基于统计岩体力学的围岩分级调整以关山隧道为例

在浅埋工程开挖的围岩分级实践中，相关规范实用性很高，预测准确。然而，在大埋深高地应力条件下进行含节理岩体的隧道开挖时，围岩物理力学参数和结构会发生强烈的改变，不但围岩质量劣化，而且各向异性显著。在开挖引起的应力场剧烈变化下，围岩中新的裂隙会产生，在高地应力下闭合的结构面会重新张开并迅速发展，影响了岩体质量和稳定性，开挖前的围岩分级结果不再适用。因此，为了客观量化描述开挖后围岩质量的劣化，统计岩体力学理论充分考虑了开挖揭露的岩体结构面各项参数，并将结构面影响下的岩体各向异性特征纳入围岩分级评估之中进行围岩分级调整。为了进一步说明，本文结合大埋深高地应力下的关山隧道开挖工程，根据现场结构面的统计结果，运用统计岩体力学理论分析开挖后隧道围岩显著的各向异性，并最终给出符合开挖后现场围岩劣化情况的围岩分级调整建议。

ADJUSTMENT OF ROCK MASS CLASSIFICATION BASED ON STATISTIC MECHANICS OF ROCK MASS(SMRM)TAKING GUANSHAN RAILWAY TUNNEL AS EXAMPLE

Unlike well predicting by specification method on rock mass classification in shallow project before excavation, in the tunnel excavation of jointed rock mass in large depth and high in situ stress, there are great change of rock mass parameters and structure, revealing not only the degradation of rock mass quality also the significant anisotropy of rock mass. Because the micro fracture or closed rock structural plane under high in situ stress will re-open and develop quickly during stress field change due to the excavation, which affects the stability and quality of rock mass. The rock mass classification before excavation is not suitable anymore. Therefore, for the purpose of describing the degradation of rock mass quality after excavation objectively and quantitatively, SMRM takes into account the anisotropy of rock mass affected by structural plane in the rock mass classification, fully considering the different structural plane parameters after excavation. For further discussion, taking the deeply buried Guanshan railway tunnel under high in situ stresses as an example, according to the statistic analysis of the rock structural plane, this paper applied SMRM to analysis the outstanding anisotropy of rock mass after the excavation. Finally, suggestions of rock mass classification adjustment is offered to catch up with the degradation of rock mass after excavation.