Mining Contract: Building Capacity and Improving Mine Safety Through Experimental Rock Mechanics

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

A roof fall involves a complex failure of rock mass that occurs in an untimely manner and can result in injuries or fatalities to miners. A large number of underground mines in the Appalachian region have laminated or stack rock, which are infamous for roof falls. Roof falls in these mines have caused fatalities and numerous injuries.

From the early 1970s until now, ground control research focused extensively on in-situ behavior of rock mass. This research identified various factors such as horizontal stress effects; orientation of entries; abutment stress; and effect of stress on roof, floor, and pillars. The efforts involved extensive in-situ instrumentation of various longwall panels and multiple entries.

Various statistical-numerical models were developed by NIOSH—such as ALPS, ARMPS, and AMSS—which have increased the predicting capability of ground control engineers. The database created with these models has provided a valuable tool for validating the outcome of mine analysis. In addition, a parallel effort was applied to developing various mathematical models simulating different aspects of longwall and room and pillar mines. Current state-of-art numerical modeling programs are extremely powerful and versatile. Their prediction capabilities have overtaken the decision-making ability of ground control engineers. The models were designed with inclusion of various micro and macro mechanisms. Macro mechanism results are interpreted in the form of principal stresses and strains. However, at the micro level, research results are unavailable.

According to the Mine Safety and Health Administration in the year 2015, one hundred fifteen injuries occurred due to roof falls. Similarly, in 2014 and 2013 more than 300 miners were injured due to roof falls. Significant efforts from MSHA, the former Bureau of Mines, and NIOSH (National Institute of Occupational Safety and Health) have resulted in decreased fatalities due to roof falls. However, the fundamental mechanisms behind untimely roof falls are still unknown. The following areas have been identified for further research into what contributes towards untimely roof falls:

• Micro-mechanism of time-dependent failure of roof rock
• Probabilistic strength variation of rock masses
• Brittle failure of laminated rock
• Pore scale behavior of coal measures under triaxial stress conditions

The research will investigate roof fall in coal measures through a series of tasks, which will include reviews of published literature, extensive laboratory tests, stochastic or statistical analysis phase, data analysis, and numerical models.

Anticipated or confirmed graduate research thesis/dissertation titles include:

• Fundamental Mechanism of Time-Dependent Failure in Shale
• Shale Characterization and Size-effect study using Scanning Electron Microscopy and X-Ray Diffraction
• Behavior of Laminated Roof Under High Horizontal Stress
• The Influence of Spatial Variance on Rock Strength and Mechanism of Failure
• Simulating Laminated failure in Rockmass using PFC