Inflatable Rock Bolt Folded End Wall Stress Distribution
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Solution Overview
Problem
Inflatable rock bolts face durability issues in the stress placed on folded regions during expansion, leading to potential material weakening and leakage.
Innovation Solution
A sealed tubular rock bolt design featuring a cap welded onto one end, with a fold extending along the pipe, where the bottom of the fold integrates into the cap's sidewall, forming a U-shaped ridge, distributing stress more evenly and reducing lateral compression on the cap's end wall, enhancing durability and preventing leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rock bolt is expanded by introducing pressurised fluid into the folded tube body, then the rock bolt engages with the drill hole wall through friction, but the folded regions experience high stress leading to material weakening and potential leakage
Solution Approach 1:
The end wall is pre-formed with a curved configuration before the folding operation. This preliminary shaping ensures that during expansion, the stress is distributed more favorably across the folded regions, preventing material weakening and leakage while maintaining the sealing function.
Solution Approach 2:
The end wall is given a specific curved configuration in its forward region, creating local structural quality that differs from the rest of the tube. This localized curvature modification enhances the durability of the folded regions specifically, without affecting other parts of the rock bolt.
2Length of moving object
If the fold extends along the pipe to reduce cross-sectional profile for insertion, then the rock bolt can be inserted into the drill hole, but the folded regions experience lateral compression stress during expansion
Solution Approach 1:
The end wall curvature is established before the folding and expansion operations. This preliminary configuration prepares the structure to better withstand the lateral compression stresses that will occur during expansion, reducing the risk of material failure.
Solution Approach 2:
The geometric parameters of the end wall are modified by introducing a curved configuration. This parameter change alters the stress distribution characteristics during expansion, reducing lateral compression on the folded regions while maintaining the ability to engage with the drill hole wall.
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 design improves the durability of the rock bolt's folded regions during expansion, mitigating material weakening and preventing leaks, while maintaining a circular cross-sectional profile for effective engagement with drill holes.
Implementation Method 1
a cap (2) welded in sealing engagement onto an end of the pipe (3)
Implementation Method 2
the pipe (3) and the cap (2) are formed into an intermediate condition, which is accompanied by some lateral bulging or outward distortion to either side of the fold
Implementation Method 3
by introducing a pressurised fluid into an interior of the body
Implementation Method 4
the surface of the tube engages in the hole
Data Source
Figure 1
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Figure 3
AI summary
The invention relates to an inflatable rock bolt (1) and a method of manufacture. A cap (2) is welded onto an end of the pipe (3). A fold (9) is formed from a first side of the rock bolt (1), extending along a length of the pipe (3). A bottom (10) of the fold (9) is formed to extend from the pipe (3) into a sidewall (5) of the cap (2) and outwardly towards the first side to a position separated by a ridge (12) from a first portion (13) of the end wall that remains outside the fold (9), with a second portion (14) of the end wall drawn into the fold (9).