Forecast Of The Spatial Of Discontinuities In Large Scale Underground Caverns And Its Application

Owing to complexity and hidden nature of the subsurface geological conditions, deep geological conditions investigations are extremely difficult in underground engineering. Particularly in surrounding rock stability and the discontinuities distribution characteristics of underground caverns that is large scale and complexity in spatial arrangement. Based on the limited and discrete geological data in the project early, the spatial distribution characteristics of discontinuities, and the surrounding rock stability of large scale underground caverns that will excavate in the future, are forecasted, which possesses enormous significance to plant sitting, design and post-operation.Here takes the underground powerhouse of Laxiwa hydropower project for research object, based on geomechanics, discontinuities statistical laws and the geological data which is revealed by the exploration adits, the discontinuities spatial distribution characteristics and local surrounding rock stability of the underground powerhouse were forecasted. The main research contents and conclusion are as follows:(1) Detailed analysis of the engineering geological conditions and underground powerhouse of the dam area in Laxiwa hydropower station, such as formation lithology, geological structure, topography and geomorphology, hydrogeology, physical geological appearance, new tectonic activities and earthquakes, etc.(2) According to the sitting selection principle of underground cavern, the criterion for axis direction selection of the main cavern is analyzed through the aspect of geostress and discontinuities. The result is that the maximum geostress direction is nearly SN, axis direction of the three principal caverns is NE25°, and the separation angle between caverns axis direction and maximum geostress direction is less than30°.(3) Analyses of the discontinuities characteristics of stulm in powerhouse zone. based on the geomechanics theory, statistical laws of discontinuities and the geological information revealed by the exploration adits, the spatial distribution characteristics of large scale underground caverns that will excavate in the future, are forecasted, by using the relationship between length and width of the discontinuities, spatial distribution theory, and the discontinuity network modeling. It shows that the forecast consequence compared with the result of the forecast and real discontinuities in underground caverns well.(4) Base on discontinuities predict results and block stability theory, forecasting the local surrounding rock stability. The result indicates that the forecasting block number is close to the practical quantity in the underground caverns, and further illuminates the forecasted result of the discontinuities distribution characteristics are extremely reliable.