Stability Analysis Of Clastic Rock Slope With Mudstone Interlayer Under Rainfall Infiltration In Guangxi

Based on the project "Research on prevention and control of geological disasters in clastic rock area of Guangxi" supported by the land and Resources Department of the Guangxi Zhuang Autonomous Region in 2014.Statistical analysis, numerical simulation and theoretical analysis were adopted to the distribution, development characteristics, failure mechanism and key factor of geological disasters of clastic rock area in Guangxi. The relationship between rainfall and stability of clastic rock slope are studied. The main research contents and results are as follows:1. Geological hazard date of Guangxi clastic distribution area from 2005 to 2013 were statistical analysis.The results show that landslide is the most common geologicd hazards in Guangxi clastic area. The main type of landslide small and shallow. One of the main induced factors of clastic landslide is rainfall.2. The relationship between landslides and rainfall in Guangxi clastic rock area was analysis.The results shows that that there is a good correlation between the landslides and rainfall process of 1 to 4 days. Landslides induced by rainfall occur mainly during the storm peried. And the time of landslides lags behind the peak time of rainfall and is closer to the peak time with increasing of rainfall intensity.3. A large number of historical survey data of landslide of Guangxi clastic rock area were counted to analysis the physical and mechanical properties. Statistical results shows that Guangxi clastic rock landslides occur in the interlayer of mudstore and clastic rock area.The reason is that the shear strength is low of soil shear strength decreasing and become lower impacted by water,so the mud zone is easy to be slip surface.4. A generalized model with clastic rock and mudstone interbedding was set up to simulate and analyze the slope stability with muddy intercalations in clastic rock area by SEEP/W and SLOPE/W module of Geo-studio numerical analysis software.The simulation results show that when rainfall intensity reaches a certain degree it may form a temporarily relatively stagnant water district on the mud surface. The rainfall intensity comes higher and time comes longer, the more temporarily relatively stagnant water district performance more significantly.The reason is that when mudstone is soaked by water, the soil saturation is higher, pore water pressure is bigger, and shear strength of soil is lower,so a layer of weak zone is founed, and the slope stability is reduced. The results shows that the smaller the slope gradient is the greater impact of rainfall to internal slope moisture content, the smaller to slope foot;The potential sliding surface of landslide induced by rainfall is mainly distributed in relatively impermeable surface or contact surface of hard and soft soil layer.