Mining Publication: Use of Surface Joint and Photolinear Data for Predicting Subsurface Coal Cleat Orientation
Coalbeds exhibit a directional permeability, with the maximum permeability oriented parallel to the face cleat. Thus, the most efficient pattern of vertical degasification holes for a coalbed is dependent upon cleat orientation. Surface joints, infrared photolinears, and ronchi grating photolinears were investigated as potential estimators of subsurface cleat orientation. Cleat orientations were measured in 18 mines in the Pittsburgh coalbed in southwestern Pennsylvania and northern West Virginia to be used as a standard against which prediction techniques would be evaluated. Two cleat systems with a strong geographic segregation were measured in the study area: n 67 deg. W - n 28 deg. E (95 deg. Separation) for the north, and n 76 deg. W - n 17 deg. E (93 deg. Separation) for the south. Directional data obtained from the three techniques investigated yielded satisfactory regional predictions of cleat orientation. Analysis of surface joints was the only technique considered sufficiently reliable on a local basis. Prediction of cleat orientation is based on the pairing of the principal directional sets into all reasonable combinations of fundamental systems. The system or systems composed of the most dominant sets nearest to 90 deg. Separation are likely to be a reliable prediction of cleat orientation. The most dominant set of the system selected is likely to be the face cleat.