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Time-dependent Behavior of Coal Measure Rocks: Adsorption Rate and Strength Degradation.

Authors
Tandanand-S
Source
MISSING :18 pages
Link
NIOSHTIC No.
10005972
Abstract
This report presents a Bureau of Mines study on the time-dependent behavior of coal measure rocks for future implementation in stability analysis and safety evaluation of in-mine rock structures. This initial study focused on moisture adsorption rate and strength degradation of shales in Pennsylvanian coal-bearing strata in the Illinois Basin. A reaction of clay minerals in Illinois shales with atmospheric water vapor was hypothesized as the adsorption and strength degradation mechanism. Part of energy exchange between shales and the environment was attributed to a free energy controlled by pore pressure of the rock and partial pressure in the environment. The relationships between adsorption versus time and strength degradation versus moisture content were derived and correlated with the experimental data. Partial saturation at various levels of relative humidity occurs within approximately 2 weeks at room temperature. The strength of shales tested decreases linearly with increasing moisture content. When the moisture exceeds 7 pct of the dry weight, these Illinois shales become unstable. To this end, the moisture content is a good predictor of rock strength for shales.
Publication Date
19870101
Document Type
IH; Report of Investigations
Fiscal Year
1987
NTIS Accession No.
NTIS Price
Identifying No.
RI 9131
NIOSH Division
TCRC;
Source Name
MISSING
State
IL; PA;
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