Testing Mechanical Properties of Rock Bolt under Different Supports Using Fiber Bragg Grating Technology

Area of Science:

• Geotechnical Engineering
• Materials Science
• Sensor Technology

Background:

• Rock bolt anchoring is crucial for ground support in civil and mining engineering.
• Accurate monitoring of axial forces in rock bolts is essential for structural integrity and safety.
• Fiber Bragg grating (FBG) sensors offer a compact and precise method for strain measurement.

Purpose of the Study:

• To investigate the axial force variations in prestressed and non-prestressed rock bolt anchors under different loading modes.
• To determine the optimal loading modes (active vs. passive) for FBG sensor-based monitoring of rock bolt anchors.
• To analyze the influence of loading conditions and anchor type on the axial force distribution within the rock bolt shaft.

Main Methods:

• Design and implementation of active and passive loading modes to simulate different anchoring mechanisms.
• Integration of Fiber Bragg grating (FBG) sensors onto rock bolt shafts for real-time axial force monitoring.
• Conducting pullout tests on prestressed and non-prestressed anchors under controlled loading conditions.

Main Results:

• For small anchoring forces (<35 kN), prestressed anchors are best monitored using active loading, and non-prestressed anchors using passive loading.
• For prestressed anchors, axial force distribution along the bolt shaft is nearly uniform (<10% variation).
• Non-prestressed anchors show significant axial force variation near the plate (<15 kN), decreasing with increased load (>20 kN).

Conclusions:

• FBG sensor technology effectively monitors axial forces in rock bolts under various loading conditions.
• The choice of loading mode is critical for accurate FBG-based force assessment, particularly for low-force scenarios.
• Understanding the axial force distribution in non-prestressed anchors is vital for interpreting sensor data near the plate area.