Mining Topic: Ground Monitoring

Gound monitoring

What is the health and safety problem?

Observing and monitoring rock deformations can provide information for making critical safety decisions. Generally, underground mines use observational techniques to determine roof stability which are not very efficient or accurate. Mine workers have "sounded" the rock - striking it and listening for the “drummy sounds” that signal loose rock. Other techniques include microseismic monitoring, mechanical measurement, load cells, or electromechanical roof monitors.

What is the extent of the problem?

According to Mine Safety and Health Administration (MSHA) statistics (1999-2008), falls of ground were responsible for the largest portion (26%) of fatal incidents in the coal mining industry and about 40% of fatal incidents in underground coal mining.

How is OMSHR addressing this problem?

The Office of Mine Safety and Health Research (OMSHR) is developing and applying ground monitoring methods in a variety of mines with a current focus on monitoring ground in deep coal mines. Roof monitors can provide information related to roof rock stability where geologic discontinuities or weaknesses exist in the mine roof. Over time, monitoring provides the operator with a history of the stability of the mine opening, allowing for the installation of additional support where needed or the removal of equipment and personnel from potentially hazardous situations.

What are the significant findings?

OMSHR has been involved in the research and development of several significant ground monitoring systems. Most recently, OMSHR research has led to a permissible miniaturized data logging system that is now licensed for commercial production and a seismic monitoring system in deep coal mines.

What are the next steps?

Ongoing work is focusing on monitoring the ground response to the mining of coal at depth including ground pressures, displacements, and seismicity.

Noteworthy Publications & Products

• Long-Term Stability of a Backfilled Room-and-Pillar Test section at the Buick Mine, Missouri, USA (2009-10)
  Instruments remaining in a test section of a lead/zinc/copper room and pillar mine where pillar mining had taken place 14 years before were read to monitor long-term stability and quantify time dependent behavior in the mine roof and backfill.
• Microseismic Activity Associated With a Deep Longwall Coal Mine (2002-02)
  A deep longwall coal mine was instrumented with a 3-D microseismic system to help determine the exact strata mechanics associated with rock failure, redistribution of stress and associated gob formation from the longwall.
• Monitoring Coal Mine Seismicity with an Automated Wireless Digital Strong-Motion Network (2008-07)
  This paper describes a seismic network installed in western Colorado in the vicinity of three underground coal mines, its features for user access to data, and then gives two examples of seismic events resulting in some damage to mine workings.
• Rock Damage Characterisation from Microseismic Monitoring (2001-07)
  Outlines the concepts used to correlate rock failure with microseismic events and presents examples of microseismic monitoring together with associated computer modeling of the rock failure from several mine sites.
• Roof Monitoring Helps Prevent Injuries in Stone Mines (2000-11)
  The Roof Monitoring Safety System (RMSS) is described, compared to other roof-monitoring technology, and described in context with proactive ground control plans for stone mines.
• Roof Monitoring in Limestone - Experience with the Roof Monitoring Safety System (RMSS) (2000-01)
  This paper outlines the evolution of the RMSS and how it can be used in a comprehensive, proactive ground control safety program. A case history describes the RMSS being used to evaluate a mechanical impact sealing machine at a limestone mine.
• Seismic Network Operations at a Deep Underground Coal Mining District in Western Colorado (USA) (2009-08)
  This paper describes network installation and methods used to collect, process, and distribute seismicity information collected on the surface above two longwall coal mines in western Colorado, and gives several examples of the collected data.
• Technology News 475 - Roof Monitoring Safety System for Underground Stone Mines (1998-08)
  The Roof Monitoring Safety System (RMSS) provides a safer, simple, and inexpensive means for measuring roof movement; its use in underground stone mines is described.
• Three Dimensional Microseismic Monitoring of a Utah Longwall (2001-07)
  In Utah, 3-D, full waveform, autonomous microseismic arrays were placed underground and on the surface of a longwall coal mine with overburden exceeding 750 m. Overall 13,000 seismic events, including a magnitude 4.2 event, were detected and located.