Mining Project: Alternative Mining Methods in Challenging Environments

Principal Investigator	Joseph Seymour - Request information
Start Date	10/1/2016
Objective	To reduce injuries and fatalities caused by rockburst-related ground failures in underground mines by developing an integrated, systematic approach for monitoring mining-induced seismic events, evaluating their hazard potential, and mitigating their effect on the stability of underground workings.
Topic Area	Ground Monitoring

Research Summary

Ground falls are the leading cause of fatalities in underground metal mines and an important source of lost-time injuries. Ground fall issues are typically exacerbated in deep underground metal mines because of the high ground stresses associated with mining at extreme depths, often more than a mile beneath the surface. One of the inherent ground control problems in deep underground metal mines is mining-induced seismic events or rockbursts, which occur when a large volume of overstressed rock fails in a sudden and violent manner, resulting in the instantaneous release of a large amount of accumulated energy. Mining-induced stress concentrations in sill pillars and abutments can create an increased potential for localized strain bursts, and stress changes along pre-existing faults can produce sudden movement triggering large fault-slip seismic events that cause extensive damage.

Though not all rockbursts result in injury or fatality, the complex and unpredictable nature of these events presents a major safety concern. As the deep metal mines in the Coeur d’Alene mining district of northern Idaho continue to mine at greater depths, rockbursts are becoming a more prevalent and persistent problem. To reduce the impact of these hazards on underground workers, technological advancements are needed to improve our understanding of rockbursts and to develop better methods for assessing and mitigating these problems.

This project synthesizes and expands earlier research conducted on the Ground Control Safety for Deep Vein Mines project and is based on MSHA accident and injury data collected from the collaborating mine along with the associated accident narratives and investigation reports. This background information has been augmented by on-going cooperative research at the mine and direct involvement with rockburst monitoring and mitigation issues. These research efforts, as well as the surveillance database, are being expanded to include other mines with rockburst problems.

To address the rockburst issues mentioned above, an integrated and systematic research approach will be employed that incorporates elements of standard rock mechanics practice as well as current developments in ground support technology and mine seismology. Synthesizing the information from these fields will provide a more comprehensive basis for examining the causal factors for these mining-induced seismic events. An enhanced understanding of rockburst mechanisms will in turn lead to improved methods for assessing the hazards posed by these events, the development of more appropriate dynamic ground support techniques, and innovative means of diminishing the detrimental effect of rockbursts on underground workings.

The specific technical aims of this research are as follows:

(1) refine and enhance seismic data analysis procedures to provide a better interpretation of rock mass behavior and to improve the assessment and mitigation of seismic hazards;

(2) integrate the results of conventional rock mechanics research utilizing underground instrumentation, strength property testing, and numeric modeling with the results of the seismic data analysis to gain insight into the response of the rock mass to rockburst events;

(3) quantify and compare the performance of dynamic ground support systems to improve support methods for rockburst-prone ground;

(4) develop safe guidelines for stope shutdown and re-entry before and after rockburst events, respectively;

(5) develop improved numeric modeling approaches for evaluating and reducing seismic risks; and

(6) investigate the use of alternative mining methods with mechanized mining equipment to reduce mining-induced stress concentrations and remove underground workers from potentially hazardous conditions.

The major outputs from this project research will be peer-reviewed, publically available publications presenting elements of rock mechanics, seismology, ground support, and mine design. Application of the research results at the collaborating mine will lead to improved rockburst control practices and enhancements in ground control safety, which will promote a more widespread adoption of these innovations.

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