Po Tsang

Date of Graduation

1992

Document Type

Thesis

Abstract

The longwall mining in U.S. has continuously set both the world production and safety records over the years. In order to ensure the future success of longwall mining, continuous improvement on this new mining technology is very important. This study deals with the problems related to longwall pillar design by proposing a new pillar design method based on the "yield pillar" concept. In order to simplify the geological and mining conditions, the new pillar design method classifies the in-situ roof and floor conditions into four different categories: (1) strong roof and strong floor, (2) strong roof and weak floor, (3) weak roof and strong floor, and (4) weak roof and weak floor conditions. According to different roof and floor conditions, the new method can be used to design various types of three-entry system for longwall panel development. Comparison among different types of design indicates that the stiff-yield pillar design is the most favorable design and can be used as an alternative, especially under deeper cover. The new pillar design method is developed based on the finite element model simulation, stability study and nonlinear regression analysis. The finite element model used in this study considers the material properties and time-dependent behaviors of rock. To better organize the finite element model simulation, the orthogonal experiment design is used in this study to arrange the finite element models and proved to be very effective. Using the finite element model simulation, the functions and mechanisms of the "yield pillar" have been studied. The important variables that affect the stability of longwall entry-pillar system are identified also. In this study, the new pillar design method has been also compared with the other available longwall pillar design methods. In addition, an application example is used to illustrate the basic design procedures involved in the new pillar design method.

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