The Characteristics And Risk Analysis Of Rockfal Disasters Along The Roads In Baishui River Basin

Baishuijiang river basin is located in the transitional zone of Qinghai Tibet Plateau,Loess Plateau and Sichuan Basin.It has complex topography,strong tectonic activity,large vertical drop,significant River undercutting and high occurrence of collapse and rockfall disasters,which has a significant impact on road safety operation and human activities.Therefore,the study on the development and distribution characteristics of rockfall along the roads in Baishui River Basin,the zoning of rockfall susceptibility and the calculation of the risk level of roads and vehicles affected by rockfall can provide theoretical basis and reference for the road safety operation,disaster prevention and mitigation engineering and road planning in the study area.In this paper,through field investigation,remote sensing interpretation and other means to determine the rockfall disaster information in the study area,extract and analyze 15 external and internal factors such as elevation,slope,aspect,road distance and seismic peak acceleration.Three models of information model(I),logistic regression model(LR)and information quantity logistic regression model(I-LR)were constructed to carry out rockfall hazard susceptibility analysis,rationality and accuracy test,and draw rockfall hazard risk zoning map in the study area;Based on GIS and Rockyfor3d software,the 3D kinematics simulation of rockfall disaster along the road in the study area was carried out;Quantitative risk assessment(QRA)method was used to quantitatively assess the impact of rockfall on roads and vehicles in the study area;The effects of different resolution digital elevation models(DEM)on the analysis of rockfall disaster characteristics and the simulation results of movement characteristics are analyzed.(1)Based on field investigation and remote sensing interpretation,367 rockfall disasters were obtained,covering an area of 9.43km~2,accounting for 0.65%of the total area of the study area;According to the distribution location and genetic type,the rockfall along the road in the study area can be divided into cut slope rockfall and high-level rockfall.(2)Extraction and analysis of impact factors of rockfall along roads in Baishuijiang River Basin.Based on 15 kinds of influence factors,the distribution law of rockfall disaster is analyzed and analyzed according to the actual contribution and frequency ratio method.Rockfall disasters are mainly distributed in the low elevation area of 648～1448m,Southeast,South and southwest sunny slope area,30～50°Slope region,curvature region of-1～0 and 0～1;449～1049m topographic relief area,1.1～1.5 surface roughness area,92～392m surface cutting depth,0.09～0.21 height variation coefficient area,zhagashan group,Bikou Group and Heihe formation three lithology areas,0～500m and>4000m fault distance area,490～550mm rainfall area,0.15g seismic peak acceleration area,forest land use type,0.1～0.2 vegetation coverage index area,<400m road distance area.(3)The construction and accuracy test of the evaluation model of rockfall vulnerability along the road.In this paper,I,LR and I-LR models are constructed,combined with the application of GIS and SPSS software,to analyze the susceptibility of rockfall along the road in Baishuijiang River Basin.The area under the ROC curve for the accuracy of the three models is 0.857,0.836,and 0.860,respectively,and the I-LR model is considered to have the highest accuracy.(4)Evaluation and grade division of rockfall hazard susceptibility.The area of rockfall disaster prone area is 140.56km~2,accounting for about 9.76%;The area of high risk area is136.75km~2,accounting for about 9.50%;189.58km~2,accounting for about 13.17%;The area of low incidence area is 436.12km~2,accounting for about 30.29%;The area of extremely low risk area is 536.93km~2,accounting for about 37.29%.(5)Three dimensional simulation of rockfall movement characteristics and quantitative calculation of rockfall risk.The movement characteristics of rockfall,such as the number of road blocks,jumping height,maximum speed and energy,are obtained,and the road and vehicle risk(QRA)is calculated quantitatively.20%of the simulated rockfall can reach the road,one very high(VH)road rockfall risk is developed along the line,accounting for 0.33%,and 46 high(H)rockfall risks,accounting for 15.13%;There were 59 middle risk(M),accounting for 19.41%.The UA risk of vehicles encountering rockfall is 13.89km,accounting for 3.93%.There are 76 unacceptable(UA)risks above 50m that should be paid special attention to in the long-term.(6)Comparative analysis of simulation results of rockfall movement with different resolution digital elevation models(DEM).High resolution DEM is obtained by using photoscan modeling,and the influence of different resolution(1m,5m,12.5m)DEM on rockfall source identification and rockfall movement process simulation results is analyzed.