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

• 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.