Friction Bolt Assembly Radial Deformation Anchoring
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Solution Overview
Problem
Current friction bolts used in stabilizing mine roofs and walls often fail to provide sufficient anchoring due to insufficient frictional forces between the bolt and the rock strata, necessitating improvements in load transfer mechanisms.
Innovation Solution
A friction bolt assembly featuring a tubular body with a split and an expansion element mounted on a rod, which is actuated by a drive head to radially deform the bolt body, enhancing engagement with the rock strata and providing additional anchoring through a tapered engagement surface and load transfer fittings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If friction bolts are driven into bore holes relying on elastic deformation, then installation is simple, but anchoring force is insufficient
Solution Approach 1:
The friction bolt transitions from a static elastic deformation mechanism to a dynamic expansion mechanism. The expansion element is initially retracted within the tubular body during simple installation, then extended outward to engage with the bore hole wall, providing progressive anchoring force enhancement without complicating the installation process
Solution Approach 2:
The friction bolt is divided into functional segments: the tubular body providing structural support, the expansion element providing anchoring force, and the rod connecting them. This segmentation allows the expansion element to be actuated independently to provide additional anchoring force while maintaining the simplicity of the overall installation process
2Strength
If grout is used to increase rigidity, then load transfer improves, but installation complexity increases
Solution Approach 1:
The expansion element provides self-service load transfer enhancement by being actuated through rod extension. As the rod extends, it pushes the expansion element outward to engage with the bore hole wall, creating anchoring force without requiring external grout materials or additional installation steps
Solution Approach 2:
The expansion element acts as an intermediary between the friction bolt body and the bore hole wall. It transfers and amplifies the anchoring force through its engagement surface, providing enhanced load transfer capability without requiring the complex grout filling process
3Force
If radial deformation is applied after installation, then anchoring force increases, but additional operation steps are required
Solution Approach 1:
The expansion element's radial deformation action is merged with the rod extension operation. As the rod extends longitudinally, it simultaneously pushes the expansion element outward to deform radially and engage with the bore hole wall, combining two functions into one continuous motion
Solution Approach 2:
The expansion element transitions from a retracted state during installation to an extended engaged state during operation. This dynamic transformation allows the anchoring force to be enhanced through the same operational sequence used for installation, maintaining ease of operation while increasing anchoring capability
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 significantly increases the anchoring force of the friction bolt within the rock strata, ensuring stable retention and load transfer, even under dynamic conditions such as rock bursts or seismic events.
Implementation Method 1
radially outwardly deforming said friction bolt body at said friction bolt body leading end
Implementation Method 2
The frictional forces generated between the friction bolt and bore hole wall are at times insufficient to properly anchor the friction bolt within the bore hole
Implementation Method 3
the friction bolt body elastically deforms to reduce the size of the split in the body. This elastic deformation exerts radial forces against the wall of the hole, providing a corresponding frictional force, retaining the friction bolt within the hole
Data Source
AI summary
A friction bolt assembly has a tubular friction bolt body defining a cavity and having a split. A rod extends through the cavity. An expansion element is mounted on the rod at or toward the rod leading end and protrudes through the friction bolt body leading end. The expansion element has an engagement surface tapering toward the rod trailing end. A drive head is mounted on the rod at or adjacent the rod trailing end. The rod is actuatable by rotation of the drive head to draw the expansion element toward the friction bolt body trailing end such that the engagement surface engages the friction bolt body, radially outwardly deforming the friction bolt body.