Research On The Rockfall Mechanism And Risk Assessment Methods On High-steep Slope In Subhorizontal Strata

The rockfall of high-steep slopes with subhorizontal strata is sudden and unpredictable,which have a significant impact on the safety of life and property such as roads,vehicles and local residents.For this type of interbedded slope,the mechanism of rockfall is that external forces intensify the weathering of mudstone,the continuous development of sandstone joints,the disintegration of the mudstone layer during the concentrated rainfall period,the development of the internal joints of the impending sandstone,and the rockfall of the isolated rock mass.This paper aiming at the rockfall disaster of subhorizontal strata high-steep slopes,studies five aspects of rockfall mechanism,slope stability analysis,disaster-causing body hazard,disaster-affected body vulnerability,rockfall risk level and puts forward corresponding theories and methods.(1)Establish the stability evaluation standard of rock slope and obtain the stability safety factor.A combination of qualitative method(stereographic projection)and quantitative method(numerical modeling)is used to analyze the stability of the slope.(2)Establishing a system to evaluate the disaster-causing body hazard.Selecting and quantifying assessment indicators and determining the weight of the indicators by the analytic hierarchy process.In the end,using the fuzzy comprehensive evaluation method based on the membership function to evaluate the hazard.According to the evaluation results,the risk level is divided into four levels.(3)Establishing a vulnerability evaluation system for the disaster-affected body of a rockfall disaster and selecting the main disaster-suffering object including roads,vehicles,and people.The road vulnerability is calculated based on the impact force of falling rocks and the ultimate bearing capacity of the subgrade based on the impact force.The calculation of vehicle vulnerability is based on the probability of traffic time and space.Human vulnerability is calculated based on the age structure and education level of the local residents.Calculating three type of vulnerability by the method of weighted mean to obtain the vulnerability level of disaster-affected body.(4)Establishing the standard of risk level assessment.The risk level of slope rockfall is obtained based on the disaster-causing body hazard and disaster-affected body vulnerability.Risk level provides theoretical basis for slope treatment decision.(5)Taking the high and steep slope at K44+200 of the Shenpan highway of G337 section as the supporting project,.Analysing the slope by the qualitative method and the quantitative method and the results obtained is corresponding to the actual situation.Evaluating the rockfall hazard and vulnerability to obtain the results that the slope is of high hazard and medium vulnerability.The slope risk level is Ⅲ,which is high risk and needs treatment timely.