Experimental and numerical study on mechanical behavior of rock beam fracture under unloading with different thicknesses and spans in deep mining working face

• Rock beams experience multiple stress reductions after unloading, with the largest reduction occurring in the first stage. • Thickness-to-span ratio governs failure mode: greater thickness promotes shear cracks, while larger spans promote tensile cracks and arching. • Acoustic emission signals and energy increase with thickness and span, indicating more intense damage evolution. • Harder rock strata position critically controls failure: top strata cause sharp shear cracks, while bottom strata expand the failure range and induce arch-shaped cracks, informing roof support design.