Influence Of Rainfall Infiltration On Stability Of Carbonaceous Shale Cutting Slope With Weak Interlayer

As a kind of weak structural layer,the weak interlayer often appears in the carbonaceous shale slope engineering,which is one of the main factors affecting the stability of the slope.When the rainwater infiltrates,the weak interlayer is easily muddy or softened,resulting in a decrease in strength and instability of the slope.Therefore,it is of great theoretical significance and engineering practical value to study the influence of rainfall infiltration on the stability of carbonaceous shale cutting slope with weak interlayer.Based on the National Natural Science Foundation of China(No.51374042),this paper takes the carbonaceous shale slope of the weak interlayer road from Hechi to Du'an Expressway in Guangxi as the research object,and uses the numerical analysis software Geo-studio to establish the calculation model and analyze the rainfall inflow.The seepage characteristics and stability of the soft interlayer carbonaceous shale slope during the seepage process provide a basis for engineering practice(1)The carbon shale is made into a test sample,and the basic physical and mechanical parameter values are obtained through an indoor test.The V-G model was used to fit the permeability coefficient and volumetric water content of the carbon shale and weak interlayer unsaturated zone,and the relationship between permeability coefficient and volumetric water content and matrix suction was obtained,which provided a reliable basis for the calculation model.(2)According to the form of the cutting slope of the selected road section,the SEEP/W module in the numerical analysis software Geo-studio is used to establish a suitable road slope model.Combining local meteorological data to design eight different rainfall options.The simulation analysis shows that rainfall infiltration affects the distribution of pore water pressure inside the slope,and the seepage field also changes;the wetting front at the slope mainly extends along the weak interlayer to the interior of the slope and forms in the weak interlayer.The bulge and the expansion rate are more obvious;when the rainfall continues for a certain period of time,there will be a sudden change in the pore water pressure at the depth of the interlayer,showing a "V" shape,and the pore water pressure will decrease.(3)In order to analyze the stability variation of the carbonaceous shale slope with weak interlayer under rainfall conditions,the SLOPE/W module in the numerical analysis software Geo-studio is used to numerically calculate the slope stability.The results show that the greater the rainfall intensity and the longer the duration,the more obvious the slope stability is affected by rainfall.When the slope contains a weak interlayer with high permeability and water intensity,the slope stability is more susceptible to rainfall.The effect of infiltration;when the weak interlayer is exposed at the top of the slope,the slip surface slides along the weak interlayer at the exposed position of the slope,and the slip surface of the slope is slipped out at the foot of the slope;The smaller the dip angle of the weak interlayer,the greater the influence of rainfall on the slope stability and the greater the rate of decline of the stability coefficient.