Rock Classification for Tunnels in High Geostress Areas
(1 China University of Geosciences (Wuhan), Wuhan 430074; 2 State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou730000)
Abstract：
Surrounding rock classification is key for guiding tunnel construction, and its effect on tunnel construction in high geostress areas is fairly significant. Firstly, the influences of the lateral pressure coefficient of the geostress and the included angle between the maximum horizontal principle stress orientation and the tunnel axis on the classification of tunnel surrounding rock are presented in this paper; secondly, the geostress is corrected by increasing the included angle between the maximum principle stress orientation and the tunnel axis; and lastly, based on the Code for Design of Road Tunnels, the sub-classification is supplemented regarding rock masses of grades III, IV and V to achieve a more precise classification of tunnel surrounding rock. Using the Dapingshan tunnel on the Guzhu highway as an example, the surrounding rock classification is corrected by means of increasing the magnitude and orientation of the geostress, with results that are consistent with those of practical excavation.
2015, Vol. 52 