Prestressed Anchor Bolt with Decoupling for Deep Rock Deformation
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Solution Overview
Problem
Deep thin-bedded rock masses in high geostress environments experience rapid deformation leading to support structure damage, anchor bolt failure, and stress adjustment issues during tunnel excavation, necessitating a more effective control method and device for large deformation management.
Innovation Solution
An active control device comprising a high-strength prestressed anchor bolt with a reverse anti-skid device, resin anchoring agent, decoupling structure, and grouting system, which applies preload and allows for lag grouting to reinforce the surrounding rock, reducing the risk of anchor bolt failure and enhancing rock integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If common grouted anchor bolt support is used in deep thin-bedded surrounding rock, then the support structure can be simplified, but the anchor bolt will be pulled off or sheared due to large deformation and the surrounding rock breaks within a wide range
Solution Approach 1:
The anchor bolt system is segmented into multiple functional sections: a rigid head section for initial support, a flexible decoupling structure (geotextile wrapping) in the middle section to accommodate deformation, and a resin-anchored tail section for deep rock fixation. This segmentation allows each part to perform its specific function optimally while collectively preventing bolt pull-off and shear failure.
Solution Approach 2:
The middle section of the anchor bolt is wrapped with geotextile to create a decoupling structure that can dynamically adapt to surrounding rock deformation. This flexible wrapping allows the anchor bolt to move and deform with the rock mass rather than rigidly resisting it, preventing the bolt from being pulled off during large deformations while maintaining continuous support.
2Ease of manufacture
If traditional anchor bolt installation is used, then the installation process is simple, but the surrounding rock continues to crack due to long adjustment time of surrounding rock stress
Solution Approach 1:
The anchor bolt is pre-loaded with initial tension force during installation, and the resin anchoring agent is pre-applied to the tail end before insertion. This preliminary action ensures that the anchor bolt immediately provides active support to the surrounding rock upon installation, preventing crack development during the stress adjustment period without requiring complex post-installation operations.
Solution Approach 2:
The resin anchoring agent acts as an intermediary between the anchor bolt tail end and the surrounding rock. It fills the gap between the bolt and rock, providing continuous bonding and stress transfer while allowing for stress adjustment. This intermediary material prevents the rock from cracking during adjustment by maintaining constant contact and support.
3Loss of time
If high prestress is applied to the anchor bolt, then the timeliness of support is improved, but the anchor bolt may be sheared due to shear slip of surrounding rock along the layer
Solution Approach 1:
The anchor bolt system applies different mechanical properties to different sections: the head section provides high prestress for immediate support, the middle geotextile-wrapped section provides flexibility to accommodate shear deformation, and the resin-anchored tail section provides deep fixation. This local differentiation allows high prestress to be applied without causing shear failure, as each section is optimized for its specific function.
Solution Approach 2:
The anchor bolt combines multiple materials with different properties: steel for the bolt body (high strength), geotextile for the decoupling wrapping (flexibility), and resin anchoring agent for deep rock fixation. This composite construction allows the system to withstand both high prestress and shear forces by distributing loads across materials with complementary characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides timely and effective anchoring, reduces anchor bolt failure, maintains rock integrity, and adapts to deformation, enabling immediate support and subsequent reinforcement of the surrounding rock, thereby enhancing safety and reducing economic losses.
Implementation Method 1
a resin anchoring agent filling section located at the front end of the reverse anti-skid device and between the high-strength prestressed anchor bolt and the sleeve and formed by the applied resin anchoring agent by extending into the tail end of the deep thin-bedded surrounding rock
Implementation Method 2
a grouting device arranged side by side with the anchor bolt and capable of grouting; the grouting device can be extended into the sleeve after passing through the tray
Data Source
AI summary
An active control method and device for large deformation of a deep thin-bedded surrounding rock, the active control method includes: drill holes in the surrounding rock of a tunnel against a tunnel face, add the active control device containing a sleeve, a high-strength prestressed anchor bolt, a resin anchoring agent and a grouting device into drill holes, apply a preload to the anchor bolt when the resin anchoring agent has a certain strength, and carry out lag grouting in the surrounding rock through the grouting device after stress adjustment, and the high-strength prestressed anchor bolt and the grouting device are inserted in the sleeve with holes on the side. The active control device or method of the invention can effectively reduce the fracture depth and degree of a thin-bedded soft rock in deep engineering, and effectively inhibit the occurrence of large deformation disasters.