中文摘要：

基于Hoek-Brown强度准则及量化GSI围岩评级系统，分析岩体强度弱化行为，总结出确定岩体峰值及峰后强度参数的方法，提出应变软化模型的简化计算方法，并以FLAC3D数值模拟软件为工具，采用收敛-约束法对深埋大断面隧道支护结构及围岩稳定性进行分析，计算出支护结构安全系数。通过分析得出：随着围岩应力释放，岩体软化参数随之减小，岩体强度弱化行为突出；高地质强度GSI指标（GSI=75）的岩体虽然强度弱化程度较大，但围岩的变形量仍然较小，而低GSI指标（GSI=25）的岩体表现出了理想弹塑性行为；提出的简化Hoek-Brown应变软化模型适合应用于隧道中岩质相近区段围岩的研究；采用收敛-约束法对隧道支护结构的稳定性进行分析，可为隧道工程的初期支护优化设计及安全性评价提供参考。

英文摘要：

Based on the Hoek-Brown strength criterion and geological strength index （GSI） surrounding rock rating system, rock strength weakening behavior is analyzed, a method to determine the rock peak and the peak strength parameters is summarized, a simplified calculation method for the strain-softening model is proposed. By using FLAC3D numerical simulation software, and based on convergence constraint method, the stability of surrounding rock and the support in buried large section tunnel are analyzed, and the safety factor for supporting structure is calculated. The results show that： with the release of the rock stress, rock softening parameter decreases and strength weakening behavior becomes severe. Although the high GSI （GSI = 75） for rock, strength weakening is serious, the deformation is still small. For low GSI （GSI = 25） of the rock showing the perfect elastoplastic behavior. The proposed simplified Hoek-Brown strain-softening model is suitable for the tunnel close to the rock section of the surrounding rock. The convergence constraint method is applied to analyzing the stability of surrounding rock and support, which could provide a reference for initial support to optimize the design and safety evaluation in tunnels.