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.