为解决软岩大变形隧道中主动支护特征模糊与主动支护效用不明等问题，首先，采用理论分析与数值模拟相结合的方法，对及时支护、主动支护、强支护以及支护力扩散的支护作用进行分析； 其次，采用数值仿真研究及时-强-主动支护、及时-主动支护、强-主动支护、主动支护、强-被动支护、被动支护6种支护模式在不同围岩挤压度工况下的支护效用。得到主要结论如下： 1）软岩大变形隧道主动支护是在主动支护基础上叠加及时支护和强支护于一体，且具备充分扩散支护力属性的及时-强-主动支护； 2）主动支护力扩散的重要作用体现在支护力越扩散，围岩变形控制效果越好，并且能够有效减少支护薄弱区、提升围岩稳定性； 3）在主动支护基础上实施强支护或及时支护均能够有效提升支护效果，表现为围岩自身承载性能与围岩变形均能得到改善； 4）在主动支护基础上实施的及时-强-主动支护，其围岩变形控制效果与承载能力提升效果优于及时主动支护与强-主动支护的线性叠加，具有“1+1>2”的“放大”作用，且随围岩挤压度增加，该“放大”作用持续增大。
To address the ambiguous characteristics and undefined application effects of active support adopted in soft rock large-deformation tunnels, the support mechanisms of timely support, active support, high-strength support and support pressure diffusion are explored using theoretical analyses and numerical methods. Then, numerical simulations are carried out to analyze the supporting effects of six typical support schemes under different surrounding rock squeezing degrees, namely timely-high-strength-active support, timely-active support, high-strength-active support, single active support, high-strength-passive support, and passive support. The main conclusions are drawn as follows: (1) The core active support form suitable for soft rock large-deformation tunnels is timely-high-strength-active support, which integrates timely support and high-strength support based on conventional active support and features adequate support pressure diffusion performance. (2) Support pressure diffusion exerts a prominent influence on tunnel support: wider diffusion range of support pressure achieves better control effect on surrounding rock deformation, effectively eliminates weak support zones and improves surrounding rock stability. (3) The arrangement of high-strength support or timely support on the basis of active support markedly optimizes the overall support effect, and effectively improves both the self-bearing capacity and deformation state of surrounding rock. (4) The surrounding rock deformation control and bearing capacity improvement effects of timely-high-strength-active support are superior to the linear superposition effect of timely-active support and high-strength-active support, presenting an obvious “1+1>2” amplification effect. Moreover, such amplification effect increases continuously with the rise of surrounding rock squeezing degree.
