Effect of Stemming Length on Blast Fragmentation Stemming length plays a critical role in blast performance and the resulting rock fragmentation. The primary function of stemming is to confine explosive gases within the borehole long enough for the shock wave and gas energy to fully act on the surrounding rock mass. When stemming is optimized, more of the explosive energy is transferred into productive breakage rather than being lost as airblast, flyrock, or excessive vibration. 1. Under-Stemming (Too Short) When the stemming column is shorter than required: a. Loss of confinement leads to early venting of gases. b. Reduced energy utilization causes coarser fragmentation. c. Increased airblast and flyrock due to premature blowout. d. Higher variability in fragmentation, making downstream processes less stable. The lack of confinement prevents the explosive from fully fracturing the burden, often resulting in oversized boulders, uneven muckpiles, and inefficiencies in crushing and hauling. 2. Over-Stemming (Too Long) When the stemming column is longer than necessary: a. Energy is overly confined and may not generate adequate heave. b. Fragmentation becomes finer near the collar but may remain coarse at depth. c. Potential for poor throw and tight muckpiles if explosive energy cannot effectively mobilize the rock. d. Over-stemming can create a blast that breaks the collar region well but leaves deeper zones under-fragmented, affecting shovel diggability and crusher feed consistency. Evaluating Stemming Effect Using WipFrag for Continuous Improvement WipFrag offers a practical and data-driven way to assess how changes in stemming length influence fragmentation outcomes across multiple blasts. Because WipFrag is developed by WipWare, the pioneer in image-based fragmentation analysis and a company dedicated exclusively to this discipline, it remains one of the most reliable and trusted technologies available today. When an organization concentrates its expertise on a specific area, much like a ruler designed for a precise purpose, it naturally excels. WipWare’s long-standing focus on fragmentation analysis exemplifies this principle. How WipFrag Helps: Quantify Fragmentation Differences By analyzing muckpile or truck-loading images before and after stemming adjustments, WipFrag provides: Full particle size distribution, bounder count and trend, %fine for each blast, These metrics show whether fragmentation improved or deteriorated following stemming modifications. WipFrag fits perfectly into a Plan–Do–Check–Act process: Plan: Adjust stemming length based on modelling or previous results Do: Implement the blast design Check: Measure fragmentation with WipFrag Act: Refine stemming parameters based on performance This closes the loop and ensures that stemming design evolves with actual site conditions, geology, and production requirements.