In many cases, single strands shall be stressed at a time. For this, Mono Jacks shall be used. These jacks are light and one person can simple handle it. The force capacity on these is about 24 tonnes and 200 mm stroke is provided by them. Both strand sizes (13 or 15mm diameter) can be stressed by these jacks. All pumps can be used to activate these jacks.
Some of the applications of this instrument are:
- Measurement of deformation around tunnels.
- Monitoring rock displacement in metro stations.
- Stability assessment in shafts and mine tunnels.
- Measuring mine roof movement.
Operation and Installation
Several pins are installed around periphery of tunnel by drilling and grouting. The convergence meter is attached from its both ends to the pins and a spring loaded handle pulls the tape to remove the slack. Once the force on tape reaches a preset value, the system locks. Meters and centimeters are read from the tape and millimeters and 1/100 mm is read from the gauge. The same thing repeats in coming days or weeks and rock displacement versus time is plotted. The amount of displacement as well the rate of displacement is used as a guide to judge about the stability of tunnel
- X: Dial Gauge (B) or Digital Gauge (C
- AA: Tape length (15 or 30m