Use of thin spray-on liners for gas management in underground coal mines

Thin spray-on liners (TSLs) are relatively thin and fast-setting materials that are sprayed onto the rock surface to temporarily support the mining excavation. TSLs have received some success as a ground support tool, due to their considerable operational benefits, with the potential to reduce mining cost. Besides ground support benefits, TSLs also show the potential to be used for gas management in underground coal mines, due to their relatively low permeability. Coal seam gas is the main cause of gas outburst and explosion incidents, and gas management is important for the safety of underground coal mining. However, little research has been conducted regarding the application of TSLs for gas management. The primary objective of this research is to investigate the performance of TSLs as a gas management tool. The performance criteria for TSLs that are examined in this thesis are: tensile strength, adhesion strength, permeability and friction factor.To investigate the mechanical properties and permeability characteristics of TSLs, a series of laboratory tests were conducted. Laboratory tensile strength and adhesion strength tests were initially conducted to determine TSLs’ mechanical properties on coal. Laboratory permeability tests were then conducted on TSL-coated coal samples to investigate the permeability characteristics of TSLs. The results show the favourable potential of using TSLs for gas management, as the permeability of the TSLs tested was found in the range of nanodarcies.The effect of using TSLs for enhancing the gas drainage efficiency was investigated with a field trial. It has been proved that the key benefits associated with the application of TSLs are the increase in the gas purity and decrease in the air contamination. Numerical simulations were subsequently performed to investigate the effect of TSL application on gas management. The model was first calibrated with the field data and sensitivity analysis was then carried out to investigate the effect of different TSL application scenarios on the gas drainage efficiency and gas emissions.Furthermore, the frictional characteristics of TSLs were investigated with the laboratory ventilation tests. The results show that the application of TSLs can significantly reduce the friction factor of the airway.The results of this research show that TSLs can be an effective tool for gas management in underground coal mines in terms of increasing gas purity and reducing gas emissions. Meanwhile, the TSL applications can bring significant economic benefits for underground coal mine operations with regards to supporting the excavations and reducing the friction factors of the airway