Friction Bolt with Split Tube and Restrainer for Rock Strata
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Solution Overview
Problem
Expansion rock bolts used in rock strata stabilization are prone to ejection under excessive loading, posing safety risks due to potential failure of both the tube and bar or cable, which can lead to components being ejected from the bore with considerable momentum.
Innovation Solution
A friction bolt design featuring a longitudinally split, radially expandable tube with an expander mechanism, an elongate bar or cable, and a restrainer member that engages with the bore surface to prevent ejection by transferring loads through frictional engagement, utilizing a weakened region near the trailing end and a projection through the tube split for enhanced frictional resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If expansion rock bolts are used to stabilize rock strata, then frictional engagement with the bore surface is enhanced, but the risk of ejection under excessive loading increases
Solution Approach 1:
The restrainer member is pre-installed within the tube to provide counter-action against the harmful ejection force before it occurs. The restrainer member's projection engages with the bore surface in advance, creating a preliminary restraining force that opposes the ejection tendency when excessive loading occurs.
Solution Approach 2:
The restrainer member acts as an intermediary element between the bar/cable and the bore surface. It transfers the load from the bar/cable to the bore surface through frictional engagement, preventing direct ejection of the bar/c cable while maintaining the stabilizing function of the rock bolt.
2Reliability
If a restrainer member is added to prevent ejection, then safety is improved, but device complexity increases
Solution Approach 1:
The restrainer member is designed as a separate, modular component that can be independently manufactured and installed within the tube. This segmentation allows the safety function to be added without redesigning the entire rock bolt system, thereby limiting the increase in overall device complexity.
Solution Approach 2:
The restrainer member is designed to be passive and self-activating. It automatically engages with the bore surface through its projection when loading occurs, without requiring external control systems, actuators, or complex mechanisms. This self-service approach enhances safety while minimizing added complexity.
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 effectively prevents the ejection of the bar or cable and attached components from the bore, enhancing safety by maintaining frictional engagement with the bore surface and tube, even upon failure of the tube and bar or cable, thereby reducing the risk of injury and equipment damage.
Implementation Method 1
a restrainer member which is disposed within the tube adjacent the ring, the restrainer member extending at least partly about the bar or cable and being in engagement with the bar or cable... the projection being in engagement with the facing wall surface of the bore inboard of the weakened region
Implementation Method 2
the external surface of the tube frictionally engages the internal surface of the bore. Thus, the tube is frictionally anchored within the bore
Data Source
Figure 1~5
Figure 3~7
Figure 8~10
AI summary
A frictional bolt 40 for frictionally engaging the internal surface of a bore 32 drilled into a rock strata. The friction bolt 40 includes a circular tube 42 which is split longitudinally, and which has a leading end and trailing end and an expander mechanism within the tube towards the leading end. An elongate bar or cable 47 is disposed within the tube 42 and extends between the expander mechanism at one end and an anchor arrangement at the other end. A ring 43 is welded to the trailing end of the tube 42 and the bar or cable 47 extends through the ring 43 into connection with the anchor arrangement. A restrainer member 35 is disposed within the tube 42 adjacent the ring 43 and extends at least partially about the bar or cable 47 and is in engagement with the bar or cable 47. The tube 42 has a weakened region HAZ adjacent the ring 43 and restrainer member 35 extends longitudinally within the tube 42 past the weakened region HAZ in the direction of the leading end of the tube 42. The restrainer member 45 includes a projection 38 that projects through the longitudinal split of the tube 42 for engagement with the facing wall of the bore 32.