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Rock mechanics study of lateral distressing for the advance-and-relieve mining method.

Authors
Maleki-H; Dolinar-DR; Dubbert-J
Source
Proceedings of the 22nd International Conference on Ground Control in Mining, August 5-7, 2003, Morgantown, West Virginia. Peng SS, Mark C, Khair AW, Heasley KA, eds., Morgantown, WV: West Virginia University, 2003 Aug; :105-113
Link
NIOSHTIC No.
20023432
Abstract
The advance-and-relieve method benefits from lateral destressing associated with mining in laminated rocks and a high horizontal stress regime. This stress control method is based on measurements showing that occurrence of rock failure in the roof and floor of an entry (or caving of roof strata in a panel gob) results in redistribution of stresses in adjacent entries. By locating other entries within the shadow zone of the first entry (or gob), improvements in stability can be achieved. Numerical modeling proved useful in studying the basic mechanics of lateral relief while investigating the sensitivity of results to different geologic and mining parameters using controlled experiments. It was shown that failure of rocks near an entry results in redistribution of horizontal stress and shifting of the stress to higher horizons. Measurements from two mines are consistent in showing significant horizontal stress reductions in comparison with the far-field stress regime within the destressed zone. Although the far-field stress regime is very anisotropic, these measurements show near-equal secondary principal horizontal stresses, or perhaps a switch in orientation, as a result of destressing. Stress relief is achieved through lateral movement and relaxation of rocks along weak bedding planes toward adjacent caved zones (or softened zone). Because of cave geometry in the advancing panel, horizontal stress concentrations occur near the cave line both in front of the face and to the sides. The horizontal stress concentration reaches 1.7 times the far-field stress ahead of the face. This stress increase is significant and may cause structural damage in this zone benefitting from additional support. In the next advancing panel located within the shadow zone of the gob, horizontal stresses are significantly reduced in the roof (by 50%). Thus, the stability of future advancing panel can be improved through prudent layout designs and sequencing. The width of the relief zone is significantly influenced by the height of the softened (or cave zone) and rock mass properties.
Keywords
Ground-control; Underground-mining; Coal-mining; Horizontal-stress; Numerical-modeling; Control-technology; Engineering-controls
Contact
NIOSH, Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, PA 15236
Publication Date
20030805
Document Type
Conference/Symposia Proceedings
Editors
Peng-SS; Mark-C; Khair-AW; Heasley-KA
Fiscal Year
2003
NTIS Accession No.
NTIS Price
ISBN No.
0939084569
NIOSH Division
PRL
Priority Area
Research Tools and Approaches: Control Technology and Personal Protective Equipment
Source Name
Proceedings of the 22nd International Conference on Ground Control in Mining, August 5-7, 2003, Morgantown, West Virginia
State
PA; CO; WV
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