| The project area of a hydropower station in the upper reaches of Lancang River has the characteristics of deep valley, strong unloading rocks, frequent earthquake, high geostress, circles of freezing and thawing of rocks and heavy weathering. There are many cataclastic loose rock mass zones with a wide range and a deep depth in the dam area, which has a serious impact on the stability of the slope. Therefore, it has great significance to find out the reasons and the characters of fractured rock mass and evaluate and predict the stability of the slope to late construction and operational support of the hydropower station.Through the detailed field geological survey of geological conditions, development characteristics, deformation characteristics of rock mass structure, signs of deformation and destruction of the cataclastic loose rock mass, the deformation and failure mode of the cataclastic loose rock mass in the downstream of the right bank of the dam. On the basis of qualitative evaluation, the stability of main cataclastic loose rock mass slope in the downstream of the right bank of the dam is calculated by using rigid limit equilibrium method combined with numerical simulation referencing the parameters of cataclastic loose rock mass obtained by experiment. The specific content and results are as follows:(1)Cataclastic loose rock mass is defined as having a fractured and each structure surfaces are open. The rock mass of dam area is divided into four types: extremely strong unloading belt, strong unloading belt, weak unloading belt and new rock, Cataclastic loose rock mass develops in all of the extremely strong unloading belt and a small part of the strong unloading belt, the test showed a low sonic velocity, each structure surfaces of the rock are open, its permeability is strong, its quality is poor.(2) Combined with the field geological survey and unmanned aerial vehicle(uav) to identify the areas of cataclastic loose rock mass accurately, detailed investigation on cataclastic loose rock mass' s development scale, rock mass structure characteristics and the deformation and fracture characteristics in slope table and adit.(3) On the basis of investigation to the rock mass structure and the deformation and fracture characteristics in slope table and adit, summarized cataclastic loose rock mass deformation and failure mode, mainly for toppling damage, the plane sliding ladder sliding wedge slide, accumulation unstable modes.(4) Classify the rock mass of dam site area to different engineering geology categories with the engineering analogy method. Four categories as II,III,IV,V could be divided, and IV,V could be divided into two classes, loose cataclastic rock mass is defined as V2.(5) Using uniaxial, triaxial tests obtained the mechanical parameters of dacite, combined with field distortion test, field large shear test obtained the mechanical parameters of rock mass, finally combined engineering analogy and the relevant literature PARAMETERS got mechanics parameters of all kinds of rock and structure surface, especially the parameter values of cataclastic loose rock mass.(6) The stability of cataclastic loose rock mass slope as 2#, 4#, 6#, 8#, and 10# seated on the right bank of dam site would be evaluated by method of qualitative evaluation. The results indicate that its overall basic stability under natural conditions, unstable state under heavy rain conditions and in a state of flux under both of earthquake, storm conditions, respectively. The stability of different controlled structural plane for tailrace tunnel and the loose cataclastic rock mass slope as 12#, 14#, 16# nearby tailrace tunnel would be calculated under three kinds of conditions with rigid body limit equilibrium method.(7) Using the discrete element UDEC numerical simulation to analyse cataclastic loose rock mass slope of the tailrace tunnel, simulated conditions of the three failure modes, obtained under native condition in a substantially stable state; in storm conditions, cataclastic loose rock mass broken from the bottom, the upper portion of cataclastic loose rock mass further damage; in earthquake conditions, cataclastic loose rock mass vibration slack then overall damaged.(8) Using the discrete element 3DEC numerical simulation to analyse the startup sequence and failure process destroys three cataclastic loose rock mass in storm conditions, obtained 14 # first started. |
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