| Collapse and rolling rock disasters are one of the most common types of geological disasters and dynamic landforms in the mountainous areas of western China,which are characterized by sudden occurring and destructive force.Due to the impact of the 8.8Jiuzhaigou earthquake on the right bank slope of the upstream of the Panda Lake in Jiuzhaigou Scenic Area,Large-scale avalanche occurred in loose rock soil and joint fractured rock mass.At the same time,the strong vibration severely damaged the integrity of the slope body,and the rock body was more broken.If it is not treated in time,it will seriously affect the post-disaster recovery and reconstruction work of Jiuzhaigou Scenic Spot and threaten the safety of the lives and property of tourists.In this paper,through detailed field investigations,the development location,scale and possible instability model of the dangerous rock were comprehensively investigated.For the dangerous rocks existing on the slope of the study area,the stability coefficient based on the rigid body limit equilibrium theory were calculated.And while the dangerous rock collapse,the kinematics characteristic values such as the bounce height,impact energy,movement speed were also calculated.Finally,combined with the management requirements of Jiuzhaigou Scenic Area,the ecological treatment measures were proposed.The main contents are as follows:(1).According to detailed field geological surveys,the right bank slope of the upstream of the Panda Lake in Jiuzhaigou Scenic Area can be divided into three dangerous rock belts and six dangerous rock bodies,and their spatial distribution characteristics and development scales are described in detail.The main controlling factors for the development of dangerous rocks in the study area include topography,stratigraphic lithology,rock mass structure,rainfall and earthquake.(2).The instability mode of dangerous rocks in the study area is mainly slippling,and WY5-the dangerous rock-it's stability in the study area under different working conditions is simulated using the discrete element program(UDEC).The conclusion demonstrates that the dangerous rock is stable under natural conditions;a small amount of falling rocks and blocks will occur near the upper free surface and the central concave rock cavity under heavy rain conditions,but the whole is still in a stable state;however,under the action of an earthquake,the upper fracture and the lower shear of the potential rupture area jointly form a through fracture surface and the whole is unstable.(3).The empirical formula and Rocfall software were used to calculate and simulate the kinematic characteristics of falling stones in the dangerous rock zone on the right bank of the upper panda lake in Jiuzhaigou Scenic Area,the results of the study show that the falling stones may be harmful to the highway which is at the slope foot.(4).Jiuzhaigou Scenic Area is a world natural heritage and a national-level nature reserve in China.The prevention and control of geological disasters must establish a complete prevention and control system,and at the same time do a good job of regional geological research,implement ecological governance,and achieve sustainable regional development.Combined with the experience of ecological prevention and control of rock slopes at home and abroad,it is recommended to use anchor rods +covered curtain nets for the reinforcement of dangerous single rock slopes,set up sheds at the foot of the slope to block falling rocks,and supplement vegetation protection. |
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