Research On The Mechanism Of Slab-rent Rock Mass And Slope Stability

The concept ofslab-rent rock mass was put forward by Sun Guangzhong,scholars such as Ni Guorong,Zhang Wenbin,Pan Ruilin has researched on basic theory and experimental study of that rock structure.Slab-rent rock mass looks like slate,it generated bytectogenesis and hypergenesis.After structural transformation,the engineering properties of rock-mass is different from the previous status.Most scholars focus on the engineering properties of slab-rent structure,in-depth study of the mechanism and process is lacked.This dissertation,based on Jinchuan open-pit mine rock slope,the left bank slope of LancangRiverXiaowan hydropower Station and quarry slope of Pubugou hydropower,summarizes the mechanism of slab-rent.Takebank slope in front of one hydropower station at the yellow river for example,and research on characteristic of bank slope deformation,failure and its slab-rent structure rock mass.According to geological investigation,find out how slab-rent happened and affect slope stability.The main research results are as follows:(1)From the perspective ofstress differentiation,unloading rebound with the differences and dynamic-loadeffect,this dissertation analysis the mechanism of slab-rent rock mass.All sedimentary,igneousand metamorphic rocks can generate slab-rent structure.(2)The article analyses mechanical characteristics,through the typical failure modes of inverted-dip slope and consequent-dip slope,of the various stages.Get length-limit formula,(?),of consequent-dip slope.Derive formula to judge tensile failure and deflection of inverted-dip slope.Use UDEC to establish invert-dip and consequent-dip slope models by changing single factor.The invert-dip slope get worst stability,when slab-rent dip around 35°~45°;When the slab-rent dip is around 45°~55°,the consequent-dip slope is at worst status.When the thickness,strength of rock and slab-rent surface is weaken,the stabilities of both types will get down.(3)By considering the different combination of rock-crack and rock-bridge dip,use Continuum-based Discrete Element Method(CDEM)to simulate crack propagation modes and failure modes.The study found,in the process of loading,the cracks are central symmetrical;When the dip of main cracks changes between 0° and 45°,the new cracks are distributed in both main cracks and its top,and enriched to top with angle value increased;When the dip of main cracks increase from 45°to larger,the length of new cracks becomes shorter,and airfoil cracks begin togenerate in rock-bridge.The article study on failure-types of rock-bridge by keeping cracks' dip-angle in 30° and changing rock-bridge dip;The result shows that the development of cracks is manifested as purely shear failure,when the angle of cracks is set between 30° to 60°;When the dip of cracks excess 60° or more,the broken form include shear and tension broken,and high dip of rock-bridge tends to fail as surrounded form.The consequent isof great significance for finding how steeply dipping slab-rent rock mass structure of bank-slope generated.By single factor changed,build typical UDEC model,include inverted-dip slope and consequent-dip slope,to analysis how the factors affect the stability of slope;When the dip of slab-rent in the range of 35° to 45°,consequent-dip slope gets the worst stability;When 40° to 60°,the inverted-dip slope gets the worst safety.The two types of slab-rent slope's stability get weaken,when the thickness and strength of slab-rent structure reduced.(4)Throughsurveying on study area's bank-slope rock-mass structure,it shows that there exists two main groups of rock structure,nearly NE and SN direction,and they are shear failure surface and show as conjugate relationship.Study on valley stress evolution and its zonation by building CDEM and FLAC3 D computational model;The distribution characteristics of stress shows there exists stress reducing,increasing and unchanged zones.Combine stress zonation characteristics of bank slope and slab-rent process of typical NO.3 geological section to analysis the mechanism of slab-rent massive granite.As the valley cutting down,the primary joints turn into gently dipping structural surface;Then Steeply dipping structural surface occurs between gently ones.Finally,the massive granite is cut into slabs.(5)Combined with field surveys,consideringthe most dangerous combination of the slope and the fracture surfaceof the rock structure,use rigid body limit equilibrium method to evaluate the stability of the six most dangerous sliding combinations.Assessment results show,under dynamic loading and water slide disturbances,the shallow areas of bank slope are probably to slide.At last,the paper suggests that proposal clear shallow slope,drainage given closure,increased monitoring and inspections,active and passive protection in combination protect slope.