Semester

Fall

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mining Engineering

Committee Chair

Deniz Tuncay

Committee Member

Ihsan Berk Tulu

Committee Member

Vladislav Kecojevic

Abstract

The room and pillar mining method is the most commonly utilized method for extracting minerals found in flat-lying stratiform, and it has been used in the majority of underground stone mines in the United States (Esterhuizen et al., 2011), as a consequence, it is a primary topic of study in the mining field. If a set or layout of pillars is unstable, it can cause a major collapse, resulting in not only the destruction of the underground mine, but also air blast, subsidence, and convergence of the mine opening, especially if they occur in a short period of time (Esterhuizen et al., 2011).

Much research has been conducted in recent years to address the pillar failures that are occurring in the Eastern and Midwestern United States. Esterhuizen et al. (2011) developed the software S-Pillar, which is the foundation for underground stone mine pillar design today, based on a statistical examination of 34 underground stone mines in the United States. The outputs of this software include recommended width-to-height ratios, pillar strength, and Factor of Safety. Because S-Pillar software provides statistics on how well a certain arrangement of pillars is operating, the industry has increased its use (Rumbaugh et al., 2022). However, there is still room for improvement that will allow industry to take full advantage of it.

In this research a numerical simulation is performed to gain a better understanding of the brittle behavior. The implementation of the S-Shaped failure envelope, proposed by Kaiser and Kim (2015), is implemented by varying the strength parameters of the rock mass using a linear relationship to calculate the cohesion and friction angle with respect to the minimum principal stress 𝜎 3 )). The strength of the underground stone mine pillars is estimated using the Finite Difference Method software FLAC3D, developed by Itasca Consulting Inc. The approach is carried out by considering the previous statistical studies on the S-Pillar parameters and previous implementations of the brittle behavior in underground stone mines, using procedures similar to those used by Esterhuizen (2007), Sinha & Walton, (2017), and Sears et al., (2019). Five cases are studied with varying width-to-height ratios of 0.5, 0.8, 1.0, 1.5, and 2.0, and the resulting strength is compared to the empirical equation derived by Esterhuizen et al (2011). In addition, the influence of inclination is investigated by modeling half pillars with 15 degrees of seam inclination for the same five width-to-height ratio cases. The brittle nature of the stone pillars was successfully captured and will help us better understand the failure mechanism of the pillar collapses.

Embargo Reason

Publication Pending

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