Mining Contract: Ground Control Research for Improving Safety Performance in Underground Stone and Other Large Opening Mines: Design, Monitoring and Risk Management

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Contract #	200-2016-91300
Start Date	9/1/2016
End Date	8/31/2020
Research Concept	The products derived from stone mining operations are ubiquitous and essential to sustain and grow both developed and developing economies. In 2015, 1.32 billion metric tons of crushed stone was produced from 3,700 quarries and 82 underground mines, according to U.S. Geological Survey data. Crushed stone products are predominantly used as construction material but are also used to produce cement, lime, and numerous other chemical and agricultural products. Although production of crushed stone is currently dominated by surface mines, the advantages of underground mining methods are becoming more apparent to operators in light of several challenges facing the industry. These challenges include increasing regulatory pressure with respect to environmental impacts and increasing difficulty of gaining social license to operate, both of which are significantly less problematic in underground mines. These contemporary issues combined with the ever-present pressures of depletion, market competition, and tightening product specifications will continue to push stone producers toward underground reserves in the future.

Contract Status & Impact

This contract is complete.

The purpose of the research under this capacity-building contract was twofold: (1) to develop science-based design and best practices that can supplement or, where appropriate, replace current empirical approaches to ground control and mine design in underground stone mines and other large opening hard rock mines; (2) to develop a new cohort of ground control experts specializing in underground mine stability in order to ensure the future health and safety of mine workers.

In the underground mining industry, unacceptably high fatality rates are tied to ground control issues related to roof and rib collapses and pillar bursts in underground mine. Underground limestone mines in the eastern U.S. have become more common over the past decade, and typically there is less underground experience resulting in a need for more engineering, education, and training. Stone mines employ fewer miners than coal mines, but they have experienced a significant number of reportable injuries because of falls of rock from the roof or ribs. In addition, the large openings and great spans between pillars can create conditions of instability, leading to a large collapse of the roof or pillar, if the mining system is not designed properly or if pillars deteriorate over time.

Underground stone mining involves geological hazards unseen in the rest of the industry and therefore faces specialized ground control and safety challenges. In particular, pillar and roof span design are often developed based on historical evidence, trial and error, or on a case-by-case basis by rock engineering experts. These design guidelines are issued with the restrictions that the rock formation is flat-lying, is developed with the room-and-pillar method, and adheres to certain geotechnical stipulations.

In an effort to address this deficiency, NIOSH conducted and published the results of a comprehensive regional case study to minimize potential sources of roof and pillar instability. It is recognized that the ground control recommendations from this study can be implemented in a number of cases; however, many mines do not fall within the design restrictions and therefore do not benefit from the regional case study or the proposed ground control solutions such as the software program S-Pillar.

For the above reasons, further research was conducted to advance the knowledge of ground control as applied to underground stone mining safety to achieve a comparable maturity to that of other mining sectors such as coal. Underground stone mining practices are currently outpacing the state of the science and will only continue to do so as operators increase their use of underground mining methods, pursue less ideal reserves, re-enter old works, and begin to consider new mining practices never attempted before, such as re-mining pillars (i.e., secondary recovery). Research must address current deficiencies and must also proactively anticipate future ground control challenges faced by the underground stone mining industry. Under this capacity-building contract, this was accomplished by training academics, researchers, and industry professionals to use the best technology available and to educate future generations on best practices and methodologies.

In addition to training a new cohort of ground control researchers, the objectives of this contract included the following:

Identifying site-specific and broad ground control challenges for this mining community.
Developing feasible and comprehensive monitoring plans for stone and large-opening room-and-pillar mines.
Identifying novel methods for ground control assessment and characterization.
Developing a methodology for the incorporation of ground control information collected via monitoring and mapping into comprehensive risk assessment and management plans.

Anticipated or confirmed graduate research thesis/dissertation titles from this research included the following:

Improving Safety for Underground Limestone Mines Using Photogrammetry
Ground Penetrating Radar (GPR) for Karst Detection in an Underground Limestone Mine
Integrating Laser Scanning with Discrete Element Modeling for Improving Safety in Underground Stone Mines