SAP hydrogel stemming improves energy utilization and environmental performance in rock blasting

Effective blasthole stemming is often omitted in tunnel blasting because of constraints on labor, operating time, and construction efficiency, causing premature detonation gas escape and inefficient explosive energy use. Here, we develop a superabsorbent polymer hydrogel stemming method and a mechanized loading device, and evaluate their performance through material optimization, model blasting tests, and tunnel field trials. The hydrogel stemming system enables stable manual or mechanized loading after water absorption and prolongs detonation gas confinement. Compared with the unstemmed condition, it more than doubles peak tensile strain at the borehole wall, promotes crack propagation and coalescence, increases blasthole utilization by 9.95%, and reduces specific charge by 11.1%. Field application also improves fragmentation while reducing blasting noise, dust concentration, and smoke evacuation time. These results show that SAP hydrogel stemming provides a practical route to more efficient and cleaner tunnel blasting.