Fundamental Principles for Ground Engineering

Abstract

In essence, all underground mining methods are the same, comprising one or more excavations separated by pillars of rock sandwiched at some orientation between the hanging wall and the footwall. The progressive removal of rock to form an underground excavation results in a decrease in the load carrying capacity of the immediate surrounding rock mass, the creation of a void into which the rock mass can displace, and stress changes in a rock mass that is weakened by the removal of confinement. The resulting rock deformation is governed by both the structural and the mechanical properties of the rock mass and the surrounding stress environment. This chapter commences with an overview of the geological settings of underground coal mines and of the generic types of mining techniques and mine layouts utilised in the given conditions. This provides context to the basic concepts of physics and applied mechanics that control rock deformation and underpin ground engineering. The more fundamental of these are developed from first principles in the remainder of the chapter under the headings of rock mass fabric; physical parameters; material properties; rock mechanics; analysis techniques; and statics. This provides a foundation for developing the principles in more detail and applying them to mine design, stability analysis, operational practices and risk management in later chapters. Their application is not confined to underground coal mining, with many being applicable to any form of excavation made in a geological setting.