Use of Schmidt Hammer with special reference to strength reduction factor related to cleat presence in a coal mine

Abstract

•A new excavability classification system is suggested for coals.•A new evaluation method of Schmidt Hammer tests suggested for cleat existence.•The highest 3 Schmidt Hammer readings are the best suited for strength evaluation.•Strength reduction factor can be reliably used for excavability classification.•Excavability classes are verified by measuring laboratory specific energy.