| Dangerous rock is one of the common geological hidden dangers in mountain and canyon areas.In recent years,the "one belt,one road" strategy has been applied in China.Human engineering activities have been gradually advancing to the mountainous areas,and induced by extreme weather conditions.The frequency of collapse disaster in mountain area is increasing,which seriously threatens the safety of life and property of local residents.It has become a key engineering technology issue of great concern for relevant departments to correctly evaluate the stability of dangerous rock and put forward reasonable prevention and control measures.Because of the complex geological environment in mountain area,how to obtain the geological disaster information quickly and accurately has always been the difficulty in the study of dangerous rock.In this paper,taking the collapse in Zhaizi village,Kaiyang County,Guizhou Province as the research object,the UAV photogrammetry technology is applied to the investigation of high and steep slope dangerous rock in the mountain area.According to the results of investigation and statistics,the development and distribution law and damage characteristics of dangerous rock in the research area are summarized.The three-dimensional movement characteristics of dangerous rock are studied by numerical simulation method.Based on the hazard model and vulnerability model of the collapse disaster,the risk assessment of the collapse disaster in the study area is carried out,which provides technical support for the formulation of economic and effective prevention and control scheme of the collapse disaster in the mountain area.The main research results are as follows:(1)A detailed aerial survey of dangerous rocks in the study area was carried out by UAV.The three-dimensional real scene model is constructed to accurately identify the geometric characteristics,spatial location and instability mode of the dangerous rock,thus realizing the rapid identification of the dangerous rock.According to the existing deformation and failure characteristics and development of the collapse zone in the study area,the dangerous rock in the area are classified in detail.Based on the three-dimensional point cloud model,a fast measurement method for the occurrence of structural plane of rock mass in high and steep slopes is proposed,and the terrain modeling method for rapid acquisition of numerical calculation is summarized.the technical process of UAV remote sensing in the investigation of high and steep slope dangerous rock in mountain area is established.(2)Based on the survey and statistical results of the dangerous rock in the study area,the development and distribution law of the dangerous rock is summarized: the dangerous rock is mainly medium-sized,mainly belongs to high and extra high dangerous rock,and the dangerous rock development is mainly controlled by the slope structure.According to the instability model of dangerous rock,the dangerous rock in the study area can be divided into five types,namely,tension crack-collapse type,tension crack-toppling type,tension crack-falling type,tension crack-staggering type and rolling type.According to the characteristics of structural plane of rock mass,this paper analyzes the failure characteristics of dangerous rock caving,and concludes that the failure mode of dangerous rock caving is mainly the disintegration of the upper rock mass along the structural plane.By analyzing the influencing factors of the stability of dangerous rock,it is concluded that underground mining and rainfall are the main factors that lead to the collapse disaster.(3)Based on the spatial analysis ability of Arc GIS platform,rockfall analysis software is used to simulate the three-dimensional movement characteristics of rockfall,analyze the three-dimensional movement track characteristics of rockfall,and evaluate the risk of rockfall disaster according to the spatial grid distribution characteristics of key factors such as rockfall frequency,rockfall bounce height and rockfall motion energy.The results show that W7,BT2#,W10,BT3#,BT6#,W23,LS14 and other dangerous rocks are high hazard.The maximum distance of rockfall is 452 m,which directly threatens 60 people and the potential economic loss is more than 3 million yuan.(4)According to the characteristics of the collapse disaster in the study area,the method of three-level evaluation factor classification is proposed.Four evaluation factors are selected as the first level indexes,including geometric characteristics,rock and soil characteristics,disaster body status and induced factors.Ten evaluation factors are selected as the second level indexes,including slope height,slope gradient,potential instability volume,slope structure,controlled structural plane inclination,rock structure,surface deformation strength,deformation stage,human engineering activities and rainfall.The hazard assessment index system of collapse disaster is established.The weight of the three evaluation factors is determined by RES method,and the hazard of collapse disaster is constructed.The hazard of dangerous rock in the study area is evaluated.The results show that the dangerous rocks in the study area are mainly high hazard and medium hazard.(5)The vulnerability of disaster bearing body is evaluated by introducing the exposure index.According to the statistics of the probability of arrival of the collapse disaster,0.5 and 0.2 are selected as the boundary points,and the corresponding minimum arrival angles are 37 ° and 24 ° respectively.The exposed area of the disaster bearing body is divided into three levels: high exposed area(1?0.5),medium exposed area(0.5?0.2)and low exposed area(0.2?0).The vulnerability evaluation model is constructed.Based on the hazard model and vulnerability model,the risk assessment model is constructed,and the risk assessment of collapse disaster in the study area is carried out.The results show that BT6#,BT2#,W23,W10,LS10,W15,BT3-?,W21,LS15 are of high risk. |
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