Study On The Failure Mechanism For The Earthy Bank Slope During The Running Of The Three Gorges Reservoir

The earthy bank slope is one of the typical geological disasters,which distributed to about 50% bank-line in the Three Gorges Reservoir.Studying on the failure mechanism of the earthy bank slope during the reservoir operation is the national demand for prevention and reduction of geological disasters in the Three Gorges Reservoir,as well as the logical demand of reducing disciplinary development.Research achievements have scientific significance for supporting the early warning,prevention and control of the serious geological disasters.Relying on the natural science funding(key)project of Chongqing,i.e.,“Study on the failure mechanism for the earthy bank slope during the running of the Three Gorges Reservoir”,and three typical earthy bank slope,Gongjiafang bank slope engineering,Shennvxi bank slope and Liangshuijing bank slope,this paper studied the failure mechanism of the earthy bank slope during the reservoir operation by using some research methods,such as indoor small scale model test,indoor shear test,fracture mechanics,seepage mechanics.This paper obtained the following several main achievements:(1)This paper proposed the equivalent structure model of the earthy rockmass and the equivalent calculation method of shear strength parameters.(2)Based on shear strength test of the earthy rockmass,this paper revealed shear strength parameters' varying law;there exists one matrix partical size to obtain the minimum inter friction angle and exists one clay content(inclosion)to obtain the maximum inter friction angle.Action mechanism of shear strength of the earthy rockmass could be divided to inclosure acting stage and matrix acting stage,and inclosure acting stage experienced the three stages,i.e.,particle contact?vertical compress and level shear ?matrix contact;matrix acting stage included the three stages of matrix climbing,matrix rolling to critical location and matrix jump.(3)This paper revealed the laws of pore water pressure,deformation and failure,varying microtopography by using small scale model test.Based on deformation and fairlure characteristics this paper proposed the evolutionary pattern of the earthy bank slope deformation and failure: micro-collapse in the toe of slope?sedimentation caused by soaking softening?microcrack growth in the trailing edge of slope?crack development in the toe of slope ?extensiveness collapse in the toe of slope?entire sliding of slope.(4)This paper put forward the soaking softening tenso-shear failure mechanism for earthy bank slope under the reservoir filling,confirmed the quantitative relation between soaking softening scope and tension crack in the trailing edge of slope,and deduced fracture mechanics formula for tenso-shear failure of the earthy bank slope soaking softening.(5)This paper proposed compression-shear failure mechanism caused by seepage driving under the reservoir falling.Based on compression-shear acting on the earthy bank slope by seepage-driving force during the drawdown in the Three Gorges this paper established compression-shear failure model by seepage-driving force,and improved the calculation method of seepage-driving force,then imposed compression-shear failure criteria by seepage-driving for the quasi earthy bank slope.(6)This paper proposed the transfer coefficient method for the earthy bank slope stability calculation considering the seepage force.