Study On Stability Influencing Factors And Instability Model Of High Loess Fill Slope

In the loess region of Northwest China,with the increase of large-scale engineering projects,there are numerous casualties and property losses caused by the instability of loess high fill slope every year,therefore,the stability of loess high fill slope needs to be taken seriously.This paper takes the typical loess high fill slope in the northwest as the research object,and comprehensively investigates the catastrophic characteristics of the loess high fill slope.According to Liu Dongsheng et al.(1985),the loess is divided into three zones:I zone sand loess,II zone typical loess and III zone sticky loess;taking I zone Jingbian,Tongxin loess samples,II zone Fuxian,Qingyang loess samples,and III The Xi'an and Lingbao loess samples were combined with laboratory tests to analyze the engineering properties of the fill loess in different areas.The influencing factors of loess high fill slope stability were simulated by Geo-studio software.The limit slope height of loess high fill without support was studied by using Flac 3D numerical simulation software.The instability mode of the high fill slope is verified by an example.The instability mode of the high fill slope is finally based on the instability mode and the actual situation of the fill slope(first fill and support),and the suggestions for setting the anti-slide pile position under different instability modes are given to increase the loess high fill.The research content can provide theoretical and practical significance for disaster prevention and mitigation of high fill slope in loess area.The main research results are as follows:(1)The results of laboratory tests show that Jingbian,Tongxin,Fuxian,Qingyang,and Xi'an and Lingbao six kinds of loess samples appearing from east to west,from south to north,the particles are gradually thicker,and the cohesion is gradually increased,the law of internal friction angle gradually decreases.(2)Through the analysis of the influencing factors on the stability of loess high fill slope,it is concluded that the filler factors(gradation,compactness,water content),fill slope factors(fill slope type,slope height and slope ratio)and inducing factors(surface water,groundwater and loading)have great influence on the stability of loess high fill slope,while the original slope factor(original slope slope type and slope ratio)has little effect on the stability of loess high fill slope.(3)The stability coefficient between the linear fill slope and the stepped fill slope and the fill height are in a power series relationship;the limit slope height of the straight loess high fill slope increases with the slope and height of the fill.Gradual reduction;stepped loess high fill slope,with the reduction of single-stage slope ratio,the ultimate filling height shows an increasing trend.(4)Under natural conditions,the instability mode of the linear loess fill slope with a 35°slope of 10m to 70m is:from progressive backward damage to creep-pull failure.When the slope of the fill is from 45°to 60°,the instability mode is as follows:from progressive backward damage to creep-pull failure and then to shifting failure.When the slope of the linear fill is 70°,as the height increases,it shows a progressive backward to shifting failure instability mode.(5)Under natural conditions,the stepped fill slope,with the increase of the fill height,the instability mode of the 1~#and 2~#slopes is dominated by the shift type;when the height reaches 75m,due to the effect of the slope weight and the internal contact relationship of the fill slope and the original slope,the instability mode is changed to creep-pull type.The instability mode of 10~#slope type is changed from progressive backward damage to creep-pull type.Under the same conditions,the stepped loess high fill slope has better stability than the straight fill slope.(6)The ideal position of the anti-slide pile retaining mode of the creep-pull-breaking instability mode is suitable near the foot of the fill slope;The shifting instability mode anti-slide pile retaining position is relatively close to the trailing edge of the fill slope.Progressive backward instability mode of the anti-slide pile retaining position is relatively close to the middle of the front edge of the fill slope.