ABSTRACT
In this chapter pertinent methods on geological characterisation of the rock layers in any highwall mining site are elaborated with the help of a case example from Godavari coal basin situated in central part of India. A general geomechanical framework has been discussed by considering geology, geophysics, hydro-geology, geotechnical properties, geological structures and in-situ stresses that affect the stability of highwall slope and highwall mining excavations. The importance of these aspects in the design of highwall mining excavations is highlighted using case studies of site investigations. Explained with case examples are geological investigation methodology for acquiring surface topographical information and preparation of 3D stratigraphical model using borehole acoustic scanner. Requirement of structural mapping such as cleats, bedding planes, faults/folds, joints, fracture planes, shear zones, lineation and lineaments, intrusions and any other form of defects or cavities and its influence on structural stability is explained. Other vital input parameters to be acquired for design and numerical modelling of highwall mining extractions viz. in-situ stress, physico-mechanical properties of rock layers, and rock mass classification are explicated. The influence of hydro-geological properties on stability of geotechnical structures and the importance of using statistical methods for determination of data uncertainty are elucidated in this chapter.
