Overlapping Cable and Friction Bolts for Immediate Ground Support
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Solution Overview
Problem
Existing rock bolt installations using cable bolts require grout curing time, delaying access to reinforced tunnels, while rigid bolts provide immediate support but are limited in length, necessitating a solution that combines both for immediate and full-length reinforcement.
Innovation Solution
A rock bolt installation comprising a cable bolt and a friction bolt in an overlapping relationship, connected structurally, where the friction bolt provides immediate support and the cable bolt extends deeper, with a structural connection formed by cured grout or clamping, allowing simultaneous operation and full support upon curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If cable bolts are used for deep reinforcement, then the bolt can extend further into the rock strata, but ground support is delayed until grout curing is complete
Solution Approach 1:
The bolt system is segmented into two distinct components: a cable bolt for deep anchorage and a friction bolt for immediate shallow support. The friction bolt provides instant ground support at the tunnel face while the cable bolt extends deeper into the rock strata. This segmentation allows both immediate and long-term support functions to be fulfilled simultaneously, resolving the contradiction between bolt length and time to effective support.
Solution Approach 2:
The friction bolt performs preliminary ground support action immediately upon installation, before the grout curing process is complete. By providing initial support through friction engagement, the system eliminates the waiting period that would otherwise be required for grout curing, allowing personnel to access the tunnel sooner while the cable bolt continues to develop full capacity as grout cures.
2Loss of time
If rigid bolts are used for immediate support, then ground support is provided immediately, but the bolt length is limited by tunnel dimensions
Solution Approach 1:
The system merges the immediate support capability of rigid friction bolts with the extended reach of flexible cable bolts into a single integrated installation. The friction bolt component provides immediate ground support through friction engagement, while the cable bolt component extends deeper into the rock strata beyond what a rigid bolt could achieve. This merging allows the system to simultaneously achieve both immediate support and greater bolt length.
3Device complexity
If a single bolt system is used, then the installation is simpler, but it cannot provide both immediate and full-length reinforcement simultaneously
Solution Approach 1:
The dual-bolt system performs multiple functions within a single installation process: the friction bolt provides immediate shallow ground support while the cable bolt provides deep long-term anchorage. This multi-functionality allows the system to deliver both immediate and sustained reinforcement capabilities that a single bolt system could not achieve, while the integrated installation approach keeps the added complexity manageable.
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 immediate ground support during grout curing, with enhanced stability and load distribution, allowing safe and timely access to reinforced areas, and full support once grout cures, overcoming the limitations of single-bolt installations.
Implementation Method 1
the friction bolt exerts clamping pressure against the cable bolt to clamp the cable bolt against an internal surface of the hole
Implementation Method 2
the cable bolt and a friction bolt disposed within the hole, the cable bolt optionally being embedded in the grout, cement or resin
Data Source
AI summary
A rock bolt installation for a hole formed in a rock strata includes a cable bolt and a friction bolt disposed within the hole. The cable bolt can be embedded in grout, cement or resin. The cable bolt extends further into the hole than the friction bolt. The cable bolt and the friction bolt are disposed in an overlapping relationship within the hole and are connected structurally in the overlap to each other and to the internal wall of the hole.