Evaluation of the Permeability of Rock Masses around the Equalized Room with Atmoseal at Ziyili Hydropower Station, Sichuan Province

Ziyili Hydropower Station in Sichuan Province uses an equalized room fitted with atmoseal, which needs a more precise investigation on the permeability of rock masses around the power house. This paper proposes an effective method that systematically characterizes the permeability of rock masses, from qualitative analyses to quantitative analyses. Based on a study of basic geology and hydrogeology conditions, we measured the geometric parameters of fractures (such as orientation, aperture, trace length, space and fracture frequency) and obtained their characteristic statistical values. We then calculated the main value and comprehensive value of the permeability tensor using permeability tensor theory, and finally divided the rock masses around the power house into a few permeability subareas. The general permeability of the rock masses around the power house varies with depth and the local permeability varies alternately between the higher and the lower due to the effect of the contact strip. The permeability can be divided into three grades. The permeability of rock masses near the surface is higher (n×10⁰ m/d~n×10^-1 m/d) and permeability of rock masses around the equalized room with atmoseal is moderate to lower (n×10^-2 m/d~n×10^-4 m/d).