基于GDEM的结构面型岩爆孕育演化机制

Evolution and mechanism of rockburst induced by structural plane based on GDEM

  • 摘要: 深部硬岩工程开挖过程中,洞壁围岩常常因结构面的存在发生岩爆地质灾害,造成人员伤亡和设备损毁等事故。通过采用有限元、离散元相耦合的GDEM数值仿真技术研究了边墙含竖向结构面的数目和尺度对深部硬岩直墙拱形隧道在开挖卸荷作用下,围岩裂化扩展行为、应力、位移、片状块体速度等力学运动特征的影响,以此揭示围岩板裂化、结构面型岩爆之间的演化机制。结果表明:开挖卸荷后,含多结构面数目隧道的破坏模式及强度与结构面控制效应有关(洞壁径向距离1.5 m范围内结构面的作用影响大),且结构面具有主导控制岩爆爆坑边界的作用,而多节理岩板裂化的演化机制为切应力不均匀分布,致使岩板实际承载偏心受压,产生二阶弯矩效应,诱发强烈的张拉板裂型岩爆,呈现出“平底锅状”C字型的爆坑;围岩破坏强度与岩板的尺度效应有关且结构面具有削弱应力向径向深部围岩转移的阻碍作用,从而不断加剧结构面围岩之间卸荷应力波的相互反射,增大了岩板内的应力积聚与能量积累。且尺度不同,其切应力调整分布演化差异大,大尺度高柔度的三节理岩板,其端部载荷强度高、岩板的屈曲效应较明显,导致径向内部岩板易屈曲失稳而引发边墙围岩板端部的剪断失稳破坏,诱发强烈岩爆。而中小尺度的三节理岩板,柔度小不易失稳,且载荷作用小,裂纹易沿结构面尖端扩展贯通破坏,呈现为脱落型静态脆性破坏,形成小V型破坏断口。

     

    Abstract: In the process of deep underground rock excavation, the surrounding rock of cave wall often causes some rockburst geological disasters due to the weakening of structural plane. In order to reveal the influence of the existence of structural plane on the rockburst induction mechanism, in this paper, adopting the finite element and discrete element coupled GDEM numerical simulation technology, the influences of the number and scale of vertical structural planes on the mechanical characteristics of rock cracking propagation, stress, displacement and slab velocity of deep hard rock straight arch tunnel under excavation and unloading are studied, and the evolutionary mechanism between wall cracking and structural plane rockburst is revealed. Results indicate that the failure modes and intensity for the surrounding rock with multiple structural planes are associated with the controlling effect of the structural plane, especially within 1.5 m away from the tunnel side, and the weak plane can act as the boundary of the rockburst cater. The uneven distribution of the tangential stress and the eccentric compression of the rock plates separated by the weak plane will induce intense slabbing rockburst. The size of the structural plane will also affect the intensity of the surrounding rock failure, and the stress transfer to the deep rockmass will be impeded. Three-jointed rock slab with large scale and high flexibility has high end load strength and obvious buckling effect of rock slab, which leads to radial internal rock slab buckling and triggering shear instability failure at the end of side wall surrounding rock slab and strong rock burst. However, with the small and medium scale three-jointed slab, the flexibility of the rock plate is small and the rock plate is stable, leading to the quasi-static brittle failure of the surrounding rock, and forming a small V-type destructive fracture port.

     

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