Mining Project: Underground Stone Mine Pillar Design in Challenging Conditions

Principal Investigator	Brent Slaker - Request information
Start Date	10/1/2016
Objective	To build the framework for expanding pillar design criteria in challenging multiple-level, deep, and dipping mining environments by undertaking thorough pillar response investigations in representative conditions at case study mine sites, and by developing design criteria for these scenarios.
Topic Area	Pillar Design

Research Summary

Since 2005, fatalities related to ground control in underground stone mines have accounted for 50% of the total fatalities. The injury rate has increased significantly over the past two years. Likewise, the fatality rate in the underground stone sector has increased overall during the past decade. The risks driving these trends are likely to increase as operations mine under deeper cover with steeper dips and more adverse geological conditions.

NIOSH developed and made public the first pillar design software program (S-Pillar) for underground stone mining in 2011, which has been widely accepted and used regularly by mining operations and the Mine Safety and Health Administration (MSHA). The empirically based S-Pillar software was designed to meet the pillar design needs of the majority of the underground stone mine industry, but did not address several uniquely challenging environments. Stakeholder discussions have indicated to NIOSH researchers that these environments will likely be encountered more often at future mining operations. Analyzing case histories for the conditions outside the scope of the previous research is necessary to provide a detailed analysis of the hazards associated with these insufficiently studied environments.

This project involves five research aims, summarized as follows.

Research Aim 1. Develop an empirical database of existing limestone operations in multiple levels, deep cover, and dipping seams, and document fundamental pillar design parameters and qualitative performance assessments.

Research Aim 2. Identify study mines and conduct exploratory investigations to determine rock mass characterization, material properties, stress conditions, geologic features, and measured pillar responses at target locations that support a parametric assessment of pillar stability.

Research Aim 3. Identify pillar instability mechanisms occurring in challenging environments, such as multiple levels, deep cover, and dipping seams, and identify differences compared to instability mechanisms in less challenging environments that form the basis of current pillar design guidelines.

Research Aim 4. Develop and calibrate numerical models that replicate pillar responses and failure mechanisms and validate against case study mine observations and measured responses in challenging mine environments.

Research Aim 5. Assess global stability issues and develop pillar design criteria based on case study results that will form the basis for establishing universal design guidelines for stone mining in challenging environments, such as multiple levels, deep cover, and dipping seams.

 During the execution of the project, a number of technical papers will be published as specific milestones. Initially the research results will be presented at the annual underground stone safety seminar for each year of the project. By presenting at this seminar, it is believed that representatives from 75% of the known underground mines will be exposed to the results. In addition to the stone seminar, the results will be presented via open industry briefings and be made available to MSHA metal/nonmetal district offices if applicable. A NIOSH Information Circular on pillar design criteria in these challenging environments will be completed to distribute to all stakeholders.

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