Rock Mass Quality Classification of Wudang Group Schist Based on a Corrected Q-Value

Rock masses with special geological backgrounds are often encountered during construction of under? ground works, and it is necessary to establish a corresponding rock mass quality classification method. In light of the features and weak points of Q-value classification, the characteristics of water sensitivity, anisotropism, unsymmetrical structure pressure and the horizontal tectonic stress of a structure are analyzed using the Wudang group schist in northwest Hubei province as an example. A corrected Q- value classification is presented considering rock mass strength, rock integrity, groundwater, geostress and occurrence of schistosity plane, and a calculation formula for Qvalue classification, which takes ground water (exposure condition and water pressure), geostress (magnitude and included angle with excavation axis) and schistosity obliquity as correction factors, is obtained. An analytical validation is conducted based on the Tongsheng tunnel on the Shiyan-Fangxian expressway, and results are consistent with the actual rock quality classification.