Cleat and Fracture Systems in Coal with Implications for Strength, Hydrofracking, and Gas-Water Flow Mechanisms: A Critical Review.

The cleat is a characteristic structural feature found within coal lithotypes, often in a regular pattern. The presence of cleats and fractures in coal is advantageous for miners, as they provide weak planes that aid in extraction. However, the stability of pillars and roofs relies on factors such as cleat/fracture orientation, spacing, and intensity.