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Influence of the Elastic Modulus and Spiral Rib Appearance on the Resin Bonding Performance Based on an NPR Prestressed Bolt

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Rock Mechanics and Rock Engineering
Authors:
Jiawang Zhan
Jiawang Zhan
Jiawang Zhan
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Jun Yang
Jun Yang
Jun Yang
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Wenhui Bian
Wenhui Bian
Wenhui Bian
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Zhigang Tao
Zhigang Tao
Zhigang Tao
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Abstract and Figures

This paper proposes a high-strength prestressed bolt that experiences both high strength and high elongation. Its elastic modulus is larger, and spiral ribs appear, which is referred to as the NPR bolt. The influence of different elastic moduli and spiral appearances on the bonding performance of the resin was analyzed. Theoretical analysis and FEM are used to analyze the influence of different elastic moduli on the mechanical distribution of the resin–rock interface. The results of the two methods are consistent. The maximum values of the interface shear stress and the axial force appear at the loading end, the minimum values appear at the end of the bolt, and both decays exponentially. With the increase in the elastic modulus of the bolt, the attenuation rate decreases, and the distribution becomes more uniform. The greater the elastic modulus is, the more positive the bonding performance of the resin–rock interface. The load transfer mechanism of the bolt–resin interface of a spiral rib under axial force was studied. With the same diameter and rib height, the spiral ribs of the NPR bolt can be more fully combined with the bonding agent to bear a greater tension load. Taking the NPR spiral and T-1 bolt used in this paper as examples, the bonding performance of the former is 2.24 times that of the latter. The loads of the spiral bolt and the inclined rib bolt are mainly borne by the ribs, accounting for 98.4% and 96.9%, respectively. The resin bonding performance experiment was carried out on an NPR spiral and commonly used T-1\T-2 resin bolts. From the experimental results, the spiral rib structure of the NPR bolt has excellent bonding performance with the resin, which can fully guarantee the bonding performance between the bolt–resin interface. With a resin anchor length of 600 mm, the average peak axial force of the NPR spiral bolt reaches 207 kN, and those of the T1 and T2 bolts are 163 kN and 139 kN, respectively. The NPR spiral bolts did not fail at the bolt–resin interface. Failure of the 1/4T-1 bolt and 3/4T-2 bolt occurred at the bolt–resin interface. The research results of this paper can provide a reference basis for the anchorage design of similar high-strength bolts with a spiral appearance.
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Vol.:(0123456789)
Rock Mechanics and Rock Engineering
https://doi.org/10.1007/s00603-024-04208-7
ORIGINAL PAPER
Influence oftheElastic Modulus andSpiral Rib Appearance
ontheResin Bonding Performance Based onanNPR Prestressed Bolt
Jiawang Zhan1,2 · Jun Yang1,2 · Wenhui Bian1,2 · Zhigang Tao1,2 · Manchao He1,2
Received: 1 March 2024 / Accepted: 7 October 2024
© The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature 2024
Abstract
This paper proposes a high-strength prestressed bolt that experiences both high strength and high elongation. Its elastic modu-
lus is larger, and spiral ribs appear, which is referred to as the NPR bolt. The influence of different elastic moduli and spiral
appearances on the bonding performance of the resin was analyzed. Theoretical analysis and FEM are used to analyze the
influence of different elastic moduli on the mechanical distribution of the resin–rock interface. The results of the two methods
are consistent. The maximum values of the interface shear stress and the axial force appear at the loading end, the minimum
values appear at the end of the bolt, and both decays exponentially. With the increase in the elastic modulus of the bolt, the
attenuation rate decreases, and the distribution becomes more uniform. The greater the elastic modulus is, the more positive the
bonding performance of the resin–rock interface. The load transfer mechanism of the bolt–resin interface of a spiral rib under
axial force was studied. With the same diameter and rib height, the spiral ribs of the NPR bolt can be more fully combined
with the bonding agent to bear a greater tension load. Taking the NPR spiral and T-1 bolt used in this paper as examples, the
bonding performance of the former is 2.24 times that of the latter. The loads of the spiral bolt and the inclined rib bolt are
mainly borne by the ribs, accounting for 98.4% and 96.9%, respectively. The resin bonding performance experiment was car-
ried out on an NPR spiral and commonly used T-1\T-2 resin bolts. From the experimental results, the spiral rib structure of
the NPR bolt has excellent bonding performance with the resin, which can fully guarantee the bonding performance between
the bolt–resin interface. With a resin anchor length of 600mm, the average peak axial force of the NPR spiral bolt reaches 207
kN, and those of the T1 and T2 bolts are 163 kN and 139 kN, respectively. The NPR spiral bolts did not fail at the bolt–resin
interface. Failure of the 1/4T-1 bolt and 3/4T-2 bolt occurred at the bolt–resin interface. The research results of this paper can
provide a reference basis for the anchorage design of similar high-strength bolts with a spiral appearance.
Highlights
• A new type of prestressed anchor bolt with high strength and high elongation is proposed, which is anchored by resin
and mechanical-type anchorage. Its elastic modulus is larger, and its appearance adopts the design of spiral ribs.
• The influence of the elastic modulus of the bolt on the bonding performance of the resin–rock interface was revealed. Under
the same axial load, the larger the elastic modulus of the bolt, the more uniform the interface shear stress distribution.
• The mechanical transfer model of the spiral rib bolt–resin interface was established and analyzed. In addition, the experi-
ment was carried out. Under the same bolt diameter and rib height, the interaction area between the spiral rib and the
resin is larger, which can provide greater load.
* Jun Yang
yjlr@163.com
1 State Key Laboratory forTunnel Engineering, China
University ofMining andTechnology (Beijing),
Beijing100083, China
2 School ofMechanics andCivil Engineering, China
University ofMining andTechnology (Beijing),
Beijing100083, China
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