Study On The Loess Landslide Mechanism Of Slope Toe Excavation

The Loess Plateau is an important arena for human activities. Loess region’s economyhas been a huge development in recent years. But its unique topography makes a lot oflimitations for local economic development and human living, which makes the cutting slopephenomenon to be more common. This kind of behavior caused a lot of serious geologicaldisasters, which brought a great threat to production and living of local residents. Northernmargin slope of Bailu tableland of Xi’an city produced landslide and killed32people inSeptember2011, causing widespread concern at home and abroad and many factories wereshut down. In this background, the loess landslide caused by human engineering activitiesmake a large number of field surveys, topographic mapping and data analysis, and select theloess landslide caused by the slope toe excavation as the main object of study. The basiccharacteristics of the slope toe excavation loess landslide make the statistical analyses of theinfluence factor of slope toe excavation. On this basis of sliding mode of slope toe excavationclassified, the slope toe excavation induced mechanism of loess landslide is studied.Some main innovative ideas are got as follows in this paper:(1) Through wild field investigation and documentation analysis, that the slopeexcavation formed unloading joints, joints direction approximate unanimously with the slopetoward, To some extent, joints control the slope stability. Landslide edge cracks were "U"shape and "double ears"-shaped distribution. Different slope heights, there is a differentmoving speeds. The slope height70m above is more serious harm. Excavation types oflandslides distributed as follows: high degree concentration and bands distribution.(2) According to the excavation speed and the influence factors of slope toe excavationof loess landslides, which are divided into: quickly unload model of loess landslide,excavation and rainfall coupled model of loess landslide and excavation and freeze-thawcoupled model of loess landslides. The typical cases were analyzed by each type landslidemechanism and the landslide characteristic. And to every type of landslide mechanisms andcharacteristics were analyzed.(3) The triaxial shear RTC stress path tests carried out on undisturbed saturated loess and unsaturated loess. The test results show that the RTC test was contraction under shear andstrain hardening characteristics. Under the RTC stress path test results show that the soil shearstress is lower and easier to destroy. Undrained soil deformation process of destruction, thefailure process is so quick that the excess pores. Excess pore water pressure accelerateddestruction of deformation of the soil.(4) Under different slope toe excavation condition makes the numerical calculation ofslope stability. The results show that the slope angle of certain cases, the slope height controlsthe stability of the slope. Its stability gradually decreases with excavation angle increasing,this change of the slope toe excavation distance is lesser which effect is not obvious.Stratigraphic structure’s influence on the slope toe excavation is: the more complex structure,the smaller impact of excavation. Excavation distance of the slope influence is: with theincrease of excavation distance, the safety factor of a slope gradually reduced, and there is aturning point in the process of excavation.(5) According to the slope failure modes are divided into: stress control type, slope anglecontrol type, control type stratigraphic structure, excavation footage control type. Accordingto the slope failure modes are divided into: stress control type, slope angle control type,control type stratigraphic structure, excavation footage control type. According to differentstress is divided into: tensile failure zone, compression and shear slip zone, reduced and shearfailure zone.(6) Based on the stress distribution characteristics and physical and mechanicalproperties changes of slope deformation and slope structural stress analysis caused by slopetoe excavation, which explains the slope excavation resulting in cracks generated andexpansion and deformation until failure mechanics. Considered slope toe excavation is adecisive factor cause the slope instability.