Development and field testing of a tension measuring gauge for cable bolts used as ground support

CIM Bulletin, Vol. 81, No. 915, 1988

P. CHOQUET and F. MILLER, Department of Mining and Metallurgy, Universite Laval Quebec, Quebec

The development and testing of a simple low-cost gauge for measurement of tension in a cable bolt grouted in a borehole are presented. Its principle is based on a resistance wire which is wound on a 70 cm length into the spiral grooves of the wire strand cable bolt. Readings are then taken by a robust automatic data logger with a several day autonomy or by a portable readout. In order to have a complete profile of tension along the cable bolt, a number of tension gauges can be installed along its length. This paper provides a description of the development and laboratory calibration of the tension gauge and addresses the two modes of loading for a cable bolt in a rock mass, namely pure tension and shearing at a joint location. In the second part of the paper, four field tests in underground and open pit mines are reported. The first test was used to substantially modify both the gauge and the readout unit principles while the other tests which are still on-going show a very satisfactory behaviour of the modified version of the tension gauge.
Keywords: Rock Mechanics, Instrumentation, Monitoring, Steel cable, Tendon, Anchor, Cable bolt, Rock support, Slope stability, Ore dilution, Mining technology, Underground mining.