Abandoned mine shafts pose a significant risk to both people and property. Historically most old mine shafts were loosely filled with colliery debris or other loose material which when wet can flow out of the shaft into associated workings. This outflow may cause collapse of the shaft walls and allow a crater to develop at the surface, the area of which depends upon the thickness of superficial deposits.
It is current practice to pressure grout the contents of abandoned mine shafts. With a drilling rig erected on a suitable safety platform, the shaft is drilled to its full depth or to any desired intermediate depth. Large diameter heavy duty drill rods are used, which have sufficient internal diameter to allow grouting to proceed through the rods. This allows the shaft to be drilled and grouted in one operation without the added use of casing. When grout acceptance in achieved at a suitable pressure the rods are withdrawn in 3m stages and further quantities of grout injected until the contents are grouted from the bottom to the surface.
Occasionally an empty shaft requires treatment. In this case Groundshire will carefully fill it with granular material, which may be grouted simultaneously.
Once treated the mine shaft Groundshire will, if required, form a suitable reinforced concrete cap at or near rockhead.