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Consolidation of bad top at the Virginia Pocahontas Division of Island Creek Coal Company.

Von Schonfeldt HA; Pothin R
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, Contract-ET-78-C-01-3271, 1979 Jan; :1-87
A test was conducted to stabilize broken roof rock (bad top) in the Beatrice Mine of the Beatrice Pocahontas Company. The technique was originally developed in Europe and is based on injecting polyurethane into the friable roof strata through a pre-determined number of drill holes. Upon curing, the polyurethane re-cements the rock fragments into place and forms a consolidated mine roof. The tests were carried out in the headgate entry of a longwall system. The objective of this work was to demonstrate that polyurethane could be successfully used to prevent roof falls in an area that would otherwise be difficult to support and thereby provide a cost effective means of maintaining an essentially uninterrupted longwall operation. A total of 10.7 tons of polyurethane was forced into the rock through 60 boreholes drilled into the roof. The test was completed approximately 3 months before the mining front passed through the consolidated area. Continued monitoring of the roof in the test area indicated that the roof had been sufficiently stabilized and that no significant roof falls were eminent. When the mining front moved through the test area, no slowdown of the longwall productivity was experienced. The longwall productivity in the 200 foot long test area actually increased approximately 35% over the average productivity prior to reaching the test area. The demonstration test therefore was regarded successful in preventing a major roof fall in a highly unstable area and in maintaining average or better longwall mining productivity. It was found that chemical consolidation is particularly well suited for applications around longwall systems because the method has the potential of maintaining high longwall production even under difficult ground conditions.
Mine roadways; Polyurethanes; Roofs; Underground mining; Injection; Longwall mining; Stabilization
Publication Date
Document Type
CP; Final Contract Report
Fiscal Year
NTIS Accession No.
NTIS Price
Identifying No.
NIOSH Division
Source Name
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, Contract ET-78-C-01-3271
Performing Organization
Occidental Research Corporation
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division