Law Of Water Infiltration In Macroscopic Cracks Of Loess And Its Influence On Slope Failure

The loess landslide is the most serious in the Loess Plateau area.According to statistics,80% of the landslide is induced by rainfall and irrigation.Moreover,a large number of macroadvantageous channels such as fissures and drainage tunnels are developed on the edge of the loess tableland to provide convenient channels for water infiltration,thus inducing a series of loess disasters.Taking Miaodian landslide in southern tableland of Jingyang as the research object,the loess landslide,macro structural plane and basic physical parameters in the study area were analyzed through field investigation,data collection and laboratory tests.On this basis,physical model tests were carried out to study the macroscopic dominant infiltration mode,the evolution trend of crack propagation and the failure mode of slope,and to reveal the influence mechanism of macroscopic structure on the failure mode of slope.Finally,Geo-studio software was used to simulate the seepage field of the physical model test to explore the changes of water flow in the slope body.The main conclusions of this paper are as follows.(1)According to the infiltration morphology of structural plane,the loess macro structural plane is divided into parallel plate structural plane(planar dominant channel like fissure)and columnar structural plane(tubular dominant channel like sinkhole)through field investigation and literature review.The macrodominance infiltration can be divided into two infiltration modes: wall-sticking flow and jet flow,and the simultaneous existence of wall-sticking flow and jet flow is called mixed flow.(2)The expansion and evolution trend of cracks is summarized,which can be divided into two ways.One is the retrogressive erosion on the rear wall of cracks,which leads to the continuous receding and cutting under the action of water flow;the other is the latent erosion effect on the bottom of cracks,which leads to the formation of dark caverns at this depth.Combined with the geomechanical model,the slope failure can be divided into two conditions according to different infiltration modes.The first one is the infiltration dominated by wall flow,whose failure stages can be divided into four stages: erosion-softening,erosion-collapse,submergence-expansion,creep-crack.The second type is based on jet infiltration,whose failure stages can be divided into: erosion,erosion-softening,erosion-collapse,erosion-expansion,plastic flow-through;(3)Taking the unit width slope as the research object,using the torque method to carry out a simple mechanical analysis to get its stability evaluation coefficient,and conclude that its stability is related to the geometric characteristics of the collapse body,the slope hydrostatic pressure,the original crack bottom water content.(4)The numerical simulation analysis was carried out on the seepage field changes caused by macro-dominant infiltration in the physical model test,and the slope seepage fields with different crack depths and different irrigation sizes were obtained.The seepage field changes were consistent with the physical model test phenomena,and the macro-dominant infiltration mechanism inside the slope was analyzed.