Abstract / Summary The proposed research aims at improving the understanding of dynamic failures and massive collapses in Western US coal mines with the objective of improving ground fall safety. The outcome of this research will be a significant complement to the ongoing wide-ranged research and training efforts conducted by industry and government agencies. The method of investigation will be back-analyses of large coal mine ground failures using advanced numerical modeling software. The studies will begin with a comprehensive review of the available numerical modeling software and also with an examination of significant ground failures in coal mines. The numerical modeling programs considered for the study include distinct element, particle flow code, finite difference, finite element, and boundary element based codes. The recently introduced advanced features of the distinct element models, such as Synthetic Rock Mass, Bonded Particle Model, and Random Field Modeling Technique will be evaluated for their application to dynamic failure studies in coal mines. The modeling work will include simulations of well-studied simple structures, such as laboratory test specimens, coal pillars, and mine entries. Once validated, the modeling techniques will be transferred to mining units such as room and pillar panels, retreat mining sections, and head and tailgate entries for more comprehensive studies of massive collapses and dynamic failures. With further validation and calibration from the mining units, the modeling work will move onto detailed back-analyses of massive roof collapses and dynamic failures cases. Finally, a simulated model of an active longwall mine will be developed and mined to follow the real mining advances and calibrated using the information obtained from the actual mining conditions. The findings from the case histories and their numerical modeling will be evaluated and recommendations and guidelines will be developed for numerical modeling procedures leading to safer mine design.