Study On Alteration And The Stability Of Surrounding Rock Of Underground Caverns Under Influence Of Altered-rock In Tianchi Pumped-storage Station

The altered rock is the soft rock which is scarce in the engineering,The features ofalteration significantly affect the engineering geological characteristics, and thus influence thesafty of the dam and underground powerhouse. According to the data of Tianchipumped-storage station,There is altered rock formed under the action of hydrothermal fluidsin reservoir of this pumped-storage station,In order to understand the engineeringcharacteristics and the stability of surrounding rock in the underground powerhouse underinfluence of Altered-Rock completely. the mechanical property of the altered rock in Tianchipumped-storage station has been deeply and fully studied,Combining Macro with Microanalyzes method,geological survey,micro and mechanical testing has been carried out to studythe mineral composition,chemical composition,master the physical and mechanical properties,find out the type,cause and distribution, And then evaluate the engineering geologicalcharacteristics and distribution pattern of the altered rock in research area.The most tremendous influencing factors of the stability of underground powerhousesurrounding rock are obtained by formulating an orthogonal test program combining the testtheory and method, the factors are elasticity coefficient, cohesive force,angle of friction andthe poisson ratio, This has provided basis for the selection of parameters for the numericalsimulation and influence of various kinds of alteration on the surrounding rock stability isconcluded. Meanwhile, a3D dynamic calculation model for staged excavation ofunderground powerhouse is built using FLAC3D to compare the surrounding rockdeformation, stress and distribution of plastic zones under different calculation schemes.The results demonstrate that:There is altered rock formed under the action ofhydrothermal fluids in reservoir of Tianchi pumped-storage station,it distribute along therising channel of hydrothermal,Along with the alteration degree increase，porosities andexpansion of altered-Rock are increased,the densities are decreased, it has water-disintegrableproperties,the mechanical properties of altered-Rock are decreased,it has great influence onthe stress displacement field and plastic zone in the excavation of surrounding rock,influencethe stability of surrounding rock.