Study On The Rock Mass Structure Characteristic And Stability Of Tailrace Tunnel Vent Slope Of Nuozhadu Hydropower Station

The rock mass structure characteristic controls the mechanical property, characteristic of deformation and failure of rock mass, etc. It is becoming the basement of stability analysis of huge rock excavation slope to understand rock mass structure characteristic exactly. This thesis taken the tailrace tunnel vent slope of the Nuozhadu Hydropower Station on Lancang River of Yunnan province as an engineering example. The comprehensive complexity of integrity of topography, excavation shape, depth and geological techtonics of this slope is more sophisticated than any other rock slope. Based on a great deal of geological investigation documents of this slope, the thesis attaches most important things to the operation of rock mass structure, the deformation of rock mass and the mechanism of deformation corresponsive is researched while large and high rock slope is excavated. Then the stability of high rock slope after excavation is evaluated reasonable. Some major study methods, contents and some conclusions showed as following:1. Coupled with excavation of slope, the rock mass structure characteristic of tailrace tunnel vent slope is studied comprehensively, including the genetic analysis of different discontinuity, the engineering geological classification of discontinuity, the engineering geological characteristic of different discontinuity and the physical mechanics of rock mass, the mode of rock mass structure is established.2. Based on the deformation and failure indications of slope which discovered during excavation period, coupled with the rock mass structure characteristic, the mechanism of deformation and the mode of deformation being analyzed, the mode of deformation and failure is generalized.3. Applied two dimension finite element numerical simulation software to analyze stability of the three engineering geological cross sections of tailrace tunnel preliminary, and obtained some primary cognition for the alteration of secondary stress field and displacement field of different position of slope.4. Applied three dimension finite difference numerical simulation software to simulate the operation of rock mass structure of tailrace tunnel vent slope during exaction period, and the characteristic of class II discontinuity is considered especially. The conclusion indicates that the alteration of secondary stress field and displacement field of slope can conformity with the monitoring result badly.5. Calculating and assessing stability of block of tailrace tunnel vent slope that existing potential destabilization through the computer software, which based on the rigidness limit equilibrium theory. There are no potential hazardous block which will influence the global stability of slope excavation and project operation.