Use of Ash to Improve Strata Control in Bord and Pillar Workings

SUMMARY Ash produced from South African power stations possesses self-cementing properties when mixed with water. This material is utilized for strata control purposes in bord and pillar workings. In order to quantify the effects of ashfill on strata behaviour, the mode of failure of a coal pillar is examined and model pillar tests are described. These tests indicate that ashfill not only increases pillar strength in excess of 40 per cent, but also has a significant influence on the post-failure behaviour of coal pillars. Practical examples of the application and integration of ashfill into bord and pillar mining operations are given.