The cost, complexity, lack of filling space and time create challenges in the longwall backfill operation, resulting in poor subsidence control and reduced productivity. This paper proposes an automated continuous mining and continuous backfill (CMCB) method by examining its key requirements and investigates the optimum sequence of coal panel (such as drifts) excavation to ensure ground strata control at relatively high productivity. The automated CMCB adopts the highwall mining technique underground, which enables easier automation at the workface. A numerical simulation of the Changxing coal mine in China was undertaken, and five different sequences of coal excavation were investigated, using the automated CMCB excavation parameters (assuming a 4 m width cut, 5 m mining height for a 200 m long coal slice) to determine the optimum sequence of resource excavation. The plastic zones and vertical displacement across the five models were analyzed. Simulation results of the 5 m high coal seam excavation show that the odd-even slice (OES) mining sequence, which has a vertical ground displacement of 74 mm, is the most efficient excavation method, due to its effective stress redistribution and lower induced ground displacement.

The physical and thermal behaviours of supercritical CO ₂ (Sc‐CO ₂ ), brine water, acidic water, and freshwater as geothermal fluids were numerically investigated to provide better insights into their performance in enhanced geothermal systems (EGSs). First, we analyzed the hydrogeochemical (diffusive) characteristics of the fluids resulting from density changes within the reservoirs. We then performed a coupled thermo‐hydro‐mechanical (THM) analysis to investigate the fracture deformation and heat production performance. The study shows that the induced fracture deformation at the injection and production wells by Sc‐CO ₂ is less than that of the other geofluids; however, it has the highest thermal performance. This makes Sc‐CO ₂ a less viable fluid for hydraulic stimulation in EGS production. The magnitude of the fluid‐induced deformation in the injection zone was significantly higher than that in the production zone. The rock matrix saturation time by acidic water is the least; the increased residence time within the rock matrix could increase the thermal performance relative to fluids of similar thermophysical properties.