Analysis Of Seepage Field And Stability Of Fractured Soil Slope Under Rainfall

Since the mid-twentieth century,because of the ever-increasing global warming,the frequency of extreme intense rainfall events and well vegetated slope failure events following the heavy rains in mountains are getting higher and higher.Rainfall is the main reason for inducing slope instability,understanding its damage mechanism and influencing factors plays an important role in the prediction and protection of landslide disasters.So far,the study of rainfall induced landslides has mainly focused on factors such as rainfall intensity,rainfall holding time,and initial water content.However,the study on the response process and response mechanism of groundwater to rainfall has not received sufficient attention.The first groundwater response to rainfall is the response of soil to rainfall,and soil structure is an important factor affecting the response process.A large number of cracks distribute on the slope surface due to shrinkage and bioturbation and other reasons,cracks are widely present in natural and engineered soils.The presence of fractures and their geometry,rainfall conditions,and initial water content in the soil can affect the seepage field and stability of the soil.Cracked soil is a key factor that causes geotechnical engineering problems such as slope failure,underground pollutant migration in dams,and dam destruction.The main research contents of this article mainly include the following aspects:(1)The fractured soil is regarded as a double-porosity system consisting of a fracture network and soil foundation,in which the fracture network is a large pore system and the soil-based system is a small pore system.The volume fraction of the fracture network is introduced as a known variable.Based on the V-G model,the relationship between matrix suction,water content and permeability coefficient of the fractured soil is deduced.The existence of fissures makes the soil-water characteristic curve of the soil change from a single peak characteristic to a double peak characteristic.(2)Under the premise of introducing the double-peak characteristic curve of fractured soil,based on a project in Hubei,under the conditions of heavy rainfall,two results about the water content and the pore water pressure with considering fractures and without considering fractures can be given(3)Observing the difference of the seepage field of the entire slope with and without consideration of the fracture.At the same time,the volumetric proportion of the measured parameters of the fracture network is introduced to investigate the effect of the change in the crack content on the seepage field of the slope with increasing rainfall duration.(4)Comparative analysis of changes in the slope safety factor with and without considering cracks and the final dangerous slip surface.Meanwhile,considering the change of the fracture network volume,it explores its influence on the safety factor.(5)Based on the Richard seepage equation of double-pore model and the Galerkin method,the seepage fields of the matrix and fracture network are obtained respectively and the rationality of the method is compared with the results of hydrus-1D.(6)Under the condition of rainfall,the effects of rainfall time and matrix width on the seepage were studied.The wet peak surface distributions of the matrix and the fracture network are compared,the former is steep and the latter is gentle.(7)The slope stability analysis shows that the greater the matrix width,the deeper the slope stability affected by rainwater infiltration,when the matrix width becomes smaller,the rainwater is close to uniform infiltration,and the depth of slope stability affected by rainwater infiltration becomes smaller.However,the increase in saturation makes the shear strength of shallow soils decrease more.