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采用高强石膏配制板裂化模型试样,选用铝棒制作预应力锚杆模型,通过一侧约束条件下的单轴压缩试验,研究板裂化模型试样的预应力锚杆锚固效应。试验结果表明:加锚试样的峰值强度、残余强度及弹性模量均有不同程度的提高,试样峰后侧向变形显著减小,且随着预应力值的增大效果更为显著;与无锚试件岩板压折、岩片弹射的失稳破坏现象相比,加锚试件保持了较好的完整性,局部发生岩板断裂、脱落现象;试样变形破坏过程中,锚杆轴向应力变化分为线性缓慢上升期、非线性增长期和急剧上升期3个阶段,锚杆轴向应力的变化规律反映了其自身工作机制及板裂化模型试样变形特征。分析锚固机制认为,预应力锚杆的施加不仅有效降低了预制裂隙尖端拉应力集中程度,体现出抑制裂隙扩展的止裂作用,而且将试样劈裂形成的岩板加固为整体,有效抑制了岩板向临空面的屈曲变形,进而提高了试样的临界失稳荷载值。最后,基于试验结果的认识,提出针对板裂化围岩的“及时支护、区域控制及重点加固”的锚喷支护控制策略。
The specimens of high-strength gypsum slab cracking model were prepared. The prestressed anchor model was made by using aluminum rods. The uniaxial compression test under the one-sided constraint was used to study the anchoring effect of prestressed anchors. The experimental results show that the peak strength, residual strength and elastic modulus of the anchored specimens increase to different extents, the lateral deformation of the specimens decreases significantly, and the effect becomes more obvious as the prestress value increases. Compared with the failure phenomenon of rockfill buckling and rock ejection, the anchored specimens maintained good integrity and the rock fragments were locally broken and dropped off. During deformation and failure of the specimens, the anchors The axial stress changes are divided into three stages: linear slow rising, non-linear increasing and rapid rising. The variation law of axial stress of rock bolt reflects its own working mechanism and deformation characteristics of plate cracking model. Analysis of the anchoring mechanism suggests that the application of prestressed anchor not only effectively reduces the concentration of tensile stress at the tip of prefabricated cracks, but also plays an important role in preventing the crack propagation. In addition, the rockfill formed by the splitting of the sample is strengthened as a whole and effectively restrained The buckling deformation of the rock slab towards the freeboard surface increases the critical buckling load value of the specimen. Finally, based on the experimental results, the control strategy of shotcrete and shotcrete support for “timely support, area control and key reinforcement” of rock mass is proposed.