Anchor Tendon with Selectively Deformable Portions for Rock Burst Absorption
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Solution Overview
Problem
Conventional mine roof and wall support systems face premature failure due to the inability of anchor tendons to plastically deform and absorb dynamic load forces, particularly in situations where ground movement exceeds the tendon's threshold fracture force, leading to increased risk of tendon breakage and loss of connection with rock surfaces.
Innovation Solution
The anchor bolt or tendon is designed with selectively formed deformable portions that can axially elongate and absorb load forces, featuring a rigid anchoring portion with primary anchoring members for secure engagement with grout and deformable sections that allow controlled plastic deformation to accommodate excessive rock forces, thereby distributing and dissipating energy without catastrophic failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the anchor tendon is made rigid to maintain structural stability, then the strength and load-bearing capacity are improved, but the tendon becomes susceptible to premature failure when ground movement exceeds the threshold fracture force
Solution Approach 1:
The anchor tendon is divided into multiple segments with different mechanical properties: a rigid anchoring portion with ribs for strong rock engagement, and a deformable portion with reduced ribs that can plastically deform. This segmentation allows the system to simultaneously achieve high strength through the rigid portion and reliability through the deformable portion that absorbs excess ground movement forces.
Solution Approach 2:
Different portions of the anchor tendon are given different local qualities: the anchoring portion has high rigidity with pronounced ribs for strong engagement, while the deformable portion has reduced rib height and spacing to allow plastic deformation. This local differentiation enables the tendon to exhibit both strength and ductility in appropriate locations.
2Strength
If the anchor tendon is made fully grouted and encapsulated to enhance bonding with rock strata, then the anchoring strength is improved, but the tendon loses the ability to plastically deform and absorb dynamic forces
Solution Approach 1:
The tendon is segmented into a fully grouted anchoring portion that provides strong bonding with rock strata, and a deformable portion that remains partially ungrouted or has reduced grout engagement to maintain plastic deformation capability. This allows the system to achieve both anchoring strength and adaptability to dynamic forces.
Solution Approach 2:
The grout encapsulation is applied locally and selectively: full encapsulation in the anchoring portion for maximum bonding strength, and reduced or no encapsulation in the deformable portion to preserve ductility and plastic deformation ability.
3Ease of manufacture
If the threaded section diameter is reduced to accommodate threading processes, then the ease of manufacture and installation are improved, but the tendon becomes a weak point prone to fracture under load
Solution Approach 1:
The threading operation is extracted and isolated to only the proximal end portion of the tendon that projects from the rock face. The main body of the tendon, including the deformable and anchoring portions, maintains full diameter without threading, eliminating weak points and preserving strength where it is most needed for load-bearing and rock engagement.
4Stability of the object's composition
If the anchor tendon is made completely rigid to prevent deformation, then the structural stability is improved, but the tendon cannot accommodate differential ground movement between dilating and fixed rock strata
Solution Approach 1:
The tendon is segmented into rigid anchoring portions that maintain structural stability and deformable portions that accommodate ground movement. The rigid portions with pronounced ribs provide stable anchoring in fixed rock strata, while the deformable portions with reduced ribs allow plastic deformation to accommodate differential movement between dilating and fixed rock zones.
Solution Approach 2:
The tendon transitions from a static, completely rigid structure to a dynamic system with portions that can change shape and length. The deformable portion is designed to plastically deform under excessive ground movement forces, allowing the tendon to adapt dynamically to changing ground conditions while maintaining overall structural integrity.
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
This design enhances the anchor bolt's ability to absorb and dissipate energy from rock bursts and dilation forces, reducing the likelihood of premature failure and maintaining rock stability by allowing controlled deformation and maintaining partial coupling with rock strata, thus minimizing rock fall and extending the bolt's operational lifespan.
Implementation Method 1
The deformable portions are configured to preferentially plastically deform and/or axially elongate in response to ground or load forces which exceed a predetermined threshold force, to assist in the absorption and dissipation of load forces.
Data Source
AI summary
A mine roof support system includes an elongated anchor rod or tendon having a rigid non-deformable distalmost anchoring end portion, and one or more axially deformable portions which are configured to deform in the event load forces exceed a threshold force approximating the forces during a rock burst or rock dilation event. The rigid anchoring portion is provided with primary anchor members such as ribs, grooves, studs and the like. The primary anchor members are configured to reduce bar plasticity, and fixedly secure and retain the rigid portion in place in a drill hole. In the event rock forces exceed the threshold force, the plastically deformable portions elongate with the dilating rock to accommodate and absorb the rock forces.