Periodically it is necessary to measure fluid pressures in an underground mine or tunnel. The reasons for undertaking such work are generally do determine the need for or effectiveness of mine drainage for water or gas.
Sigra generally use two types of system for this purpose. The first is packer based using single or multiple packers while the second is based on cementing (grouting) a hole and using the cement displacement techniques to connect capillary tubes to the hole collar. These may then be connected to pressure transducers or gauges. In addition to these similar techniques as adopted for surface holes may be used for holes that are inclined downwards.
Figure 1 shows a multi-packer system used to monitor pressure in various sections of a borehole while Figure 2 shows the cemented (grouted) equivalent.
Figure 3 shows a typical application where a central hole in a coal seam is fitted with a pressure sensing system such as that shown in Figure 1 or Figure 2 and has four flanking holes drilled parallel to it to for drainage.
Figure 1.Multi-point packer system to monitor pressures in borehole.
Figure 2. Multi-point cemented in pressure sensing system for a borehole
Figure 3.Typical use of multi-point pressure sensing to monitor drainage.