Assessment of the bearing capacity of rigid secondary support systems for gob-side retained entries based on strain energy analysis

This study investigates deformation processes occurring in secondary support systems for gob-side retained entries in coal mine extraction panels mining thin seams. The task addressed is to stabilize gob-side retained entries by improving the bearing capacity of secondary support systems to prevent roof collapses and provide safe working conditions. The comparative assessment was conducted based on an analysis of strain energy-related indicators. Underlying the study are physical models simulating filling walls, concrete blocks, and combined structures consisting of blocks with wooden interlayers. During uniaxial compression tests, the deformation capacity of each type of support system was determined; critical values of relative deformation at which the structures lose their functional performance were identified. The application of an energy-based approach has made it possible to quantify the stability limit and to predict the onset of structural failure. Experimental results showed that, under uniaxial compression, rigid secondary support systems operate under an increasing resistance mode before the initiation of failure processes. At the same time, the range of linear elastic deformation of the combined support structure is 33% greater than that of the homogeneous structure (damage initiation occurs at λb = 0.103 and λb = 0.075–0.08, respectively), which results in a delayed transition to loss of bearing capacity. The incorporation of limited yielding elements into rigid structures facilitates stress redistribution and enhances their deformation capacity. An energy-based approach to analyzing the interaction between secondary support systems and the surrounding rock mass has been proposed, based on the use of strain energy density and its components, which characterize the processes of energy accumulation and dissipation. The practical significance of this study is associated with the application of the results to substantiate the design parameters for rigid secondary support systems for gob-side retained entries in coal extraction panels mining thin seams up to 1.2 m thick