Abstract
Rock bolts have been widely used as rock reinforcing members in underground coal mine roadways and tunnels. Failures of rock bolts occur as a result of overloading, corrosion, seismic burst and bad grouting, leading to catastrophic economic and personnel losses. Monitoring the health condition of the rock bolts plays an important role in ensuring the safe operation of underground mines. This work presents a brief introduction on the types of rock bolts followed by a comprehensive review of rock bolt monitoring using smart sensors. Smart sensors that are used to assess rock bolt integrity are reviewed to provide a firm perception of the application of smart sensors for enhanced performance and reliability of rock bolts. The most widely used smart sensors for rock bolt monitoring are the piezoelectric sensors and the fiber optic sensors. The methodologies and principles of these smart sensors are reviewed from the point of view of rock bolt integrity monitoring. The applications of smart sensors in monitoring the critical status of rock bolts, such as the axial force, corrosion occurrence, grout quality and resin delamination, are highlighted. In addition, several prototypes or commercially available smart rock bolt devices are also introduced.
Highlights
Millions of rock bolts are being installed worldwide every year and the consumption of rock bolts continues to increase
Various non-destructive testing (NDT) techniques based on piezoelectricity have been developed over the last decades, such as Lamb wave [22,23], electro-mechanical impedance (EMI) [24,25,26], guided ultrasonic waves [27], and acoustic emission (AE) [28,29]
The basic principles of commonly used smart sensors used in rock bolt
Summary
Millions of rock bolts are being installed worldwide every year and the consumption of rock bolts continues to increase. The third type is the partially or fully grouted rock bolts that are anchored by cement or resin. The installation quality and the grouting of resin anchored bolts is considered as a critical issue by the underground mining industry. Various methods have been developed to determine the integrity of the rock bolt and a conventional approach to address this issue is the pull-out test. It is a time-consuming and destructive process. The developments and applications of the smart sensors in monitoring the critical status of rock bolts, such as the axial load, corrosion occurrence, grout inadequacy and resin delamination, are highlighted. Several prototypes or commercially available smart rock bolt devices are introduced
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