Numerical modeling of coal wall spall in a longwall face

• Longwall face spall mechanism was revealed numerically and verified by field observations.
• Mechanical behaviours of coal wall were presented versus longwall face advancing.
• Tensile stress concentration near the coal wall dominates the tensile splitting failure as laminas after coal wall exposed.
• Shear strain bands initiating from the outer ends of tensile areas results in shear slipping failure as blocks subsequently.