| Jiuzhai Val ey was severely affected by the "8.8" earthquake,and the formation of multiple geological disaster points threatened the security of the scenic area and the progress of restoration and reconstruction.In this paper,based on the engineering example of the Panda Lake high-altitude unstable rock in Jiuzhai Val ey,grasps the geological environme nt conditions of the development of unstable rocks,and through the filed investigations and physical model test to analyzes the spatial distribution and the characteristics of deformatio n and failure of unstable rocks,and calculates the stable state of the unstable rock mass and the motion characteristic parameters of the fal ing rock,combined with the site situation of the unstable rock in the Panda Lake,putting forward targeted treatment measures.The main research results are as follows:(1)Unstale rocks is located at the right bank slope of the Panda Lake and aligned northsouth.The exposed bedrock is dolomite limestone,and the slope structure is reverse slope.The whole unstable rock area is divided into 4 dangerous rock zones and 7 typical unstable rock masses,and the rock stability mainly affected by three sets of structural surfaces.The unstable rock major failure modes are sliding,toppling and falling.(2)The results of unstable rock stability analysis show that all unstable rock masses are stable state under natural conditions,and the unstable rock has good stability;however,under rainy and seismic conditions,many unstable rock masses are under-stable or basic-stable,the unstable rock having more possibility of collapse.(3)Analyzing the deformation and failure modes of the unstable rock: Because the conclinal-dipped joint and the anti-dipped joint cuting each other,the rock mass is cut into blocks and sheets of different sizes.Some slope is uneven after rock masses collapsed,and which aggravates the weathering process.Due to the influence of external factors such as rainfall and earthquakes,joint plane gradually extended,resulting in unstable rock masses failure.Using the simulation software(UDEC)to simulate the deformation and failure process of typical unstable rock mass,and to verify the analysis conclusion of the deformation and failure mode.(4)The empirical formula calculation and Roc Fall software are used to calculate the kinematic characteristic of rockfall,which are collapsef from slope.The results show that the impact energy and bounce height of the rockfall are large,which poses a serious threat to the scenic road at slope foot and the Panda Lake.(5)Through the rockfall impact force model test,explore the relationship between rockfall impact force and the weight of the rockfall,the movement speed,the thickness of the buffer layer and other influencing factors,and put forward the empirical formula of the rockfall impact force.Which is compared the calculation results of rockfall impact force computed with other impact force calculation formulas,and provide a basis for the design of prevention measures.(6)According to the development characteristics of unstable rocks and the actual topography on the site,combined with the relationship between the unstable rock masses and the scenic road,a targeted prevention and control scheme is put forward.The scheme is as fol ows: adopt the “clearance + anchor rod + opening curtain net” to protect the upper unstable rock zone,and construct the pile-plank rock retaining wall at slope foot,and supporting landscape restoration project. |
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