Study On Weakening Effect And Stability Evolution Regularity Of Rainfall Seepage In The Debris Landslide

The geological structure of the Three Gorges Reservoir area is complex and diverse,the topography is different,and it is affected by many factors,such as rainfall,reservoir and human activities,and the frequency of geological disasters is higher.Many landslide cases in its reservoir area show that: under the condition of rainfall,especially extreme rainfall,the occurrence of landslide has close relation with rainfall intensity,rainfall and rainfall holding time,the effect of rainfall infiltration on the shear strength and deformation parameters of slope rock and soil has a certain effect on the displacement field and the stability of the slope.In this paper,the internal evolution law of the internal seepage field,displacement field and stability under the condition of rainfall is analyzed at first,based on this,the paper studies the effect of the weakening effect of rainfall infiltration on the displacement field and the stability of the slope under the condition of two kinds of rainfall intensity and rainfall,and draws the following conclusions:1.The change law of shear strength parameters and deformation parameters of rock and soil under different water content conditions,cohesion,internal friction angle and elastic modulus decrease with the increase of water content,and Poisson's ratio increases with the increase of water content rate.2.Through the numerical simulation of seepage field,displacement field and stability of three kinds of rainfall conditions,it can be found that,with the rainfall,the infiltration line in the slope gradually rises with the increase of rainfall,and the higher the rainfall intensity,the higher the elevation of the infiltration line is;Under the condition of rainfall,the gap water pressure at the top of the slope is the most obvious,the second is the middle of the slope,and finally the middle leading edge position of the slope,and the contour cloud of the displacement field under the rainfall condition shows that : displacement deformation is mainly concentrated in the middle and leading edge of the slope,and the greater the rainfall intensity,the more obvious displacement changes,displacement in the rainfall,the medium-term growth rate isfaster,late changes gradually slow;it is found that the stability coefficient decreases with rainfall,the rainfall intensity is greater,the stability coefficient is lower.The analysis of the stability coefficient with time changes under different rainfall conditions shows that the greater the rainfall intensity,the greater the decrease of the stability coefficient.3.Under certain conditions of rainfall intensity,according to the analysis of the displacement contour cloud,the maximum value of the slope displacement field considering the seepage weakening effect is 0.08 m,and the maximum displacement value without considering the weakening effect is 0.03 m,which is 166.7% higher than the maximum displacement value without considering the seepage weakening effect.Therefore,considering the effect of parametric weakening effect on slope displacement is relatively large;The numerical simulation results show that the minimum stability coefficient of the non-weakening effect is 1.335,while the minimum value considering the weakening effect is 0.978,and the reduction amplitude is 27.49% compared with the non-considered weakening effect,this also proves from the side that the weakening effect caused by rainfall infiltration is unfavorable to the overall stability of the slope.4.Under the condition of constant rainfall intensity,the weakening parameters of the slope model are assigned in stages,the simulation results show that: compared with the displacement curve without considering the weakening effect,the displacement curve shows obvious mutation trend,the main reason is the seepage weakening effect caused by rainfall infiltration.Under the condition of constant rainfall,the parameter weakening of the slope model is assigned,and the analysis results are compared with the horizontal comparison,the more obvious the parameter weakening amplitude,the larger the corresponding displacement deformation,and the smaller the corresponding stability coefficient.5.By comparing and analyzing the numerical simulation of two kinds of weakening conditions,we know: the maximum displacement value under operating condition 5 and working condition 6 is increased by 12.50% and 6.25% respectivelycompared with the phase weakening parameter assignment.The stability coefficients under two operating conditions are 16.83 and 3.30%,respectively,compared with the weakening assignment of the phased parameters.