| In the western Sichuan mountainous area,there is a kind of soil with a large particle size span,which is formed by the collapse of landslides and other mixed soils due to historical earthquakes or natural actions due to collapse,landslides,etc.Natural slopes composed of such soil are often deformed and destabilized under factors such as rainfall,earthquake loads and traffic loads,resulting in a large number of loss of life and property.Because the talus mixed soil in the western Sichuan area has unsaturated characteristics,exploring the permeability characteristics of such mixed soil slopes under rainfall conditions has important reference significance for the stability evaluation of slopes and landslide disaster prediction in western Sichuan.In this paper,the western Sichuan talus mixed soil is taken as the research object(hereinafter referred to as “mixed soil” or “mixed soil in western Sichuan”).The variation law of the saturated permeability coefficient of the mixed soil sample under different coarse material content and different dry density is studied through the indoor permeability test.And the soil-water characteristic curve under different dry density is studied,and then the statistical model is used to predict the permeability coefficient function of the mixed soil under unsaturated conditions.Using the Geo Studio software,the finite element model of the mixed soil slope under six rainfall conditions is established.And the distribution characteristics of volumetric water content and pore water pressure of mixed soil slope and slope stability under factors such as the rainfall duration,rainfall intensity,previous rainfall events,slope inclination and saturation permeability coefficient are analyzed.This study mainly draws the following conclusions:(1)The saturated permeability coefficient of landslide slope mixed soil has a nonlinear relationship with the coarse material content and dry density: when the coarse material content is less than 30%,the permeability coefficient changes slowly with the increase of the coarse material content;when the coarse material content is greater than 30%,the growth rate of permeability coefficient becomes larger;And the saturation permeability coefficient decreases with increasing dry density.The soil-water characteristic curves of the mixed soil samples at different dry densities are well fitted by the Van Genuchten model,and the model parameters change with the dry density.The unsaturated permeability coefficient of the mixed soil has a nonlinear relationship with the matrix suction,and when the matrix suction is constant,the greater the dry density of the mixed soil,the greater the permeability coefficient.(2)The surface and shallow soils of mixed soil slopes are most affected by rainfall,while deep soils are less affected by rainfall.Therefore,attention should be paid to the possibility of shallow landslides on mixed soil slopes.In the early period of rainfall,the decrease of surface soil matrix suction and slope safety factor is much greater than in the later period.(3)When the rainfall intensity is constant,the longer the duration,the greater the depth of the mixed soil slope affected by rainfall,and the lower the safety factor;When the total amount of rainfall is constant,the rainfall with low intensity during long duration is more detrimental to the stability of the slope than the rainfall with high intensity during short duration.And the greater the rain intensity,the deeper the wet front of the slope develops,the greater the weakening of the slope stability.(4)The early rainfall and slope inclination both affect the entire rainfall infiltration process by affecting the distribution of the initial seepage field of the mixed soil slope: The greater the early rain intensity,the smaller the change in pore water pressure on the surface of the slope during the later rainfall,and the lower the safety factor,but the smaller the safety factor decreases.The greater the slope inclination,the deeper the wet front moves down,which is more detrimental to stability.(5)When the saturated permeability coefficient of the soil is less than the rainfall intensity,the surface soil of the mixed soil slope reaches saturation,and the rainwater forms runoff along the slope surface,and the safety factor is almost unchanged;when the saturated saturation of the soil is greater than the rainfall intensity,the greater the permeability coefficient,the greater the rainfall,the greater the depth of infiltration,and the worse the slope stability. |
PDF Full Text Request