Research On Coal Body Permeability Increase And Crack Generation Mechanism Under Cumulative Blasting

Aiming at the status that it is difficult for drainage in high gas content coal seam with low permeability, deep-hole cumulative blasting technology was applied to improve permeability by increasing coal seam blasting crack, coal body permeability increase and crack generation mechanism under cumulative blasting was systematically researched. Firstly, cumulative blasting experimental site coal and rock SHPB test was carried out in laboratory. Coal and rock damage characteristics and stress-strain constitutive relation under static and dynamic load were comparatively studied. Viscoelastic damage constitutive model containing low-medium-high strain rate response was proposed. Cumulative blasting scheme was designed and field test was carried out. Borehole and blasting parameters were optimized by inspecting split and permeability increasing effect. Furthermore, based on explosive mechanics and fracture mechanics theories, coal body crack extension model of cumulative blasting was built. Aiming at different phase of explosive load, blasting crack extension direction was researched, coal body crack range computational formula was got considering cumulative charge characteristics. Finally, ANSYS/LS-DYNA was applied to built numerical model, simulate coal body splitting process under cumulative blasting, investigate crack propagating mechanism and divide coal body crack range under cumulative blasting. Through the laboratory experiment, field test, theoretical analysis and numerical simulation, coal body splitting theory under cumulative blasting was improved, which provides the basis for cumulative blasting gas drainage.