Sliding Anchor with Tangential Recesses for Breakaway Force Control
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Solution Overview
Problem
Conventional rock bolts fail to provide precise and repeatable yield force, leading to unpredictable load transfer and potential collapse in tunnel or gallery stabilization, as they lack a mechanism to control the breakaway force effectively.
Innovation Solution
The sliding anchor design features recesses in the sliding body cage that are tangentially arranged to the anchor rod, allowing sliding bodies to fill the cross-section precisely, enabling precise control of the clamping force and ensuring repeatable breakaway performance without material deformation, by using sliding bodies with greater hardness than the anchor rod.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional rock bolts are used, then the structure is simple, but the breakaway force cannot be precisely controlled and varies uncontrollably during yielding
Solution Approach 1:
The sliding body cage is segmented into multiple recesses (at least three) distributed around its circumference, each receiving a sliding body that contacts the anchor rod. This segmentation allows the total clamping force to be precisely controlled by adjusting the number, position, and dimensions of individual recesses, enabling accurate breakaway force setting while maintaining a relatively simple overall structure
Solution Approach 2:
Each recess is designed with specific local geometric properties (tangential arrangement to the anchor rod, predefined projection into the through-opening cross-section) to optimize the force transmission at that location. This local quality control ensures that the clamping force is precisely determined by the recess geometry rather than varying during operation
2Reliability
If sliding bodies are used to control breakaway force, then the breakaway force can be controlled, but material deformation occurs on the sliding bodies and sliding body cage
Solution Approach 1:
The material hardness parameter of the sliding bodies is changed to be greater than that of the anchor rod. This parameter change ensures that during operation, only the anchor rod deforms while the sliding bodies and cage remain dimensionally stable, preventing changes in the recess geometry and ensuring repeatable breakaway force
Solution Approach 2:
The recesses are designed as precise geometric copies or templates that define the clamping force. By making the recesses tangential to the anchor rod and having them project a predefined amount into the through-opening cross-section, the force transmission geometry is precisely replicated, ensuring consistent breakaway behavior
3Ease of operation
If the recesses are arranged radially to the anchor rod, then the structure is simple, but the clamping force cannot be precisely determined and varies during operation
Solution Approach 1:
The recesses are arranged asymmetrically relative to the through-opening, specifically tangential to the anchor rod rather than radially symmetric. This asymmetric arrangement, where the central longitudinal axis of each recess is skewed to the central longitudinal axis of the anchor rod, creates a precise geometric relationship that determines the clamping force, while still maintaining ease of installation
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 design allows for precise and repeatable control of the breakaway force, distributing loads evenly and preventing material deformation, ensuring stable rock bolt performance and predictable behavior under varying loads.
Implementation Method 1
The prerequisite for this is, of course, that - as already cited in the state of the art - the material hardness of the sliding body is greater than that of the anchor rod
Implementation Method 2
Since the enveloping surface of each recess in the sliding body cage provided for receiving a sliding body protrudes a predefined amount into the free cross section of the through-opening of the sliding control element, the clamping force with which the sliding body or sliding bodies hold the anchor rod extending through the through-opening can be very precisely determined with the help of this dimension be preset
Data Source
Figure 1
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AI summary
The invention relates to a sliding anchor (10) for inserting in a borehole. The sliding anchor (10) has an anchor rod (12) on which is arranged a sliding control element (14) with a through opening (18) through which the anchor rod (12) extends. The sliding control element (14) comprises a sliding body cage (16) which has at least one cutout (20) for accommodating a sliding body (22) which is in contact with the outer surface of the anchor rod (12). In order to set a predefined breakaway force in a precise and accurately reproducible manner, each cutout (20) is arranged tangentially to the outer surface of the anchor rod (12) for the purpose of accommodating a sliding body (22) in the sliding body cage (16). Furthermore, the outer enveloping surface of each cutout (20) protrudes by a predefined amount into the free cross section of the through opening (18), and each sliding body (22) completely fills the cross section of the cutout (20) associated therewith.