Grouting techniques have been used for many years to solve various aspects of coal mine pollution and subsidence problems. The principal applications are in preventing roof collapse with subsequent subsidence over old mines, abating acid mine drainage from deep mines, and extinguishing underground fires burning in abandoned mines and coal refuse piles. In general, the equipment and techniques are less sophisticated and capable of higher output at lower cost than, for example, those that apply to dam foundation grouting or tunnel support grout. Grout materials in coal mine applications are primarily flyash and cement.
As with any grouting project, contract specifications must allow the flexibility to deal with underground conditions, especially increases or decreases in the grout quantities, that might not be anticipated even with an adequate pre-design exploration program.
This paper represents primarily a description of the grouting techniques that apply to the above-listed coal mine-related problems, along with guidance for the designer on significant aspects of design and engineering properties.