| In recent years,with the rapid development of urban construction,the geological environment has deteriorated,human engineering activities have increased,and the resulting geological disasters have also increased rapidly,especially the disasters caused by the collspse of perilous rocks are frequent,the instability of perilous rock has high suddenness and strong destructiveness,especially collapse caused by earthquakes is often destructive.There are many forming factors and failure modes of perilous rocks,and the movement forms and trajectories of perilous rocks are complex,it is difficult to predict,tough to control,and will result in enormous losses to people.Perilous rocks in Zijin Mountain are not only located in Himalayan seismic belt,but also belongs to the alpine region,with frequent earthquakes and strong tectonic movement,which has caused great harm to the lives and property of local people.Therefore,the study of the perilous rocks in Zijin Mountain not only can effectively control the collapse of perilous rocks in this area,but also has reference significance for the prevention of collapse in other areas under the same environment.This paper,based on the project of ?Study on the Generation Regularity and Prevention of Geologic Hazards in the Himalayas Seismic Belt(Xigaze region)?,takes the Zijin Mountain perilous rocks of Tibet as the research object.collecting the date of geological environment conditions in the study area,and investigation on the basic features of perilous rocks.Establishing and generalizing rock slope model with joints and though shaking table tests to study the formation mechanism and failure mode of perilous rocks in alpine earthquake zone.The numerical simulation software is used to study rockfall and collapse two types? motion characteristics in the study area,the researches have certain reference value for disaster provention and engineering management.The following conclusions are drawn from this study.(1)The formation of perilous rocks is influenced by many factors,such as topography,lithology,intercombination of structure,freezing and thawing,earthquake and so on.Perilous rocks of Zijin Mountain are located in alpine and high altitude area of Tibet,it is obvious of freezing-thawing effect with sparse vegetation,large temperature difference between day and night.There are some differences in the forming conditions between collapse and rockfall.(2)Investigating and analysing the development characteristics of joints and the combination of structure in different perilous rock belts,and combined with the research of predecessors,the potential failure modes of the perilous rock belts in the study area are obtained: the perilous rock belt 1 is type press shear-slip,the perilous rock belt 2 is type split-dump,the perilous rock belt 3 is type falling.(3)In order to study the failure feature of collapse in alpine,high altitude and high seismic intensity region under earthquake.Shaking table tests are carried out on four rock slope models: freeze-thaw bedding slope,normal bedding slope,freeze-thaw reverse slope and normal reverse slope.According to the test results,it can be concluded that:(1)The horizontal and vertical acceleration responses of the four slope models show the amplification effect on the elevation,and the slope deformation and destruction started at the top and the surface of slope.(2)Among the four types of slope,the freeze-thaw bedding slope is the first to be destroyed,followed by the normal bedding slope,the freeze-thaw reverse slope and normal reverse slope.The freeze-thaw has impact on the stability of the slope.(3)The deformation and destruction of the bedding slope is divided into three stages: surface loosening,crack propagation and entire slipping.The failure mode can be summarized as earthquake induced—top loose and drop,crack formation—crack extension—entire slipping.(4)The deformation and destruction of the reverse slope is divided into three stages: top loosening dislocation between layers,crack development expansion and toppling.The failure mode can be summarized as earthquake induced—top loose and drop,dislocation between layers—crack extension—entire toppling and surface rock shattering—throwing and falling.The test results are consistent with the results of the local geological survey.(4)Combined with the results of field investigation and analysis,the Rocfall software is used to simulate the motion characteristics of the perilous rock belt 1(type rockfall),and the characteristics of rockfall accumulation,motion trajectory and the changes of bounce height,velocity and kinetic energy were obtained.Taking the perilous rock belt 2(type collapse)as the object to study motion characteristics.Using PFC3 D software to explore the motion process,trajectory,velocity and accumulation characteristics of collapse.The results are well fitted to the field analysis. |
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