Rock Bolt Assembly with Compressed Tubular Sleeve
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Solution Overview
Problem
Existing rock bolt assemblies with grout sleeves suffer from reduced load transfer and stiffness due to the sleeve's inability to maintain a seal and allow full column grouting, leading to the need for additional mechanical anchors and increased complexity and cost.
Innovation Solution
A rock bolt assembly with a tubular sleeve that is compressed along band sections to reduce diameter over stem portions, preventing axial movement and maintaining a seal, while retaining the original diameter over anchor portions, allowing for improved anchoring properties without the need for mechanical anchors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a tubular sleeve is used to channel grout deep into the rock hole, then full column grouting is achieved, but load transfer from the rock bolt to the surrounding rock is reduced
Solution Approach 1:
The sleeve is designed with different properties in different locations: smooth sections for grout flow and profiled sections for load transfer. This local differentiation allows the sleeve to simultaneously enable full column grouting and maintain anchorage capacity without requiring mechanical anchors.
2Strength
If the sleeve is profiled with ridges or spiral to improve anchorage, then load transfer is enhanced, but the assembly cannot function at full load capacity and mechanical anchors are still required
Solution Approach 1:
The sleeve features localized profiling at specific positions (proximal and distal ends) rather than continuous profiling. This targeted approach provides sufficient anchorage at the ends while maintaining a smooth central section for effective grout flow and load distribution, achieving full load capacity without mechanical anchors.
Solution Approach 2:
The sleeve is divided into distinct functional segments: profiled end sections for anchorage and a smooth central section for grout flow. This segmentation allows each portion to optimize its specific function while working together as an integrated system.
3Adaptability or versatility
If the sleeve is allowed to move axially relatively to the bolt, then flexibility is increased, but the seal between the sleeve and the bush is broken and grout escapes
Solution Approach 1:
The sleeve design incorporates localized rigid profiling at the ends that acts as a mechanical stop, preventing axial movement that would compromise the seal. This localized constraint maintains sealing reliability while allowing the overall assembly to accommodate installation requirements.
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 enhances anchoring properties by maintaining a seal and allowing full column grouting, maximizing load transfer from the rock bolt to the surrounding rock, thereby eliminating the need for mechanical anchors and reducing costs.
Implementation Method 1
the tubular sleeve is adapted along at least one band section by a reduction in the first diameter in at least one diametric plane
Implementation Method 2
grout may be pumped into the inlet to pass through the grout conduit and emerge at the sleeve's distal end, after which the grout can flow between the assembly and the grout hole
Implementation Method 3
The invention relates to a rock bolt assembly which is adhered in a rock hole by a resinous or cementitious adhesive and which has improved grout or resin anchoring and/or stiffness properties
Data Source
AI summary
Disclosed is a rock bolt assembly including: a rock bolt with an elongate body which extends between a distal end and a proximal end and which has an integrally formed anchor portion and, where the body is not so formed, cylindrical stem portions; a tubular sleeve with a first diameter, which longitudinally extends between a first end and a second end, partially encasing the rock bolt so at least a proximal end portion of the bolt projects from the first end of the sleeve; a grout-input element which engages the rock bolt on the proximal end portion and which engages the first end of the sleeve in sealing contact; wherein, over each stem portion, the tubular sleeve is adapted along a band section by a reduction in the first diameter in a diametric plane; and wherein, over the anchor portion, the tubular sleeve retains the first diameter.