Study Of The Influence Of Controlled-Fissures On The Formation Of Granite Residual Soil Rainfall-Induced Landslide In Southeast Of Guangxi Province

The southeast of Guangxi province is an area where granite residual soil landslides occur intensively and is deeply affected by the landslide.It is of great significance to explore and understand the key causes of such disastrous landslides.Therefore,this paper targets Rong county in southeastern Guangxi province as the research area,and takes the granite residual soil rainfall-induced landslide as the research object and takes the water and soil interaction of the landslide as the core vein.By means of data collection,field investigation,numerical simulation and laboratory model test,the types,characteristics and distribution of fissures in the granite residual soil slope are statistically analyzed,and the characteristics of the controlled-fissures that have important influences on the formation of the landslide are determined.The mechanism of the water and soil interaction of the landslide is analyzed.Finally,the influence of controlled fissures to the mechanical catastrophic process of the landslide pregnancy is revealed.The main findings are as follows:(1)The controlled-fissures of the granite residual soil landslide belongs to the weathered fissures,which are mostly fissures at the back edge of the landslide and with the characteristics of inclined to open space,long extension length and large extension depth.(2)The failure mode of granite residual soil slope has a common characteristic,and the formation of the landslide goes through four stages: the stage of rainfall infiltration,the stage of deformation and destruction of the lower slope,the stage of block sliding,and the stage of flow-slip destruction..The sliding surface is shallow.The instability types include block slip and flow slide failure.(3)The water and soil interaction by rainfall infiltration are represented the increase of soil moisture content and the violent fluctuation of pore water pressure.The stable value of soil mass volume moisture content at depth of 0.3m and 0.5m is 54.3% and 62.4% respectively,and the peak value of the pore pressure is 1.815 k Pa and 2.383 k Pa respectively.(4)The controlled-fissure can significantly affect the process of water and soil interaction,which is reflected in the difference between the initial change time and response time of soil moisture content and pore water pressure.For the non-fissure slope and the fissure slope,the initial change time difference of soil moisture content is 28 min,and the initial change time difference of pore water pressure is 12 min.(5)The controlled-fissure change the path of rainwater infiltration and enhance the infiltration capacity of the slope,affect the time-varying regularity of soil moisture content and pore water pressure and the distribution of the seepage field,which accelerates the slope instability.At the same time,the controlled-fissure can limit the position and shape of slide surface to a certain extent,thus affecting the failure mode of slope.