Fracflow Summary Report
SUMMARY
of
Fracflow Consultants Inc. report of December 14, 1997
The main seepage zones, Zones A, B and C, are located along the southeast side of the mine, close to or in the abutment pillar
The drifts in Zone C, the site of the major inflow, were mined in the early 90's. Inflows started as minor seeps and major inflows were first observed in June 1997.
The development of increased seepage appears to have been related to the large size of the drifts, the mining method used and mining too close to the cap rock (within 7 to 10 m.)
Based on the long period to produce the significant changes in the inflow rates, it is clear the mine inflows are controlled by the water bearing properties of the overlying formations rather than by dissolution of the evaporates.
The higher mine inflows are assumed to reflect connection by caving along or into a fault/fracture zone(s) or an aquifer that has much higher water transmissive properties than the regularly fractured bedrock or porous media. If the caved zone continues to grow, the inflows in Zone C will continue to increase.
The initial grouting effort by the mine demonstrated that the leak from the caved zone could be plugged, even if it was only on a temporary basis.
The failure of the temporary plug in the caved zone is considered to be primarily due to the build up of high water pressures behind the plug as the seal began to form. This build-up of high water pressures was due to the failure to put in place a proper system of relief holes in the caved zone before the grouting system was started.
However, despite the apparent failure to complete the pressure relief holes, the drilling attempt did demonstrate that a properly equipped drill rig could effectively and safely drill pressure relief holes up through the back and the cap rock into or close to the caved area.
Based on the change in water inflows and the geological data provided from the two grouting holes, drilled from surface, there is a very high probability that the main conduit for the mine water inflows is a fault of fracture zone.
In order to determine if the conduit and the caved area can be sealed, the shape and the extent of the caved zone and fracture zone must be established.
Other workers have reported that gypsum does form in the overlying formations. If the inflow waters are saturated with respect to gypsum, then it may be possible to inject water saturated with calcium chloride and promote the growth of gypsum minerals in the fracture planes/zones. Gypsum will effectively seal the conduit and reduce the inflows, and permit one to then plug and seal the caved zone.
It is our opinion that the mine can be salvaged if the main conduit is a fault/fracture zone and effective pressure relief/control holes can be established followed by grouting /sealing of the fault/fracture zone.