Assessment of cavability and categorization of coal measure roof rocks by parting plane approach

摘要

From the observations of caving of the overlying roof rock in longwall panels it can be inferred that the caving is dominated by the weak parting layers, laminated nature and massiveness of the roof rock formation. This caving process is controlled by the presence and geo-technical properties of strong beds and weak parting beds in the roof rock layers. Based on the study conducted at different coalfields over longwall panels a 'Parting Plane Approach' has been developed for identifying the parting planes in the roof along with strong and weak rock beds. The strata caving behaviour over longwall workings is manifested by local and main falls. They are governed by the thickness, rock mass strength and the induced stresses in the Caving Layer 1 or the Immediate Roof and the Caving Layer 2 or the Main Roof respectively. A software has been developed in MATLAB platform to identify the rock beds as belonging to the Caving Layer 1 and the Caving Layer 2 or the Immediate Roof and the Main Roof. A parameter, Equivalent Main Fall Span (aeq), has been introduced for classifying the overlying roof rock. In this paper the various methods for determination of aeq, viz. an Empirical method, a Mathematical approach, and a Numerical modelling based approach have been discussed along with case studies.