Study On Slope Stability Of Expansive Soil In Coal Measures Under Rainfall Infiltration

There are many coal-measure strata in multiple generations distrubuted in Yichun and Pingxiang areas of Jiangxi Province.The coal measure soil in this region contains secondary minerals such as montmorillonite and illite.It has poor water-holding performance and weak cementing capacity between layers.After the continuous rainfall,the coal-measure soil often suffers from shallow landslide damage,which affects road passage and even threatens the driving safety.Because the physical and mechanical properties of coal-measure soils have certain regionality,the variation rule of unsaturated soil strength and the failure mechanism of slope instability in the coal-bearing strata in this region under the condition of rainfall are not clear yet.Therefore,in this paper,the mechanical properties of coal measure expansive soil and its slope stability were studied based on the exposed coal measure soil in the area of jiangxi wanzai to yichun expressway.The main work contents are as follows:(1)Experimental study on mechanical properties of coal measure expansive soil in laboratory.Through field slope sampling,the physical and mechanical properties of coal measure expansive soil were tested in laboratory,and obtained the shear strength of coal measure expansive soil under the effect of different coal content and water content.It provides a reference for the design and protection of coal measure expansive soil slope in this area.(2)Numerical simulation of slope stability of coal measure expansive soil under rainfall conditions.Considering that the slope is in saturated-unsaturated dynamic change process under the condition of rainfall,the numerical models of the slope in transient saturated zone and unsaturated zone of coal measure expansive soil are established.The change of volumetric water content of coal measure soil slope is simulated.The changing law of seepage field and safety factor of slope is analyzed under different soil permeability coefficient,rainfall intensity,rainfall duration and slope ratio.It provides a reasonable suggestion for the design parameters of coal measure expansive soil slope engineering.(3)Experimental study on slope model of coal measure expansive soil under artificial rainfall condition.Based on the actual engineering background,we made a large-scale outdoor model of coal measure expansive soil slope.The continuous rainfall test was carried out on the slope model of coal measure expansive soil by using the artificial rainfall device system,the change rule of water content and matric suction of the slope was monitored,and the deformation and failure mode of the slope of coal measure expansive soil under the action of continuous rainfall was observed.The seepage field and shear stress of the model slope under rainfall condition are simulated by finite element method.The failure mechanism and evolution characteristics of coal measure expansive soil slope were discussed.