The Formation Mechanism Research Of The Cut Foot Type Loess Landslide Based On The Creep

Because of Special geological environment background,the loess tableland in the southbank of the Jing river has so much loess landslide,they has caused the degradation of the loesstableland, a large amount of the soil erosion and made the residents, near the loess tableland,huge threat to life and property damage.Through field investigating in the scope of thelandslides in the study area,we found a type of loess landslide causing by cutting the feet,thistype of loess landslide has the characteristics of the long time lasting,the bigger thickness,thedepth of sliding surface and the circular sliding.This paper has studied the formationmechanism of the loess landslide causing by cutting the feet basing on the creep of the loessand according to the method of cutting the feet,we divided this type loess landslide in thestudy area into lateral erosion type and slope toe excavation type.On this basis,we made someresearch about the physical and mechanical properties of the loess in laboratory,then used theFLAC3D numerical software to simulate the generating process of the cut foot type loesslandslide, at last we summarize some of the physical and mechanical characteristics of theloess in the study area and the formation mechanism of the cut foot type loess landslidebasing on the creep of the loess,the points mentioned below:(1)According to the method of cutting the feet,this paper divided the cut foot type loesslandslide into lateral erosion type and slope toe excavation type.The lateral erosion type iscaused by the lateral erosion by the Jing river;The slope toe excavation type is casused by theexcavation slope toe by the human activity.(2) Because of Special geological environment background,the moisture content of theloess gradually increases with the increase of the depth.(3)In conventional triaxial undrained shear test(CTC),how much moisture and confiningpressure determines the failure mode of loess.Under the condition of the low moisture contentor the low confining pressure,the failure mode of loess is the cracking damage.Under thecondition of the medium moisture content or the medium confining pressure,the failure modeof loess is the shear failure.Under the condition of the high moisture content or the high confining pressure,the failure mode of loess is the ballooning destruction.(4)In the confining pressure reduction triaxial shear test,when lower the confiningpressure,then the deviatoric increase,so the loess has deformation by compression.Theconfining pressure reduction rate has strong influence on the intensity of the loess,theintensity increases following the increase of the shear rate.(5)In the triaxial consolidation undrained creep test,under the condition of the samemoisture content and confining pressure, the amount of creep deformation of the soilincreases following the increase of the deviatoric stress level and the final creep also increaseswhen the soil has already been damaged.Under the condition of the same moisture content,theamount of the creep deformation of the soil decreases following the increase of the confiningpressure.Under the condition of the same confining pressure,the amount of the creepdeformation of the soil increases following the increase of the moisture content.(6)The cut foot type loess landslide numerical simulation results based on the creep ofthe loess,cutting slope foot is equal to the stress path of reducing confining pressure,thedeviatoric stress relative increase.Then cracking damage appears at the top of the slope,theplastic zone is bigger in the slope toe,developing to the internal,but fracture surface was notformed,the slope is still stable.When considering the loess creep characteristics,the slopedeformation accumulated with the passage of time.The tensile fracture surface near the topextends down along with the development of the deformation.The shear failure surface in themiddle of the slope extends upward along with the development of the deformation.At last,theshear failure surface intersects the tensile fracture to some point.The soil moves to lateral,awell fracture surface was formed,then slope slided.