Mechanical Model Of Slope Failure Characteristics And Stability Under Rainfall Combined With Groundwater Infiltration

Rainfall and groundwater infiltration directly lead to a strong hydrological response inside slopes,weakening the mechanical parameters of rock and soil and reducing overall slope stability.This can often result in geological disasters such as landslides.Therefore,studying the hydrological response characteristics and damage characteristics of slopes under this working condition is of great significance for the monitoring,early warning,disaster prevention and mitigation of such disasters.To this end,this study explores the hydrological response characteristics of soil during infiltration by conducting infiltration tests on different soil columns in the laboratory.Additionally,slope simulation tests under rainfall combined with groundwater infiltration were carried out,and the development characteristics of different soil slope failures were studied.Based on these experiments,combined with the infinite slope stability analysis model,the study analyzes the influence of depth change on slope stability in each zone.The following main results were obtained:(1)For non-cohesive soils,the infiltration characteristics show two stages of infiltration,denoted as "I and II".The I stage is mainly affected by rainfall infiltration in the superficial layer and shows "top-down" saturation.The II stage is primarily affected by groundwater infiltration and exhibits a "bottom-up" saturation pattern.For silty clays,infiltration characteristics show only one infiltration process and are mainly affected by groundwater infiltration.Regardless of the infiltration conditions,the moisture content increases with the increase of infiltration time,with the rate of increase being relatively large in the early stages of the test and finally tending to 0 with the gradual decline of the infiltration process.The rate of increase of moisture content,pore water pressure,and earth pressure at the same location of the slope increases with the increase of rainfall intensity and groundwater infiltration head height.(2)For non-cohesive soil slopes,under the combined action of low rainfall intensity(30 mm/h)and low infiltration head(1.40 m),uninterrupted continuous failure(S’ failure)mainly occurs on the slope,with a single large-area failure("S" failure)occurring in the later stage of the test.However,under the action of low rainfall intensity combined with high infiltration head(1.70 m、2.00 m)or high rainfall intensity(90 mm/h)combined with high infiltration head,"S" damage mainly occurs on the slope,and the higher the groundwater infiltration head,the earlier the slope is damaged.For silty clay slopes,regardless of the infiltration conditions,only S’ damage occurs on the slope.Rainfall and groundwater infiltration will form seepage channels near the slope surface and foot,continuously eroding and washing the slope,with the final failure depth of the slope being shallow.The failure mechanism is manifested in the rapid increase of soil moisture content,resulting in the continuous decline or even dissipation of the matrix suction inside the soil,and the increase of pore water pressure,resulting in the continuous decline of the effective stress of the soil and promoting the development of slope failure.(3)The stability coefficient of the slope decreases with the increase of the depth of each layer.The stability of the rainfall saturation zone is affected by two factors:rainfall infiltration causing a decrease in the mechanical strength of slope soil and an increase in sliding force,and the increase of the osmotic effect generated by seepage with the depth of the rainfall saturation zone.The stability of the transition zone is mainly related to the depth of the rainfall saturation zone and the depth of the transition zone and is mainly affected by rainfall infiltration.The stability of the groundwater saturation zone is determined by the depth of the rainfall saturation zone,transition zone,and groundwater saturation zone,but the softening effect and osmotic effect produced by groundwater infiltration play a dominant role.(4)The development characteristics of different soil slope failures were compared and analyzed,and it was found that the seepage channel formed by the groundwater infiltration effect led to continuous erosion damage at the foot of the slope,which played a dominant role in the stability of the slope,and the higher the groundwater infiltration head,the more obvious the effect;Not only that,the stability coefficient at the foot of the slope is always less than 1.0 at the beginning through stability analysis,and its duration decreases significantly with the increase of groundwater infiltration head,which is consistent with the failure characteristics presented by physical experiments,which further indicates the important influence of groundwater infiltration on slope stability.The research results have certain guiding significance for the evaluation of slope stability under the condition of rainfall combined with groundwater infiltration.