Influencing Factors And Reliability Analysis Of Loess In South JingYang Plateau

Landslide accidents of different scale occur year round in the loess area on the south bank of the lower reaches of Jing he River in Shanxi,the resulting casualties and economic losses are very serious.The traditional method of evaluating slopes,that is,the safety factor method,is obviously monotonous,and it is impossible to take into consideration numerous factors.On the basis of probability theory,the reliability theory has made a good development and supplement on the safety factor method.Therefore,this paper has done some preliminary exploratory work on the reliability analysis of the loess slope in south Jing yang plateau.First,a brief analysis of the influencing factors of slope stability was carried out,and then based on the soil-water characteristic curve test and the tri-axial test of unsaturated soils.Monte Carlo method is used to calculate the probability of slope reliability using Geo-Studio system software.The stability of the slope is evaluated according to the failure probability of the loess slope and the reliability index under different slope heights,slope angles and groundwater depths of the soil.The main contents and conclusions of this paper are as follows:?1?Several major factors affecting the stability of loess slopes are summarized.Internal factors such as bulk density,cohesion,internal friction angle,as well as slope height,slope angle,depth of groundwater level,etc.,among which soil parameters such as internal friction angle and cohesion are the main influencing factors.External factors such as earthquakes,irrigation,and climate and rainfall are the most important ones.Water is the most important factor in south Jing yang plateau,mainly including rainfall and large-area farmland irrigation,which causes landslides caused by groundwater elevation.?2?L₉ soil layer at the foot of the slope was used to make 13 sets of ring knives.Filter water method was used to determine the soil-water characteristic curve?SWCC?of the two paths of humidification and dehumidification.The analysis shows that the matrix suction gradually decreases with the volumetric moisture content of the soil sample;the dehumidification curve is located in the upper part of the humidification curve,reflecting the hysteresis characteristics of the SWCC,and a brief analysis of the phenomenon is performed.?3?The VG model was used to fit the data points and SWCC related fitting parameters were obtained.According to the unsaturated permeability coefficient model,the unsaturated permeability coefficients in the humidification and dehumidification processes are estimated,and the relationship between the unsaturated permeability coefficient and matrix suction of the L₉ soil layer is obtained.?4?The TFB-1 type unsaturated soil tri-axial tester was used to perform a CD test for controlling suction.After analysis,it can be concluded that the stress-strain curve changes from strain-softening to weak-strain softening,with the peak gradually becoming insignificant,and showing a gradually decreasing trend.?5?According to Fredlund shear strength theory,the characteristics of the extended three-dimensional Mohr-Coulomb failure envelope and stress point envelope are analyzed,from theand(_?6?-relationship curve calculated⁽?7?=13.06°,and then combined with The data obtained the shear strength formula of unsaturated soil of L₉ soil sample.?6?The Slope/W module in the Geo-Studio software was used to analyze the slope reliability using the Monte Carlo method.The results show that when the slope angle of the soil is reduced from 40°to 30°,the failure probability is obviously reduced,and the safety is obviously improved.When the slope angle of the soil continues to decrease,the change of the failure probability becomes slower.?7?The slopes of the slope height,the slope angle of the soil slope and the depth of the groundwater level caused a wide range of changes in the probability of failure of the slope.The order of magnitude of the impact from the largest to the smallest was the depth of the groundwater table,the soil Slope height and pile slope angle.?8?In this test,when the slope height of the soil is 20m,the angle of the soil pile is 40°,and the depth of the ground water table is within 4m,the slope is in a low-risk state;in the remaining six conditions,the slope is in a stable state.To a certain extent,it provides a reference for the prediction and evaluation of loess slope stability.