The other method to create a dead ends anchorage is opening the strand wires in a flared shape. This can be done by a special jack which can be seen in the pictures. These sections are embedded in the concrete and prohibit the strand from slipping in the concrete. A section of strand is gripped by the jack and is axially pushed to force the wires open up. This jack and exert 34 kN force and it weighs about 13.6 kg.
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