Yieldable Mine Bolt With Non-Threaded Section
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Solution Overview
Problem
Mine roof bolts are vulnerable to failure under dynamic loading conditions such as rock bursts due to susceptibility of rock formations in hard rock mining, necessitating improved designs that can absorb and accommodate such forces without compromising structural integrity.
Innovation Solution
A mine bolt design featuring an elongated body with a first and second threaded section and a smooth, non-threaded section positioned between them, where the non-threaded section is more ductile and yieldable than the threaded sections, allowing it to de-bond from grout under loading, and is heat-treated to enhance its yieldability, along with a drill bit at one end for self-drilling capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the mine roof bolt is designed with uniform strength throughout, then the bolt maintains high tensile strength for anchoring, but it becomes vulnerable to failure under dynamic loading such as rock bursts
Solution Approach 1:
The bolt is divided into distinct segments with different properties: a yieldable intermediate section and stronger end sections. This segmentation allows the bolt to have high anchoring strength at the ends while incorporating a vulnerable section that can yield to absorb rock burst energy, resolving the contradiction between maintaining high strength and preventing failure under dynamic loading.
Solution Approach 2:
The bolt features localized variation in material properties and geometry, with the intermediate section having reduced cross-sectional area or modified material characteristics compared to the end sections. This local quality change creates a predetermined yield point that absorbs dynamic loads while preserving the high strength anchoring capability of the end sections.
2Reliability
If the entire bolt is made yieldable to absorb dynamic loading, then the bolt can accommodate rock bursts, but it loses anchoring capability and structural integrity
Solution Approach 1:
The bolt is segmented into a yieldable intermediate section and strong end sections. Only the intermediate section is designed to yield under dynamic loading, while the end sections maintain high strength for anchoring. This segmentation resolves the contradiction by localizing the yieldable property to where it is needed for energy absorption while preserving anchoring strength elsewhere.
Solution Approach 2:
The yieldable property is applied locally to the intermediate section through material selection, heat treatment, or geometric modification, while the end sections maintain their high strength properties. This localized application of different material qualities allows the bolt to simultaneously achieve both yieldability for dynamic load absorption and high strength for anchoring.
3Strength
If the bolt uses threaded sections throughout for anchoring, then it provides secure bonding with grout, but it lacks the ability to yield under loading
Solution Approach 1:
The threaded configuration is segmented and applied only to the end sections of the bolt where anchoring is required, while the intermediate section is left smooth or with reduced threading. This segmentation allows the threaded sections to provide secure grout bonding for anchoring while the smooth intermediate section can yield under dynamic loading without the constraint of threads.
Solution Approach 2:
The threaded surface quality is applied locally to the end sections to maximize bonding strength with grout, while the intermediate section has a different surface quality (smooth or minimally threaded) that facilitates yielding. This local differentiation of surface quality resolves the contradiction between needing threaded anchoring and requiring yieldability.
4Reliability
If the bolt is designed to be fully ductile for yieldability, then it can deform to absorb rock burst energy, but it loses the structural rigidity needed for effective anchoring
Solution Approach 1:
The bolt's structural properties are segmented along its length, with the intermediate section designed for high ductility and the end sections designed for high rigidity and strength. This segmentation allows the intermediate section to deform and absorb energy while the rigid end sections maintain structural integrity and provide effective anchoring.
Solution Approach 2:
Different material qualities are applied locally: the intermediate section has high ductility through material selection or heat treatment, while the end sections have high rigidity and strength. This local differentiation of material qualities resolves the contradiction between needing ductility for energy absorption and rigidity for anchoring.
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 effectively absorbs dynamic loading forces, reducing the risk of bolt failure by allowing the non-threaded section to yield, while the threaded sections engage and bond with grout for secure anchoring, thereby enhancing the bolt's ability to withstand rock bursts and maintain structural integrity.
Implementation Method 1
the non-threaded section is more ductile and yieldable than the threaded sections of the elongated body
Implementation Method 2
The non-threaded section is configured to yield under loading when the mine bolt is installed with grout in a bore hole
Implementation Method 3
is heat-treated to enhance its yieldability
Implementation Method 4
the threaded sections engage and bond with grout for secure anchoring
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
A mine bolt includes an elongated body having a first end and a second end positioned opposite the first end, with the elongated body having a first threaded section, a second threaded section, and a non-threaded section positioned between the first threaded section and the second threaded section. The non-threaded section is configured to yield under loading when the mine bolt is installed with grout in a bore hole.