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Effects of horizontal stress related to stream valleys on the stability of coal mine openings.

Authors
Molinda-GM; Heasley-KA; Oyler-DC; Jones-JR
Source
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9413, 1992 Jan; :1-26
Link
NIOSHTIC No.
10011395
Abstract
The U.S. Bureau of Mines conducted an investigation to determine the nature and frequency of coal mine roof failure beneath valleys. A mechanism for this failure and suggestions for controlling this problem are presented. Hazardous roof conditions identified in some mines were positively correlated with mining activities beneath stream valleys. Mine maps with overlays of unstable roof and locations of stream valleys show that 52 pct of the instances of all unstable roof in the surveyed mines occurred directly beneath the bottom-most part of the valley. The survey also showed that broad, flat-bottomed valleys were more likely to be sites of hazardous roof than narrow-bottomed valleys. Evidence of valley stress relief was found beneath several valleys in the form of bedding plane faults and low-angle thrust faults. This type of failure, previously believed to be only a shallow phenomenon, was found at mining depths as great as 300 ft. In situ, horizontal stress measurements beneath a valley and the adjacent hillsides confirmed valley stress relief. Numerical analysis of 13 valleys overlying 1 mine property showed the effect of the valley excavation on horizontal and vertical stress.
Keywords
Mining-industry; Coal-mining; Underground-mining; Geology; Ground-stability
Publication Date
19920101
Document Type
IH; Report of Investigations
Fiscal Year
1992
NTIS Accession No.
NTIS Price
Identifying No.
RI-9413
NIOSH Division
PRC
Source Name
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9413
State
PA
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