Environmental Engineering Reference
In-Depth Information
Figure 5.34.
Mechanical packer equipment (Coffey Partners International).
The capability of the rubber rings to expand is limited. With a sealing length of about
200 mm the formation of an effective seal in closely fractured rock is difficult. Alteration
of the test section length involves removal of the whole drill string and the addition or
removal of rods below the packer. This operation is time consuming in deep holes.
Mechanical packers do however have the advantage of fewer operational problems.
A double mechanical packer requires complete withdrawal and addition or removal of
rods below the bottom packer between each test.
It is considered that mechanical packers should only be used where other packers
are not available and results are not critical. Double packers should be avoided if at all
possible.
5.14.4.2
Water supply system
The line connecting the packer to the surface should be watertight with minimum restric-
tion to water flow. Flush coupled rods or casing are commonly used. The test water
should be clean and supplied by a pump with bypass to enable control of pressure. Dirty
