Deformable Retainer Arms for Self-Drilling Rock Anchors
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Solution Overview
Problem
Self-drilling rock anchors are less practical for holes drilled above horizontal due to the initial anchor rod tendency to fall out under its own weight before additional sections can be coupled, making installation inefficient and less common in such orientations.
Innovation Solution
A retainer device with a body portion and deformable arms or tabs that engage the hole's inner surface to securely hold the anchor rod in place, preventing it from falling, allowing for safe and effective installation in above-horizontal holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If self-drilling rock anchors are used in holes drilled above horizontal, then installation efficiency is improved compared to traditional cable bolts, but the anchor rod falls out under its own weight before additional sections can be coupled
Solution Approach 1:
The retainer device is pre-installed on the anchor rod before drilling, and automatically engages with the hole wall upon insertion, preliminarily securing the anchor rod in place before grouting occurs. This preliminary action prevents the anchor rod from falling out under its own weight during the critical initial period.
Solution Approach 2:
The retainer device acts as an intermediary element between the anchor rod and the hole wall. It transfers the load from the anchor rod to the hole wall through its engagement arms, providing temporary support and stability during installation until the permanent grout bond is established.
2Reliability
If traditional cable bolts are used for stabilizing rock strata in above horizontal holes, then reliability of rock stabilization is achieved, but installation time and safety risks increase significantly
Solution Approach 1:
The invention merges the drilling function and anchoring function into a single self-drilling rock anchor system. The anchor rod serves both as the drilling tool (with drill bit attached) and as the final anchoring element, eliminating the separate steps of drilling, inserting cable bolt, and grouting required in traditional methods.
Solution Approach 2:
The self-drilling rock anchor is self-installing through the drill rig. The anchor rod with attached drill bit drills its own hole and installs itself into the rock strata, requiring no separate installation equipment or procedures beyond the drilling operation, thereby significantly reducing installation time.
3Reliability
If traditional cable bolts with cement grout are used, then reliable rock stabilization is achieved, but the installation process involves multiple steps and longer cure times
Solution Approach 1:
The invention changes the grout material parameter from traditional slow-setting cement grout to fast-setting resin grout. This parameter change reduces the cure time from a minimum of 12 hours for cement grout to only 5-10 minutes for resin, dramatically accelerating the installation process while maintaining reliable rock stabilization.
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
Enables efficient and safe installation of self-drilling rock anchors in holes drilled above horizontal, providing a faster installation process compared to traditional methods and reducing safety risks associated with traditional cable bolts, with potential time savings and operational advantages.
Implementation Method 1
The body portion is configured for movement relative to the anchor rod in use, and the at least one arm or tab is configured to deform so as to engage and bear against the inner surface of the hole when the retainer device mounted on the anchor rod is driven into the hole
Data Source
AI summary
The present invention provides a retainer device 1 for retaining or holding an anchor rod 11 of a rock anchor, especially a self-drilling anchor, in a hole H drilled above horizontal. The retainer device 1 comprises: a body portion 2 configured to be mounted on the anchor rod 11, and especially on an outer or external periphery of the anchor rod, and at least one locking arm or tab 6, 7 that projects from the body portion 2 in a direction transverse to a longitudinal extent of the anchor rod 11. The body portion 2 is configured for movement relative to the anchor rod 11 in use, and the at least one arm or tab 6, 7 is configured to deform so as to engage and bear against an inner wall W of the hole H when the retainer device 1 mounted on the anchor rod 11 is driven into the hole H. The invention also relates to a rock anchor system 10, comprising: at least one elongate anchor rod 11; a drill bit 12 configured for attachment to one end region 13 of the elongate anchor rod 11 for drilling the anchor rod 11 into rock strata R; and at least one retainer device 1 according to the invention described above for retaining or holding the anchor rod 11 in a hole H drilled in the rock strata R above horizontal. The invention also provides a method for installing a rock anchor.