Probabilistic analysis of three-dimensional tunnel face stability in soft rock masses using Hoek–Brown failure criterion |
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| Authors: | Jiahua Zhang Lianyang Zhang Weijun Wang Daobing Zhang Biao Zhang |
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| Institution: | 1. Work Safety Key Lab on Prevention and Control of Gas and Roof Disasters for Southern Coal Mines, Hunan Provincial Key Laboratory of Safe Mining Techniques of Coal Mines, Hunan University of Science and Technology, Xiangtan, 411201 China;2. Department of Civil and Architectural Engineering and Mechanics, University of Arizona, Tucson, Arizona, 85721 U.S.A.;3. School of Civil Engineering, Central South University, Changsha, 410075 China |
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| Abstract: | This paper investigates tunnel face stability in soft rock masses via coupled limit and reliability analyses. Specifically, a 3D face collapse mechanism was first constructed. Then the Hoek–Brown failure criterion was introduced into the limit analysis via the tangential technique. Taking the variability of rock mass parameters and loads into consideration, a reliability model was established. The collapse pressure and failure range of tunnel faces were determined. In addition, the required factor of safety (FS) and supporting pressure under three safety levels were obtained, and the corresponding safety level graphs for support design were presented. Comparison of the obtained results with previous work demonstrates the rationality of the 3D collapse mechanism and the validity of the results. A decrease in the geological strength index, Hoek–Brown parameter mi, and uniaxial compressive strength or an increase in the disturbance factor results in a nonlinear increase of the collapse pressure and an enlargement of the failure zone. Such changes also lead to a nonlinear increase of the required support pressure under a certain safety level. By contrast, the FS does not exhibit any obvious change when these parameters vary. Therefore, when a rock mass is of poor quality or heavily disturbed, the advance support should be enlarged from upper front to right above the tunnel face. Moreover, as the safety level increases, both the required FS and supporting pressure of the tunnel face increase nonlinearly at a higher rate. |
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| Keywords: | failure probability Hoek–Brown failure criterion limit analysis support pressure three-dimensional collapse tunnel face |
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