Investigation of the failure mechanism and theoretical model of bolt-reinforced shallow tunnel faces with different bolt lengths

IF 8.2 1区 工程技术 Q1 ENGINEERING, CIVIL
Xiao Zhang , Li Yu , Mingnian Wang , Henghong Yang , Ming Lu , Zexing Li , Langzhou Tang
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引用次数: 0

Abstract

Using fiberglass bolts to reinforce a tunnel face is a practical auxiliary technology for ensuring tunnel face stability in soft ground. The reinforcing effect and the economics of this technology are significantly affected by bolt length. However, to date, the failure mechanism of bolt-reinforced tunnel faces with different bolt lengths has rarely been investigated. To reveal the failure mechanism of bolt-reinforced shallow tunnel faces, in this study, the stability of bolt-reinforced tunnel faces with different bolt lengths was investigated by using laboratory tests and numerical simulations, and a simplified theoretical model for practical engineering was proposed. The face support pressure and failure pattern for different bolt lengths during the face collapse process were obtained, and the influence of bolt length on face stability was clearly revealed. More specifically, the results show that face stability increases with increasing bolt length, and the reinforcing effect of face bolts is governed by the shear failure at the soil-grout interface first in the stable zone of the tunnel face and then in the failure zone. Once the bolt length in the stable zone is larger than that in the failure zone, face stability will not be improved with increasing bolt length; thus, this bolt length is referred to as the optimal bolt length Lopt. The Lopt value is slightly larger than the initial failure range (in the unreinforced condition) and can be approximately calculated by Lopt = (1 − 0.0133φ)D (φ is the friction angle of the soil, and D is the tunnel diameter) in practical engineering. Finally, a simplified theoretical model was established to analyse the stability of reinforced tunnel faces, and the results are in good agreement with both laboratory tests and numerical simulations. The proposed model can be used as an efficient tool for the design of face bolts.

不同螺栓长度的螺栓加固浅层隧道工作面的破坏机理和理论模型研究
使用玻璃纤维螺栓加固隧道工作面是确保软土地基隧道工作面稳定性的一项实用辅助技术。该技术的加固效果和经济性受到螺栓长度的显著影响。然而,迄今为止,对不同螺栓长度的螺栓加固隧道工作面的破坏机理研究还很少。为了揭示螺栓加固浅埋隧道工作面的破坏机理,本研究通过实验室试验和数值模拟研究了不同螺栓长度的螺栓加固隧道工作面的稳定性,并提出了适用于实际工程的简化理论模型。研究获得了不同螺栓长度的工作面支撑压力和工作面坍塌过程中的破坏模式,清楚地揭示了螺栓长度对工作面稳定性的影响。具体而言,结果表明,工作面稳定性随螺栓长度的增加而增加,工作面螺栓的加固效果受隧道工作面稳定区土-灌浆界面剪切破坏的支配,先稳定区后破坏区。一旦稳定区的螺栓长度大于破坏区的螺栓长度,工作面的稳定性将不会随着螺栓长度的增加而提高,因此,该螺栓长度被称为最佳螺栓长度 Lopt。Lopt 值略大于初始破坏范围(未加固条件下),在实际工程中可近似计算 Lopt = (1 - 0.0133φ)D(φ 为土壤摩擦角,D 为隧道直径)。最后,建立了一个简化的理论模型来分析加固隧道面层的稳定性,其结果与实验室试验和数值模拟结果十分吻合。所提出的模型可作为设计工作面螺栓的有效工具。
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来源期刊
Underground Space
Underground Space ENGINEERING, CIVIL-
CiteScore
10.20
自引率
14.10%
发文量
71
审稿时长
63 days
期刊介绍: Underground Space is an open access international journal without article processing charges (APC) committed to serving as a scientific forum for researchers and practitioners in the field of underground engineering. The journal welcomes manuscripts that deal with original theories, methods, technologies, and important applications throughout the life-cycle of underground projects, including planning, design, operation and maintenance, disaster prevention, and demolition. The journal is particularly interested in manuscripts related to the latest development of smart underground engineering from the perspectives of resilience, resources saving, environmental friendliness, humanity, and artificial intelligence. The manuscripts are expected to have significant innovation and potential impact in the field of underground engineering, and should have clear association with or application in underground projects.
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