Influence Of Rainfall Infiltration On The Stability Of Residual Soil Slopes With Different Parent Rocks

Landslides pose a huge threat to the safety of the people,and comparative analysis of residual soil slopes with different parent rocks under the influence of rainfall infiltration has not been studied much.Therefore,relying on the 2020 National Land Research Project of the Guangdong Provincial Department of Natural Resources,"Research on the Prevention and Control of Artificial Slopes in Key Mountainous Counties(Cities)in Guangdong Province",this paper conducts research on the influence of different parent rock residual soil slopes on rainfall infiltration.It is of great significance in disaster reduction.In this paper,the stability analysis of three different types of parent rock residual soil slopes in five regions of Guangdong Province under rainfall conditions is carried out through field experiments,laboratory experiments,theoretical analysis and numerical simulation.The Mein-Larson rainfall infiltration model was improved and verified,and then three different parent rock residual soil slopes were used for stability analysis under rainfall infiltration conditions.The main research results are as follows:(1)Measure the volumetric water content of the slope through field tests,conduct basic physical property tests of soil,obtain soil mechanical property parameters and hydraulic property parameters of unsaturated soil,and analyze the soil properties of residual soil of different parent rocks: residual soil The higher the soil saturation,the smaller the internal friction angle,and the shear strength first increases and then decreases;under high matrix suction,the Boltzman model is less effective in characterizing the hydraulic properties of unsaturated soils,and the Brutsaser model is less effective in the entire matrix suction range.The fitting effect is better than the Boltzman fitting model,and the Van Genuchten fitting model has the best adaptability and the best fitting effect.(2)The Mein-Larson infiltration model was improved considering the nonlinearity of the initial water content distribution,and the reliability of the improved model was verified by finite element simulation and slope volumetric water content data respectively.The two models have better effect,which lays a theoretical foundation for the following study on the influence of wetting front infiltration depth on slope stability.(3)By theoretically solving the homogeneous soil slopes of three different parent rocks,it is found that the safety factor obtained by the strict segmentation method based on the M-P criterion is slightly smaller than the safety factor obtained by the finite element method,which is more safe;With the infiltration of the wetting front,the safety factor decreases more rapidly.When the groundwater level is approached,the safety factor decreases slowly,and when the groundwater level is reached,the safety factor reaches the minimum value.(4)The finite element simulation of quartz sandstone,mica-quartz schist and granite residual soil slope was carried out by Geo-Studio software,and it was found that under the condition of rainfall intensity R=200mm/d for one day,the safety factor of quartz sandstone residual soil slope was 1.338,a decrease of 3.88%,the safety factor of mica-quartz schist residual soil slope is 1.697,a decrease of 1.11%,and the safety factor of granite residual soil slope is 1.333,a decrease of 2.91%,all three can remain stable.(5)Quartz sandstone residual soil slope and granite residual soil slope increase with the increase of rainfall intensity,and the volumetric moisture content of soil in different parts of the slope increases rapidly and tends to be saturated;mica quartz schist residual soil slope increases with rainfall intensity The change of volume moisture content of soil in different parts of the slope is small.(6)Quartz sandstone residual soil slope and granite residual soil slope increase with the increase of rainfall time,the volume water content of soil in different parts of the slope increases continuously,and the pore water pressure also gradually increases;mica quartz schist residual soil slope increases with the increase of rainfall.With the increase of rainfall duration,the variation range of soil volume moisture content and pore water pressure in different parts of the slope is smaller,and the range affected by water infiltration is also smaller.(7)In the weak rainfall-free infiltration stage,the rain intensity and the nature of the soil itself,that is,the water sensitivity,jointly determine the reduction range of the safety factor of the slope;in the heavy rainfall-with pressure infiltration stage,the soil permeability and The nature of the soil itself,that is,the water sensitivity,controls the decrease of the safety factor of the slope.