The objective of this research is to develop analytical approaches for assessment and prediction of the availability of longwall mining systems. After a functional analysis of longwall mining operations, the longwall production system is divided into four subsystems: coal—cutting, face—conveying, roof—support, and outby—haulage. The operating characteristics of the longwall system are then investigated based on the system configuration, component failure and repair processes, and rules of operation. Through use of the techniques of reliability assessment and stochastic systems analysis, five probability models are formulated and solved with respect to different longwall operating logic. The implementation of these models is demonstrated with a number of case studies. Furthermore, three important applications of the results have been identified for improvement of longwall performance: analysis of component importance, assessment and prediction of productivity, and optimization of system operational effectiveness. This investigation provides a systematic methodology for evaluation of longwall operational effectiveness. A number of system effectiveness measures have been developed for longwall systems with various operating characteristics. Some of the measures include system availability, reliability, failure rate, mean time to failure, mean time to repair, the expected average of the number of system failures, and the limiting probabilities of system failure due to any subsystem. Explicit expressions of system availability are obtained for several practical cases. The methodology developed can be used as both an assessment tool and a design tool for improvement of the operational effectiveness of longwall mining systems. / Ph. D.