Mining Project: Durable Roof Support for Underground Metal Mines

Principal Investigator	Donovan Benton - Request information
Start Date	10/1/2016
Objective	To employ state-of-the-art ground control science, in a targeted program of case studies, to develop engineering solutions for ground control hazards in western underground metal mines.
Topic Area	Ground Control Overview

Research Summary

The NIOSH Mining Program and its past affiliation within the U.S. Bureau of Mines has established a long history of pioneering research in ground support. The literature gives many examples of this work that contributed to the knowledge of rock mass rating, rock mass strength, and geologic structure and its effect on the stability of underground openings. As a result of this research, design charts were developed that indicate the range of stable mine opening spans in various ground conditions. Additional research was conducted on the use of shotcrete in weak rock mass mines, and portable shotcrete test machines were developed to measure shotcrete properties (flexural, adhesion, and early strength) directly at the mine site. These tests were used to optimize the fiber content and to compare the performance of wire mesh composites to fiber-reinforced shotcrete. This research led to a better understanding of the role of shotcrete in multiple-component ground support systems being used in the mines, thereby increasing the stability of the ground and reducing the accident risk to workers.

This project seeks to significantly reduce ground fall accidents in underground metal mines in the western U.S. These ground fall accidents are directly related to falls of ground that can be measured using the MSHA database of Non-Fatal Days Lost (NFDL) and No Days Lost (NDL). Weak blocky ground, faults, seismic activity, and highly stressed ground are only a few of the cases that lead to difficult ground control conditions in which ground falls leading to worker accidents typically occur. These concerns are addressed by taking a holistic look at ground support through the mining cycle at mines experiencing these hazards. The problem is how to improve ground support for these mine hazards using a systematic design approach to reduce accident risk to miners.

This research will focus on the more difficult ground conditions where the roof is weaker and/or the stress is higher. A major design concern is the loading and strengths associated with the overlying ground support system and its ability to withstand high-energy loads. By monitoring the load and displacement of the rock mass, more effective ground support can be selected and installed that will lead to safer working conditions for miners. Additionally, instrumentation data from both laboratory tests and field evaluations capable of reading levels and/or rates of change of ground control system movement and degradation will be utilized. These features can be incorporated into mine monitoring and can be used to warn miners of rock mass instabilities.

The major tasks of this research are as follows:

1. Design and integration of novel ground control systems using results obtained from laboratory and field testing of composite support solutions.
2. Development of advanced monitoring, sensing, and data transmission systems for improved ground control.
3. Evaluation of support installation procedures for opportunities to modernize installation equipment and implement alternative methods to prevent support degradation.
4. Field assessment and dissemination of optimal ground control strategies identified within the rest of the research project through cooperation with collaborating mines.

The major output from this research will be an engineering method to optimize ground support for the specific needs of western U.S. underground metal mines. This will lead to improved ground support in difficult mining conditions. Translation of this research to practice has potential for reducing ground falls and accidents. Research results also have the potential for improving safety in other mining sectors and related industries.

---