Rock Bolt Paddle Angles for Grout Anchoring
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Solution Overview
Problem
Rock bolts with resin or grout anchoring face limitations in hole size and stiffness due to resin viscosity issues, leading to inefficient and costly installations, as well as potential safety concerns from voids and corrosion.
Innovation Solution
The rock bolt features radially offset paddle formations, either at 55° to 65° or 40° to 50°, and a twisted configuration to improve anchoring and stiffness, allowing for full grout interaction and reduced void formation, enabling better load distribution and resin flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rock bolt is spun through the resin with paddle formations perpendicular to rotational direction, then anchoring capability is improved, but voids and bubbles form in the resin reducing stiffness
Solution Approach 1:
The paddle formations are oriented at an angle of 30-60 degrees relative to the longitudinal axis of the rock bolt, creating an asymmetric configuration that optimizes both anchoring and resin flow. This angular orientation allows the paddles to effectively engage the resin during rotation while minimizing void formation, resolving the contradiction between anchoring strength and installation stiffness.
2Reliability
If a larger diameter rock bolt is used to maintain resin annulus specifications, then support capacity is ensured, but material efficiency and cost decrease
Solution Approach 1:
The invention changes the geometric parameters of the anchor portion by introducing angularly oriented paddle formations (30-60 degrees from longitudinal axis). This parameter change enables smaller diameter bolts to achieve the required anchoring performance by optimizing the interaction between the paddle formations and resin, thereby reducing material usage while maintaining support capacity.
3Adaptability or versatility
If the resin annulus thickness is increased, then hole size limitations are overcome, but installation stiffness decreases
Solution Approach 1:
The paddle formations are concentrated in a specific angular orientation (30-60 degrees from longitudinal axis) to create localized high-stress zones that enhance anchoring efficiency. This local quality optimization allows the resin annulus to be thinner while still achieving adequate anchoring, thereby maintaining installation stiffness even when adapting to larger hole sizes.
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 configuration enhances the load-carrying capacity and stiffness of the rock bolt, allowing for smaller diameter bolts to achieve equivalent support performance without increased material costs, while minimizing voids and corrosion risks.
Implementation Method 1
a cavitation phenomenon occurs behind the trailing face of each paddle. This is due to the viscous nature of the resin and its inability to move in laminar flow to optimally fill the area behind trailing face
Implementation Method 2
the viscous nature of the resin and its inability to move in laminar flow
Implementation Method 3
the resin is prone to turbulent flow around each paddle, creating bubbles and voids
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3
AI summary
The invention provides a grout anchored rock bolt which includes an elongate cylindrical body of a suitable material which has at least one integral anchor portion which comprises of a plurality projection, each of which extends laterally from the body in at least one radial direction, wherein the projections are consecutively serially arranged along the length of the anchor portion and wherein each projection is radially offset relatively to the preceding formation at an angle that is not orthogonal.