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Mining Publication: Reinforcing Coal Mine Roof with Polyurethane Injection: 4 Case Studies
Keywords: Coal mining Polyurethane Roof quality Support design and selection
Original creation date: October 2008
Authors: GM Molinda
Peer Reviewed Journal Article - October 2008
Download PDF Document (0.66 MB)
NIOSHTIC2 Number: 20034612
Geotech Geol Eng 2008 Oct; 26(5):553-566
NIOSH has recently completed a study of the interaction between polyurethane (PUR) and coal mine roof in order to determine the mechanism of reinforcement, in both highly fractured rock and unfractured rock. Four case studies of PUR reinforcement are presented. At a West Virginia site, a borehole camera revealed the location of roof voids and guided the PUR injection. By injecting polyurethane into a zone from 0.6 to 1.8 m (2-6 ft.) high in the roof, a roof beam was created and ongoing intersection falls were halted. In another highly fractured roof in a western Pennsylvania mine, a total of 5.8 cm (2.3 in.) of rubbleized rock was found in a zone up to 3 m (10 ft.) into the roof. Untargeted PUR injection filled approximately 1/2 of the fractures. These two case studies showed that it is not necessary to fill up 100% of the void space to create stability. In the other two field sites, polyurethane was injected into weak, but unfractured roof. Post-injection video monitoring showed that weak bedding planes were hydraulically wedged open and polyurethane injected along bedding. The reinforcement value of this injection method is limited because of the wafer-thin layer of PUR introduced along bedding, and the lack of a PUR "webbing" which would serve as a structural framework to provide strength. It was determined that video inspection prior to PUR injection can aid in identifying the fracture zones to target, and minimize "blind" pumping and loss of PUR.
Image of publication Reinforcing Coal Mine Roof with Polyurethane Injection: 4 Case StudiesPeer Reviewed Journal Article - October 2008
Download PDF Document (0.66 MB)
NIOSHTIC2 Number: 20034612
Geotech Geol Eng 2008 Oct; 26(5):553-566
See Also
ARBS - Analysis of Roof Bolt Systems - 2.5.02
Development and Application of the Coal Mine Roof Rating (CMRR)
Diagnosing and Controlling Moisture-Sensitive Roof in Coal Mines
Effects of Stimulation Treatments on Coalbeds and Surrounding Strata: Evidence from Underground Observations
Geologic Hazards and Roof Stability in Coal Mines
The Introduction of Roof Bolting to U.S. Underground Coal Mines (1948-1960): A Cautionary Tale
Numerical Modeling for Increased Understanding of the Behavior and Performance of Coal Mine Stoppings
Performance Characteristics for Welded Wire Screen Used for Surface Control in Underground Coal Mines
Roof Span Design for Underground Stone Mines
A Spatial/Spectral Domain Microwave Coal Seam Imaging Sensor-Progress in Signal Processing
Page last reviewed: September 21, 2012
Page last updated: September 21, 2012
Content source: National Institute for Occupational Safety and Health, Mining Program
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