Experience With Cross Measure Boreholes for Gob Control on Retreating Longwalls.
Cervik J; Garcia F; Woodman TW
Proc 2nd U S Ventilation Symp Reno Nevada, Sept 23-25 1985 :7 pages
The surface gob hole is a common auxiliary method of controlling gob gas during longwall mining in the United States. Because surface gob holes cannot always be drilled, the Bureau of Mines is conducting studies to modify and adapt European cross-measure borehole technology to U.S. Retreating longwalls. Tests conducted where overburden is 650 ft (198 m) or less indicate up to 71% of the methane produced by the mining operation can be captured by a properly designed cross-measure system. Hole spacing should be limited to 200 ft (61 m) except on about the first 600 ft (183 m) of the longwall, where spacing should be reduced to 100 ft (30 m). More holes are necessary near the start of the longwall to capture the large quantities of methane released when the first large roof fall occurs and to prevent it from overloading the return air system.
Proc. 2nd U.S. Ventilation Symp., Reno, Nevada, Sept. 23-25, 1985, PP. 123-129