Exploring the axial performance of protective sheathed rock bolts through large-scale testing

IF 6.7 1区 工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY
Hadi Nourizadeh , Ali Mirzaghorbanali , Kevin McDougall , Naj Aziz
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Abstract

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.
通过大规模试验探索保护性铠装岩石螺栓的轴向性能
了解岩石螺栓在不同条件下的轴向载荷传递机制,对于优化岩石结构加固、提高我们对岩石支撑的理解以及促进稳固工程解决方案的设计至关重要。本文报告了广泛的实验研究成果,重点关注在腐蚀环境中使用的保护性铠装岩石螺栓的轴向行为,并通过拉拔测试进行评估。设计了三种不同的测试装置,以全面评估这些岩石螺栓在各种情况下的性能。结果表明,护套岩石螺栓的失效特征和轴向行为与传统的同类产品有很大不同。研究结果表明,根据测试布置和封装长度,岩石锚杆护套主要有两种失效模式:锚杆断裂和灌浆-护套界面滑移。由于灌浆料-护套界面缺乏粘附性和互锁性,螺栓-灌浆料界面的剪切应力无法达到最大潜在强度,导致灌浆料损坏,表现为周向裂缝。这反过来又会导致裂缝形成,降低系统的粘结强度。此外,它还会导致灌浆料-护套界面在较低的拉拔荷载下发生滑移。由此可以推断,塑料护套的内表面缺乏必要的结构完整性以承受高荷载,从而对粘结应力分布和失效模式产生重大影响。结果表明,无论测试结构如何,保护套在轴向位移达 28 毫米时仍保持完好。此外,还观察到螺栓-灌浆料界面的最大粘结应力在 6-8.7 兆帕范围内,低于灌浆料的剪切强度。因此,在螺栓-灌浆界面上实现破坏是不可行的。
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来源期刊
Tunnelling and Underground Space Technology
Tunnelling and Underground Space Technology 工程技术-工程:土木
CiteScore
11.90
自引率
18.80%
发文量
454
审稿时长
10.8 months
期刊介绍: Tunnelling and Underground Space Technology is an international journal which publishes authoritative articles encompassing the development of innovative uses of underground space and the results of high quality research into improved, more cost-effective techniques for the planning, geo-investigation, design, construction, operation and maintenance of underground and earth-sheltered structures. The journal provides an effective vehicle for the improved worldwide exchange of information on developments in underground technology - and the experience gained from its use - and is strongly committed to publishing papers on the interdisciplinary aspects of creating, planning, and regulating underground space.
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