The Generation And Evolution Mechanism And The Motion Featur Of Maliugou Slope In Qingchuan County, Sichuan Province

Maliugou slope is a typical soft-foundation reverse layered rockmass slope,whosespecial slope structure determines unique formation and evolution mechanism,and theleading edge of the slope always forms large-scale potential unstable rockmass orpartial collapse,and brings more serious disasters.AIn-depth study on Maliugou slopeformation and evolution mechanism and the motion featur has important the oreticalvalue and practical significance to prevent such slope engineering disaster efficently.The paper studied systematically on slope structure,rock deformation and failurecharacteristics,and characteristics of spatial distribution of the Maliugou slope,andbuilt four deformation and failure modes of slope.On the basis of in-depth analysis offormation and evolution of influencing factors,built the geomechanical model of slopeformation and evolution,the use of2D discrete element dynamically simulatedformation and evolution of slope,and established the slope formation and evolutionmechanism modes,in order to evaluate and predict the stability of the potential unstablerockmass.Combined with rockfall kinematics calculation theory and rockfall riskstatistical analysis software,the movement characteristics of rockfall under its ownweight and strong earthquake projectile role is studied deeply. The details and resultsare as follows:1)The slope of the study area is soft-foundation type of medium~gentle reverseslope,the upper escarpment exposes dolomites and the lower part of the gentle slopeexposes calcareous sericite phyllite.As the incised valley and the role of variousinternal and external forces caused stress redistribution and stress concentration of theslope,soft foundation slope appears bending,compression,creep deformation,resultingin dolomite produce dumping crack or overall slip.According to signs of existing deformation and failure and space distribution position, it is divided into four unstablerockmasses,eastside of the surface rock of potential unstable rockmassI wasdestructed wedge in projectile destruction by“5.12”Wenchuan Earthquake, volume upto5.0×103m3, the collapse of the total cubic capacity of more than90%of the rockfallstoped the plot from the cliff foot10m to140m range.2) Built the four deformation and failure modes of the rockmass in the study area：①the slipping failure mode;②the dumping failure mode;③the falling failure mode;④the strong earthquake throwing failure mode.3)The formation and evolution of the geomechanical model of slope in the studyarea is the pressuring induced creeping-cracking-dumping,divided it into unloadingrebound and steep crack formation,the leading edge of slope deformation(pressure-induced creep-crack-dumping)and the deep of slope deformation（pressure-inducedcreeping-cracking）in three stages.The paper simulated rockmass fracturing-thedumping of the dynamic causes of process when valley cut to1300m elevation by2Ddiscrete element software.4)The qualitative analysis and quantitative calculation of unstable rockmassstability of the evaluation forecast results consistent, that is, unstable rockmassⅠandunstable rockmassⅣ stable in good condition,Generally,it does not occur the overallinstability, but unstable rockmassⅡ and unstable rockmassⅢ will produce localizeddamage even the overall instability of the adverse effects of the earthquake.5)Using the rockfall kinematics calculation theory to calculate the characteristicsof rockfall movement in the study area under own weight and strong earthquakeprojectile effect, the initial motion, the collision process and the slope movement threestages of movement along four typical profiles:①The rockfall and slope collide madeits motion features abrupt changes,because of slope overall moderate,and rockfallmovement speed and jumping height gradual decay,and the movement patternchanged from jumping into rolling until it stops;②The Gentle slope platform play agood cushioning effect to reduce the rockfall movement speed and jumping height;③The rockfall is mainly to stop the plot from the cliff foot10m to140m range,in linewith the results of field investigation;④The rockfall under strong earthquakeprojectile at the beginning projectile Motion for oblique,the speed experience theprocess of change decreases and then increases,compared with its own weight, therockfall speed and jumping height are larger in the same slope,and movement distanceis much longer.Selecting the trajectory2as a typical profile, using rockfall risk statistical analysis software,make Simulation analysis on the movement features of rockfalleffected by own weight and strong earthquake projectile,in order to make simulatemotion characteristics closer to the actual,dynamically select parameters within the setrange of calculation parameters, simulation results are basically in line with thekinematic calculation.