Understanding the axial load transfer mechanism of rock bolts under diverse conditions is essential for optimizing reinforcement in rock structures, advancing our comprehension of rock support, and facilitating the design of robust engineering solutions. This paper reports the outcomes of an extensive experimental investigation, focusing on the axial behavior of protective sheathed rock bolts employed in corrosive environments, assessed through pullout tests. Three distinct testing setups were designed to evaluate comprehensively the performance of these rock bolts in various scenarios. The results indicated that the failure characteristics and axial behaviors of sheathed rock bolts differ significantly from conventional counterparts. The findings revealed two primary failure modes in sheathed rock bolts: bolt rupture and slip at the grout-sheath interface, based on the testing arrangement and encapsulation length. The lack of adhesion and interlocking at the grout-sheath interface prevents shear stress at the bolt-grout interface from reaching its maximum potential strength, resulting in grout damage manifesting as circumferential cracks. This, in turn, initiates crack formation, reducing the system’s bond strength. Additionally, it causes slip at the grout-sheath interface to occur at lower pullout loads. It can be inferred that the inner surface of the plastic sheath lacks the necessary structural integrity to withstand high loads, significantly impacting bond stress distribution and failure modes. The results demonstrate that the protective sheath remains intact up to an axial displacement of 28 mm, irrespective of the testing configuration. Additionally, it was observed that the maximum bond stress at the bolt-grout interface falls within the range of 6–8.7 MPa, which is below the shear strength of the grout. Consequently, achieving failure at the bolt-grout interface is not feasible.

中文翻译：

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通过大规模测试探索保护铠装岩石锚杆的轴向性能


了解不同条件下岩石锚杆的轴向载荷传递机制对于优化岩石结构的加固、促进我们对岩石支护的理解以及促进设计稳健的工程解决方案至关重要。本文报告了一项广泛的实验调查的结果，重点是在腐蚀环境中采用的保护性铠装岩石锚杆的轴向行为，并通过拉拔测试进行评估。设计了三种不同的测试设置，以全面评估这些岩石锚杆在各种情况下的性能。结果表明：铠装锚杆的破坏特性和轴向行为与常规锚杆存在显著差异。研究结果揭示了护套岩石锚杆的两种主要破坏模式：基于测试布置和封装长度，锚杆破裂和灌浆-护套界面处的滑移。灌浆-护套界面处缺乏粘附力和互锁，阻止了螺栓-灌浆界面处的剪切应力达到其最大潜在强度，导致灌浆损伤表现为周向裂纹。这反过来又会引发裂纹形成，从而降低系统的粘合强度。此外，它还会导致在较低的拉出载荷下在灌浆-护套界面处发生滑动。可以推断，塑料护套的内表面缺乏承受高负载所需的结构完整性，从而显着影响粘结应力分布和失效模式。结果表明，无论测试配置如何，保护套在 28 mm 的轴向位移下都保持完整。此外，还观察到螺栓-灌浆界面处的最大粘结应力在 6-8 的范围内。7 MPa，低于灌浆的剪切强度。因此，在螺栓-灌浆界面处发生失效是不可行的。