Semester

Spring

Date of Graduation

2020

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mining Engineering

Committee Chair

Yi Luo

Committee Member

Qingqing Huang

Committee Member

Brijes Mishra

Committee Member

Victor H. Mucino

Committee Member

J. Drew Potts

Committee Member

Rudy J. Matetic

Abstract

Roof bolting has been the primary means to improve mine safety in the aspect of preventing different types of roof falls in underground mines. However, based on the published researches, underground roof bolting operators exhibit a continued risk for overexposure to high levels of respirable coal and crystalline silica dust from the roof drilling operation. Inhaling these dust can cause coal workers’ pneumoconiosis (CWP), also known as black lung. Another job-related lung disease silicosis, a disabling and even fatal and irreversible illness, could be developed through overexposure to quartz-laden dust. A recent NIOSH research shows that the quartz content in the total roof bolting dust can be as much as 50% and 20% of them are 5 µm or smaller in size. Dust in this size range is even fatal because the chance for them to reach the gas-exchange region of the lung and being deposited increased dramatically. Therefore, rock drilling in roof bolting operation could be the major quartz source for causing silicosis to this group of underground miners. Even with engineering controls and federal regulations in place, new cases of black lung and silicosis continued to be reported and seen in young miners.

This research is focused on the development of controlled drilling technique for roof bolt drilling dust reduction purpose. It can be an important approach to reduce the harmful dust from its generation source. Different from conventional passive engineering controls, this approach is a proactive one that can cut down the generation of harmful dust from its source.

A bolt-hole drilling mechanical model, as an analytical tool to identify the most influential drilling parameters to the energy consumption and dust generation was developed. Laboratory drilling tests were conducted to validate the mechanical model and the dust samples were collected and analyzed to investigate the relationship between the cumulated respirable dust productions with different drilling bite depths. The effect of bit wear, bit size and rock material on dust generation and energy consumption was evaluated as well. The generated respirable dust was mainly collected by the pre-cleaner and dust-bag.

The effect of drilling bite depth on energy and dust generation was analyzed for all the tests. An exponentially decreasing trend was observed between drilling specific energy and bite depth. While the dust generation characteristics showed a considerable reduction in both inhalable and respirable dust generation rate when increasing bite depth from 0.15 to 0.60 cm/rev (0.059 to 0.236 in/rev).

An integrated drilling control algorithm for respirable dust reduction, operation safety, as well as energy conservation was developed based on the test results. This algorithm is able to determine the rational bite depth range by monitoring the drilling specific energy in real time. When drilling a particular rock at its optimum bite depth, the energy efficiency is highest, the generation rate of fine dust is maintained at a lower level, the chances of bit clogging is greatly reduced and steel buckling is prevented. This algorithm can be incorporated into the existing drill control unit on roof bolters. As this developed drilling control algorithm does not sacrifice productivity or need extra labor to achieve its dust reduction goal, it can also benefit the industry economically while improving the occupational health and safety condition.

Embargo Reason

Publication Pending

Available for download on Friday, September 03, 2021

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