# Mining Contract: Development of Rib Brow Guideline and Integration into the Coal Pillar Rib Rating (CPRR) System

Keywords:Computer simulationMining engineering

| Contract #                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       | 75D30122C14756 |
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| 9/1/2021                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| In underground coal mines, rib instabilities remain a serious safety concern. Despite a global effort by researchers to better understand the behavior of coal ribs to improve their stability, the number of rib-related injuries and fatalities in underground coal mines in the United States has remained steady over the last decade. To address this problem, NIOSH researchers have developed a new engineering-based rib classification method, the Coal Pillar Rib Rating (CPRR) system, which in its current form estimates the stability of solid coal ribs using a set of empirical field observations and synthetic data generated by computer simulation using what is termed the coal-mass constitutive model. This model has been effective for simulating stress-driven failures, but the failure of coal ribs with rock or strong coal units and the formation of brows (which is the area at the top of a coal shaft) is a complex mechanism. Rib failures result from a combination of both kinematic and stress-driven failures, the modeling of which is best suited for distinct element-based solutions that can efficiently handle the simulation of both the intact rock/coal units as well as the explicit bedding planes and cleat/joint systems. Ongoing improvements to the CPRR system convert the coal-mass constitutive model from its current form to the distinct element-based solver (3DEC) form, with promising results that can realistically simulate kinematic and stress-driven failures as well as a combination of the two. As this research advances, the ultimate goal is to develop a set of intuitive, user-friendly charts and tables that mining engineers and mine operators can use to estimate the stability of the coal rib brows found in their unique mining conditions. |
| - Geologic Characterization
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## Contract Status & Impact

This contract is ongoing. For more information on this contract, send a request to mining@cdc.gov.

The primary objective of the research under this contract is to enhance the safety of miners through new brow management strategies. To achieve this goal, the tasks outlined below will be undertaken.
        - Analysis of the available data on injuries and fatalities caused by coal brow failures around the world compared with U.S. data.
        - Identification of brow formation mechanisms in coal ribs.
        - Stability assessment of formed rock and hard coal brows by estimating the factor-of-safety of the formed brow (BrowFOS) through the combination of field data and numerical simulation results.
        - Investigation and evaluation of the effectiveness of different support systems to enhance brow stability.
        - Integration of BrowFOS analyses and management strategies into the CPRR system by the development of a set of intuitive and user-friendly charts and tables.

This work will be done in collaboration with the Missouri University of Science and Technology (Missouri S&T), with a Missouri S&T research team that has developed the capability to model not only stress-driven failures, as did the previous form, but also the failure along explicitly introduced discontinuities. The mechanical behavior of the coal rib in the newly developed models has been calibrated by comparing the rib factor of safety values derived from the original NIOSH CPRR models and models developed by Missouri S&T.

It is expected that the outcomes of this research will help to reduce the severity and frequency of rib brow failure-related injuries and fatalities via the development of intuitive and easy-to-use rib stability and BrowFOS analyses and management strategies. Achievement of this goal will further the understanding of the effect of support elements on rib brow prevention and stability for a wide range of coal mining conditions.

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July 10, 2023

July 10, 2023

National Institute for Occupational Safety and HealthMining Program

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