Rock Bolt Failure Arrestor Prevents Ejection
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Solution Overview
Problem
In ungrouted rock anchor applications, the steel material deforms to its maximum tensile capacity and is prone to snapping, causing the detached portion to eject from the rock hole with great force, posing a danger to mine workers.
Innovation Solution
A rock anchor assembly featuring a resiliently radially deformable tubular member with an arrestor formation and an elongate element that includes a break formation and a failure arrestor, which engages to arrest the ejectment of the proximal portion when the elongate element breaks, preventing ejection from the rock hole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the steel material of the rock anchor is allowed to deform to its maximum tensile capacity, then the energy absorption capability is improved, but the anchor becomes prone to snapping and creating a dangerous projectile
Solution Approach 1:
The failure arrestor is pre-positioned on the elongate element at a predetermined location, and the arrestor formation is pre-formed on the tubular member, so that when the elongate element breaks at the break formation, the failure arrestor automatically engages with the arrestor formation to arrest the detached portion before it can become a dangerous projectile
Solution Approach 2:
The invention converts the harmful effect of the anchor snapping into a beneficial controlled failure mode. The break formation is designed to break in a controlled manner, and the failure arrestor mechanism transforms the dangerous ejectment motion into a controlled engagement with the arrestor formation, thereby eliminating the projectile hazard while maintaining the energy absorption benefit
2Object-affected harmful factors
If the failure arrestor is positioned to engage immediately upon loading, then the ejection hazard is prevented, but the elongate element cannot fully utilize its tensile load capacity for energy absorption
Solution Approach 1:
The failure arrestor is pre-positioned at a specific location on the elongate element, and the break formation is designed at a predetermined distance from the failure arrestor. This preliminary arrangement ensures that the elongate element can elongate to its full tensile load capacity before the break formation fails, allowing maximum energy absorption. Only after this controlled break does the failure arrestor engage with the arrestor formation to prevent ejection
Solution Approach 2:
The design allows the elongate element to undergo partial elongation beyond its normal operating range, up to its maximum tensile capacity, before the failure arrestor mechanism activates. This partial excessive action enables full energy absorption while the failure arrestor remains dormant until the break formation fails, at which point it activates to arrest the detached portion
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 effectively arrests the detached portion of the steel anchor, preventing it from becoming a projectile and ensuring safety by allowing the elongate element to stretch to its tensile load capacity without premature engagement of the arrestor, thereby absorbing energy and preventing catastrophic failure.
Implementation Method 1
a resiliently radially deformable tubular member which longitudinally extends between a leading end and a trailing end
Implementation Method 2
the elongate element is adapted with a break formation between the failure arrestor and the first end
Data Source
Figure 1~1A
Figure 2~2A
Figure 3
AI summary
The invention provides a rock anchor assembly which includes: a resiliently radially deformable tubular member which longitudinally extends between a leading end and a trailing end and which has an arrestor formation integral with, or engaged to, a trailing end part of the member; an elongate element which longitudinally extends through the member between a first end and a second end and which attaches to the tubular member at spaced distal and proximal load points and which has a failure arrestor fixed at a point within the member; a faceplate on the tubular member or the elongate member; wherein, when the assembly is inserted in a rock hole, with the faceplate bearing against the rock face, and load is applied along the elongate element that will cause the element to sever above the point at which the arrestor is fixed, the failure arrestor engages the arrestor formation to arrest the ejectment of a proximal portion of the elongate element from the rock hole.