Stability Analysis Of Loess Slope Considering Barometric Pressure In Soil Under Rainfall-Evaporation Condition

Landslides are common geological hazards in the loess area.There are many factors that cause landslides,but rainfall is the most important factor.About 70% of landslides are related to rainfall.Rainfall infiltration reduces the matrix suction in the soil,which leads to a decrease in soil strength and slope instability.Evaporation also affects the distribution of volumetric water content in the slope,which in turn affects the slope stability.In order to study the impact of rainfall-evaporation on slopes,the article comprehensively simulates the transient seepage field and stability of the rainfall-evaporation process during the seepage process with different slopes,different rainfall intensities,and different rainfall forms,taking into account the pressure.The specific work and results of the article are as follows:(1)Summarized unsaturated soil strength theory,water-gas two-phase seepage theory,permeability coefficient estimation method,climate-soil boundary conditions,and slope stability calculation method.(2)The gas phase and water phase seepage in the slope are stored in the competition,and the water in the slope will move around the high pressure area.(3)Analysis of the transient seepage field of unsaturated loess slopes found that the presence of gas phase will reduce the permeability of the slope,resulting in the slope surface moisture content is higher than that without considering the gas phase,and the greater the rainfall,the greater the influence of the gas phase.The depth of influence will also be affected,considering the slope of the gas phase is lower than that without consideration.The form of rainfall will affect the slope seepage field,the earlier the maximum rainfall occurs,the deeper the seepage depth.(4)The existence of the gas phase will reduce the stability of the slope.The greater the rainfall intensity,the greater the impact,and the smaller the slope,the smaller the impact.When the rainfall is less than 50mm/d,the effect of gas relative stability is basically negligible.(5)The water movement in the evaporation process is divided into two parts.The first part is the evaporation of the surface soil.The evaporation of the surface soil will be affected by the previous rainfall.The greater the previous rainfall,the greater the initial evaporation rate of the slope.The second part is the deep soil seepage towards the deeper soil under the action of water potential difference.This part of water will cause the strength of the deep soil to decrease.(6)The slope can be divided into three stages in the evaporation process,namely the stable evaporation stage,the stage where the evaporation intensity changes with the change of water content,and the early stage of the water vapor diffusion stage.The three-stage evaporation process occurs when the rainfall is large.Hourly rainfall only occurs in the latter two stages of evaporation process.(7)Considering that the stability of the slope of the gas phase increases rapidly,without considering the stability of the gas phase,there is a "lag effect".The smaller the slope angle,the earlier the "lag effect" occurs.