The Kempton Man Shaft Project:Application of CCP Grout as a Seepage Barrier

摘要

The Kempton Man Shaft project is one of several projects sponsored by the MarylandrnDepartment of Natural Resources Power Plant Research Program (PPRP), and fundedrnin part by the US Department of the Interior Office of Surface Mining, to demonstrate thernreplacement of concrete with coal combustion products (CCPs) as the cementitiousrnmaterial in standard geotechnical applications. The 420-foot deep Man Shaft is locatedrnin the former Kempton deep coal mine in Kempton, Maryland. Fractures intercepted byrnthe shaft at roughly 130 feet below ground surface (bgs) convey good quality groundrnwater into the shaft and ultimately to the Kempton Mine Pool, where it contributes to thernmillions of gallons of acid mine drainage (AMD) that discharge into Laurel Run. Thernproject objective was to reduce the amount of ground water lost to the mine pool byrninstalling a seepage barrier around the shaft using a cementitious grout consisting ofrn100 percent local CCPs. The CCP formula for this project was developed throughrnlaboratory tests and field adjustments to form an optimal grout mixture that combined 35rnpercent dry fluidized bed combustion (FBC) ash and 35 percent dry pulverized fly ashrn(PFA) mixed with 30 percent water (e.g., 30 pounds of water per 70 pounds of dry FBCrnand PFA). The 70 percent solids mixture created the greatest strength while stillrnmaintaining flowability of the grout mix. The seepage barrier was installed fromrnSeptember through November 2003 by pressure injecting the grout through a series ofrnboreholes surrounding the Man Shaft.