Study On Sensitivity Of High Slope Dangerous Rock Mass Of Wanjiazhai Water Control Project

Dangerous rock mass refers to the rock mass and its combination which are cut by multiple rock mass structural planes and located on steep cliffs or slopes with poor stability.When the dangerous rock mass is affected by external induced factors,it will lead to the loosening and collapse of the rock mass,and finally the collapse.Wanjiazhai Water conservancy project is a water conservancy project of strategic significance in the Yellow River Basin of China.The dangerous rock mass and local collapse on the left and right sides of the road slope seriously affect the normal production activities in the dam area.In order to avoid or reduce the further loss of life and property in the dam area,this paper takes the dangerous rock mass of high slope on both banks of Wanjiazhai Water conservancy project as the research object,and studies the sensitivity of different types of dangerous rock mass.The main research contents and results are as follows:(1)According to the field survey,97 dangerous rock masses are found in 4 slopes on the left and right banks,all of which are small ones.According to the failure mode,the dangerous rock mass is divided into three types: sliding type,falling type and dumping type,of which 22 are sliding type,accounting for 22.7%;48 are falling type,accounting for 49.5%;27 are dumping type,accounting for 27.8%.(2)According to the characteristics of high slope dangerous rock mass,eight sensitive factors are selected to establish the evaluation index system,including dangerous rock density,weathering degree,cohesion,internal friction angle,earthquake action,maximum crack width,dangerous rock self weight and crack length,and sensitivity analysis is carried out for dangerous rock mass with different failure modes.After calculation,the weight of each sensitive factor is obtained,and the results from large to small are as follows:Sliding dangerous rock mass: dangerous rock density 0.291,weathering degree 0.273,dead weight 0.162,fracture length 0.100,internal friction angle 0.075,cohesion 0.046,maximum fracture width 0.031,seismic intensity 0.021.Falling dangerous rock mass: weathering degree is 0.298,dangerous rock density is 0.285,dangerous rock self weight is 0.147,fracture length is 0.103,cohesion is 0.075,internal friction angle is 0.050,maximum fracture width is 0.030,and seismic intensity is 0.022.Dumping dangerous rock body: fracture length 0.331,dangerous rock self weight 0.247,dangerous rock density 0.141,weathering degree 0.107,internal friction angle 0.076,cohesion 0.044,maximum fracture width 0.031,seismic intensity 0.024.(3)In this paper,FLAC3 D,a finite element software,is used to simulate and analyze the typical dangerous rock mass with three failure modes: sliding mode,falling mode and dumping mode.The results show that under natural conditions,the maximum displacement and stress distribution of the three failure modes are basically consistent with the actual situation in the field.(4)Nine groups of models are established respectively,and the maximum displacement under nine groups of models is obtained by FLAC3 D numerical simulation,The grey correlation method is used to calculate the correlation degree of each influencing factor,so as to quantitatively analyze the influence degree of each influencing factor on the dangerous rock mass.After calculation,the results of correlation degree from large to small are as follows:Slip type: dangerous rock density > dangerous rock self weight > dangerous rock fracture length > internal friction angle > Poisson's ratio > elastic modulus > cohesion > maximum fracture width.Falling type: dangerous rock density > dangerous rock self weight > Poisson's ratio > dangerous rock fracture length > cohesion > elastic modulus > internal friction angle > maximum fracture width.Dumping type: crack length > dead weight of dangerous rock > density of dangerous rock > elastic modulus > internal friction angle > Poisson's ratio > cohesion > maximum crack width.Under the three failure modes,the calculation results of correlation degree of influencing factors are basically consistent with the weight calculation results,so it can be considered that the research method is reasonable and effective for the dangerous rock mass of the three failure modes in this area.