Abstract:
A salt mine shaft in the United States has suffered from troublesome groundwater inflows for many years. The shaft is an unlined, 1900-feet deep, conventionally sunk, four-compartment, rectangular-shaped shaft, equipped with conventional timber sets with 6-foot vertical centers which provide a framework for shaft guides and dividers. Timber lagging has been installed between the sets as a means of ground support. Water rings have been constructed to collect the groundwater inflows into the shaft. The water is then directed and stored permanently in abandoned workings on 4 Level. The amount of storage remaining in these abandoned workings is limited. Inflows also lead to the deposition of salt on timber cribbing at depth, which can lead to the dislodgement and damage of the skips or chippy. As such, groundwater inflows must be kept to a minimum. Three previous attempts to reduce inflows into the shaft have been partially successful. Inflow rates were initially reduced but have gradually increased in recent years with sustained peak rates up to 32 gallons per minute (gpm) recorded in January 2015. This paper summarizes the grouting works carried out during the fourth attempt, in the fall of 2020, to reduce observed inflows at 1110 feet depth using polyurethane resin, ultrafine cement grouts, and acrylic gel. Keywords: salt mine, shaft rehabilitation, polyurethane resin, ultrafine, acrylic gel