Semester

Fall

Date of Graduation

2020

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mining Engineering

Committee Chair

Ihsan Berk Tulu

Committee Member

Christopher Mark

Committee Member

Morgan M. Sears

Committee Member

Yi Luo

Committee Member

Brijes Mishra

Abstract

Floor heave—the excessive deformation and failure of floor strata—is a serious problem for many underground coal mining operations in the U.S. There is an accepted floor heave design methodology developed for the Illinois basin coal mines (Gadde, 2009). However, for Eastern U.S. coal mines in the Appalachian region, there is not any systematic design method to assess floor heave potential. In order to prevent stability problems associated with floor failure and to ensure the safety of the miners in this region, a systematic and proactive method to assess the potential of floor stability that also takes the floor failure mechanisms into consideration is a requirement. In this study, the Coal Mine Floor Rating (CMFR) system, a rock mass classification system recently developed by Mo (2019) in Australia, which provides an indicator for the competence of floor strata is applied to Eastern U.S. coal mines that intermittently experienced floor heave. Exploratory geologic drill log data, overburden maps, and mine plans were gathered in a broad database for this study. Additionally, qualitative data (failure/non-failure) on floor conditions of the mine entries near the core holes were collected and analyzed so that the floor quality, and its relation to entry stability could be estimated by statistical methods. This study found that the original CMFR classification system is not directly applicable in assessing the floor stability of Eastern U.S. coal mines. In order to extend the applicability of the CMFR classification system, the methodology is modified. A calculation procedure of the CMFR classification system’s components, Coal Mine Floor Rating (CMFR) and Horizontal Stress Rating (HSR), is modified; additionally, new parameters were included in the HSR, such as orientation coefficient, horizontal stress magnitude, and elastic modulus of the strong floor layer. The stress distribution around pillars in the vicinity of the floor failure area is further analyzed through boundary element model software LaModel. After modifying the CMFR system, a better separation of failure and non-failure cases from one another is observed and an applicable rock mass classification system capable of predicting potential floor failures in the U.S. is proposed.

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