Download View - IRSST

Summary
A new technology for the measurement of axial load on rockbolts and rebars in underground
mines has been designed and developed in the laboratory. The technology is known as
SAFEBOLT (Stress And Force Evaluator in BOLTS). The SAFEBOLT system consists of three
components: 1) the SAFEBOLT device installed in the bolt head, 2) a readout unit, and 3) a
connecting cable. A special test rig was constructed in the laboratory to enable the calibration
and verification of the instrumented bolt before they are sent to the mines for installation.
Three underground mines have participated in the project, namely Doyon, Bousquet and Niobec.
Both mechanically anchored rockbolts and rebars were instrumented and installed in the field.
The SAFEBOLT instruments were successfully fabricated and installed on rockbolts and rebars
of 5 to 7 foot-long. The lessons learned from the first field trials helped to improve the design of
the instrument connector on the bolt head to sustain the severe handling during the installation,
and subsequent effects due to nearby blasting.
Field installations show that SAFEBOLT technology has the potential to become an excellent
tool for monitoring the load on bolts, as it is simple to use, reliable and has now a rugged
construction. The report highlights the features and limitations of SAFEBOLT technology. A
user’s manual is presented at the end of the report.
1