Geotechnical charcterization of coal refuse for use as a backfill material

Both active and residual mine subsidence resulting from underground coal mining have caused surface damage to land and structures. A method of subsidence mitigation successfully used abroad, and to a much lesser extent in U.S. coal mines, is backfilling. In addition to the possible benefits of subsidence mitigation, backfilling has the potential to increase coal recovery, enhance ventilation control, and to minimize mine fires. Backfilling can also be used as a means of mine refuse disposal, provided the refuse is a suitable fill material.

A Iiterature review has been made of the various backfilling practices and stowing materials that have been used in both underground hardrock and coal mines. The mechanics of fill support were also reviewed, as well as how the physical properties of a stowing material affect its ability to provide ground support. Based on this review, a testing program was conducted to examine properties of coal refuse which are pertinent to its placement and its ability to act as a ground support material. The testing program consisted of the slake durability test, plasticity test (Atterberg's Limits), grain-size analysis, standard Proctor compaction test, falling-head permeability test, and triaxial compression test. Based on the geotechnical properties of the refuse which was sampled, it was determined to be inadequate as a backfill material.