Study On Interface Effect And Stability Of Loess Fill Slope

In order to solve the problems of small expandable space and the shortage of available land resources,large-scale construction projects of Cutting Hills to Build Cities and Gully Land Reclamation are carried out in Yan'an city.During the implementation of this project,many stability problems of excavation and fill loess slope are involved.The stability of the loess fill slope is affected by many factors and the loess fill slope has a feature of "three-sides and two-bodies and one-water(interface,basement surface,free surface,filling body,foundation body,environmental water)",and especially the interface plays a leading role in the stability of loess fill slope.Therefore,it is of great theoretical significance and engineering practical value to study the interface effect and the stability of the loess fill slope.This paper takes the loess fill slope of Cutting Hills to Bulid cities and Gully Land Reclamation projects in Yan'an city as the research object,based on the field investigation and field sampling of the original slope and fill slope in Yan'an Nangou and Yan'an new district,the physical and mechanical parameters of loess are firstly obtained by indoor geotechnical test and CTC triaxial shear tests.Then the interface effect and instability mechanism of the loess fill slope under rainfall is studied through laboratory model test,combined with multi-conditions numerical simulation calculation,the stability of the fill slope under rainfall and the change of slope angle,as well as the influence and sensitivity of related parameters of the boundary zone between the fill slope and original slope and the earth fill on the stability of the fill slope are analyzed.The main results and conclusions are as follows:(1)Based on the laboratory model test,the variation laws of water content and pore pressure of the fill slope and its interface with the original slope under the action of rainfall is revealed,holding that the interface effect shows that the interface is a dominant infiltration channel and there is a hysteresis phenomenon of rainfall infiltration along the interface.Under the action of rainfall,the deformation and failure mode of the loess fill slope is shallow sliding,and its instability process is local mud flow damage at foot of slope?rill erosion at the middle of the slope?tension cracks develop near the slope shoulder?local slip caused by surface erosion?cracks near the shoulder of slope increase and expand and deepen?shallow sliding may occur at the slope shoulder.(2)Based on Geo-studio numerical software,the influence of different rainfall conditions on the stability of fill slope is analyzed.The results show that in a certain rainfall time,the rate and range of the decrease of stability coefficient of fill slope increase with the increase of rainfall intensity.Under the same rainfall intensity,the stability coefficient of fill slope decreases with the increase of rainfall duration..Under the condition of invariant rainfall and peak rainfall intensity,different rainfall processes have little influence on the final stability of fill slope.(3)Through the numerical simulation of the stability of the fill slope under the condition of rainfall and the change of slope angle,the influence laws of rainfall and slope angle on the stability of the fill slope is revealed,and the results show that when the angle of fill slope ?35°,the plastic deformation of the fill slope occurs only within the boundary zone.When the angle of fill slope >35°,shear deformation occurs at the foot of the slope due to stress concentration,with the increase of,the plastic deformation of the foot of the slope increases,at the same time,the plastic deformation of the boundary zone is also expanding,when the angle of fill slope ?55°,the combination of the two parts of plastic deformation causes the slope to slide along the boundary zone.(4)Through Midas/GTS numerical software and sensitivity analysis method,the influence degree and regularity of boundary zone and earth fill parameters on the stability of fill slope are revealed,The results show that the internal friction angle of the boundary zone has the greatest influence on the stability of the fill slope and the influence degree in turn is as following: the cohesion of the boundary zone,the inclination of the boundary zone,the internal friction angle of the earth fill,the filling length,the cohesion of the earth fill.