Pressurized Grout Remote Backfilling at Aml Sites near Beulah and Zap, North Dakota

摘要

The Abandoned Mine Lands (AML) Dividsion of the North Dakota Public Service Commission (PSC) is charged with the reclamation of hazardous abandoned mine sites in North Dakota. several underground lignite coalmines were operated near the cities of Beulah and Zap, Norht Dakota, from the early 1900's until about 1955. Coal seams in this area were relatively thick and the overburden generally shallow. As these mines have deteriorated with time, deep collapse features, or sinkholes, have surfaced in many areas. These features are very dangerous, especially when they occur at or near residential and commercial areas and public roads. I nthe past five years, sinkholes have surfaced benedath a commercial building (boat dealership, lounge, and gas station0 and beneath a nearby occupied mobile home north of Beulah. Sinkholes have also surfaced near KHOL Radio Station in Beulah and in the right of way of a public road south of Zap. the AML Division has conducted several emergency sinkhole-filling projects in these areas. In 1995-97, the AML Division conducted exploratory drilling which confirmed the presence of collapsing underground mines at these site.s The remediation of these sites around Beulah/Zap will take place over several years and involve three or more separate contracts due to budget considerations. In 1997, the AML Division began reclamation at these sites utilizing pressurized grout remote backfilling. In this technique, a cementitious grout is pumped through cased drill holes directly into the mine cavities to fill them and thereby stabilize the surface from collapse. The successful contractor for Phase One of the project was The Concrete Doctor, Inc. (TCDI). This paper will concentrate on Phase One of this work performed from June through September 1997. This paper will concentrate on Phase One of this work performed from June through September 1997. This project is especially interesting because grout was pumped through holes drilled inside the occupied commercial building. Grout was also pumped through angled holes that intercepted mined workings directly beneath the structure. Several specialized monitoring techniques were used to alert contractor if any movement in the structures occurred during grouting activities. Information meetings were conducted by TCDI and PSC held with landowners, business owners, residents and road authorities before, during and after the project.