ABSTRACT
The chapter summarises the accident proneness of highwall mining from 20 years record in U.S., and from the field experiences in Australia and India. Highwall mining like any other mining operations are associated with hazards. Geologic features such as faults, bedding planes and joints control or strongly influence potential highwall failure modes. The risks associated with these have been a concern in highwall mining for smooth operation under specific rock-geologic conditions. The major factors causing ground-related hazards are identified. Some past examples of highwall failure and post-failure analysis are also presented. A wide range of mitigation measures for ensuring safety during highwall mining operations are discussed. A special emphasis is given for a possible method of backfilling the highwall mined entries to stabilise the ground and to improve the coal recovery. Though yet to be tried in the field, option of fly ash as a hydraulic backfill material is discussed in detail with respect to its flowability, gain in web pillar strength, its chemistry and leaching potential. Some laboratory scale experiments conducted on fly ash as a practical backfilling material are presented.
