缓倾层状隧道围岩各向异性渐进破裂特征

Anisotropic progressive fracture characteristics of surrounding rock in gently inclined layered tunnels

关键词:  缓倾层状围岩  渐进破裂  破坏特征  颗粒流  各向异性

Key words:  gently inclined layered surrounding rock  progressive rupture  failure characteristics  particle flow  anisotropy

摘要:

为研究隧道缓倾层状围岩受结构面影响的宏观各向异性渐进破裂特征及破坏模式,解析推导了层状围岩结构失稳力学响应机制；采用离散元有限差分耦合分析方法,结合室内砂泥岩三轴压缩力学试验,建立了能表征缓倾层状围岩宏观力学特性的数值力学模型,系统研究了不同结构面倾角和间距条件下缓倾层状岩体的破裂特征与破裂演化力学行为。结果表明:1）基于梁板结构的解析分析能较好反映层状围岩渐进破裂过程并判别其破坏模式；2）建立的离散元有限差分耦合数值模型能较好表征层状砂泥岩在三轴应力状态下各向异性宏观力学特性；3）基质体破裂随结构面倾角改变发生显著变化,裂隙主要出现在垂直结构面方向,且随结构面倾角增加,基质体破裂发生二次偏转,并计算得出围岩发生滑移破坏的临界角度α₁=24.43°,α₂=55.29°；4）随结构面间距减小,围岩破碎性增加,总裂隙数量增加,在结构面间距小于30 cm时,围岩破碎性显著提高。研究成果可为缓倾层状隧道围岩稳定性控制与支护结构优化设计提供理论依据并发挥指导作用。

Abstract:

To study the Macro-anisotropic progressive rupture characteristics and damage modes of gently inclined layered surrounding rock influenced by structural planes, we analytically deduced the mechanical response mechanism of the layered rock′s structural instability. Using a coupled discrete-finite-difference analysis method and results from indoor triaxial compression tests on sand-mudstone, we developed a numerical mechanical model to characterize the macro-mechanical properties of the gently inclined layered surrounding rock. This model was then used to systematically investigate the mechanical behavior of the rock under varying structural plane inclination angles and spacings. The rupture characteristics and rupture evolution of gently dipping layered rock under different structural plane inclination angle and spacing are systematically studied. The results indicate that: 1)analytical analysis based on beam plate structure can better reflect the progressive fracture process of layered surrounding rock and distinguish its failure mode; 2)The established discrete element finite difference coupled numerical model can better characterize the anisotropic macroscopic mechanical properties of layered sand and mudstone under triaxial stress state; 3)The fracture of the matrix changes significantly with the change of the inclination angle of the structural plane, and the cracks mainly appear in the direction perpendicular to the structural plane, as the inclination angle of the structural plane increases, the matrix fracture will undergo secondary deflection, and the critical angle for sliding failure of the surrounding rock will be calculated α₁=24.43°, α₂=55.29°; 4)As the spacing between structural planes decreases, the fragmentation of surrounding rock increases and the total number of cracks increases. When the spacing between structural planes is less than 30 cm, the fragmentation of surrounding rock significantly increases. The research results can provide a certain theoretical basis and play a guiding role for the control of stability and optimal design of supporting structures for gently inclined layered tunnels.