A New Method of Repairing Stream Channels.
Ackman-TE; Jones-JR; Hustwit-CC
Proceeds: Coal Mng Tech Economics & Policy Am Min Congr PP 201-230 :30 pages
A new approach to identify and subsequently seal surface infiltration zones was evaluated by the U.S. Bureau of Mines at two streams that partly overlie abandoned coal mine workings and an active longwall mine. Electromagnetic terrain conductivity surveys were performed within the stream channels to identify water- saturated zones, presumably associated with fractures, at relatively shallow depths between 10 and 50 ft (3 and 15 m). Zones of increased conductivity were generally found to be positively associated with areas exhibiting significant loss of flow. Conversely, zones that exhibited reduced conductivity delineated areas where flow losses were not present. Using this information, an experimental grouting procedure was used to inject expandable polyurethane grout a few feet (less than 1 m) beneath the streambeds across the loss zone. The grouting efforts resulted in a 95- to 100- pct flow recovery. The conductivity surveys represent a significant time and cost savings when compared to conventional full-year gaging work typically necessary for delineation of stream loss zones. Conductivity data also resulted in the accurate prediction of a loss zone prior to longwall mining at one site. The economics of grouting were determined to range from comparable to half the cost of conventional stream-sealing techniques.
Proceeds: Coal Mng. Tech., Economics & Policy. Am. Min. Congr., PP. 201-230