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| Face stability analysis of the circular tunnels in fractured rock masses based on the nonlinear Hoek-Brown failure criterion |
| SHI Xin1，ZHAO Dajun1，SONG Shengyuan1，ZHANG Zengzeng1，LIU Xuebo2，ZHOU Yu1 |
| (1. College of Construction Engineering，Jilin University，Changchun，Jilin 130026，China；
2. Beijing Urban Construction Design and Development Group Co.，Limited，Beijing 100037，China) |
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Abstract The face stability analysis of circular tunnels in fractured rock masses is a hot issue with important scientific value and practical significance. Due to nonlinear characteristics，the strength envelopes of fractured rock masses are often expressed with various different nonlinear failure criteria. Among the nonlinear failure criteria，the Hoek-Brown failure criterion is considered to reasonably model the strength of fractured rock masses. First，two existing failure mechanisms，the popular multi-block failure mechanism and modified multi-block failure mechanism，are modified and extended to calculate the limit support pressures of tunnel face in fractured rock masses within the framework of limit analysis theory. Second，the limit support pressures obtained from the two failure mechanisms and the two existing approaches，single cone failure mechanism and horn failure mechanism，are compared，which indicates that the results obtained from multi-block failure mechanism are between the results from the two existing approaches and the results obtained from modified multi-block failure mechanism are the best results when comparing with the other three failure mechanisms. Those influence rules are consistent with the rules of face stability analysis of circular tunnels in soils that follow the Mohr-Coulomb criterion. Finally，the limit support pressures obtained from the new failure mechanisms and other existing numerical simulations are compared. The results show that the results obtained from the two failure mechanisms in this paper provide consistent results with numerical simulations，especially for the results obtained from modified multi-block failure mechanism.
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2020, Vol. 39 
