Rock Bolt with Segmented Anchors and Dynamic Stems
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Solution Overview
Problem
Existing rock bolts reliant on grout interaction for local anchoring are inadequate in providing comprehensive reinforcement against deformation and dilation in highly stressed rock masses.
Innovation Solution
A rock bolt design featuring a mechanical anchor for active engagement and resistive anchors for passive loading, with elongate stem portions allowing for dynamic movement, ensuring stable anchoring through multiple anchor points within the borehole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rock bolt uses only grout interaction for anchoring, then the anchoring mechanism is simple, but the reinforcement effectiveness against deformation and dilation is insufficient
Solution Approach 1:
The rock bolt is divided into multiple anchor zones with different anchor types (mechanical anchor at distal end, resin anchor in middle, grout anchor at proximal end). Each segment serves a specific anchoring function, creating a multi-stage anchoring system that improves overall reliability while distributing the complexity across functional segments rather than using a single complex anchor type throughout.
Solution Approach 2:
Different anchor types are applied at different locations along the rock bolt based on local requirements. The mechanical anchor provides strong anchoring at the distal end where rock stress is highest, the resin anchor provides intermediate anchoring in the middle section, and the grout anchor provides anchoring at the proximal end near the bearing plate. This local differentiation optimizes anchoring effectiveness without requiring uniform complexity throughout the entire bolt.
2Adaptability or versatility
If a rock bolt uses multiple anchor types with elongate stem portions, then the ability to accommodate dynamic loads improves, but the device complexity increases
Solution Approach 1:
The rock bolt incorporates elongate smooth cylindrical stem portions between the anchors that can elongate and move relative to the grouted borehole surround. This dynamic capability allows the stem portions to stretch and absorb energy during rock deformation and dilation events, accommodating dynamic loads while maintaining anchor integrity. The dynamic element is localized to specific stem portions rather than the entire bolt structure.
Solution Approach 2:
The rock bolt uses a composite anchoring system combining different anchor types (mechanical expansion anchor, resin-impregnated anchor, and grout anchor) along with smooth cylindrical stem portions. This composite approach integrates multiple anchoring mechanisms and material properties (rigid anchors for stable anchoring, flexible stem portions for dynamic movement) to achieve adaptability to various loading conditions while distributing structural complexity across different components.
3Ease of operation
If the stem portions are smooth and cylindrical, then the ability to move and slip relative to grout improves, but the anchoring stability may be compromised
Solution Approach 1:
The rock bolt structure is segmented into distinct functional zones: smooth cylindrical stem portions for movement, and anchor zones (mechanical anchor, resin anchor, grout anchor) for stable anchoring. The smooth stem portions are specifically positioned between the anchors, allowing them to move relative to the grout while the anchors themselves remain firmly anchored in the rock. This segmentation ensures that the smooth surface facilitates movement where needed without compromising anchoring stability at the anchor locations.
Solution Approach 2:
The smooth cylindrical stem portions act as intermediaries between the rigid anchors and the surrounding rock mass. These stem portions can move and slip relative to the grouted borehole surround, absorbing energy and accommodating deformation, while the anchors serve as stable connection points to the rock. The intermediary stem portions transfer forces between the anchors and the rock mass while allowing controlled movement, maintaining both ease of operation and anchoring stability.
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
Enhances rock reinforcement by providing active and passive anchoring mechanisms, effectively constraining deformation and dilation, and accommodating dynamic loads through multiple anchor points and elongate stem portions.
Implementation Method 1
a mechanical anchor or a composite anchor at, or at least partially located on, a first end portion of the body
Implementation Method 2
the second anchor is adapted to exceed the diameter of the body in at least one radial direction to be locally anchored in a grouted borehole
Implementation Method 3
each stem portion is adapted to elongate, move and slip relatively to the grouted borehole surround and, by the work done by this movement, absorb energy from the surrounding rock
Data Source
AI summary
A rock bolt includes an elongate metallic body having a first end and an opposed second end, a threaded portion at the second end, for attaching thereto and locating thereon, a nut and a bearing plate, a mechanical anchor at, or at least partially located on, a first end portion of the body and a first resistive anchor, located between the threaded portion and the mechanical anchor.