loess flows. Under successive cloudy-rainy weather, dilating pores are timely replenished by ground water during shear breakdown of slide planes below ground water level. Drastic block slide arising from this cause can make great hazards.