Scaled Depth of Burial Explained
The article explores the concept of scaled depth of burial (SD) and its significance in mitigating environmental impacts associated with blasting activities in mining and
Blasts that lose energy retention result in additional costs, uneven breakage, noise, and increased drilling and explosives. The choice in your stemming device dramatically impacts overall downstream productivity.
We compare leading stemming plugs Varistem and StemPlug based on real-world evidence and key factors to help you choose, including cost, hole diameter, compatibility, and mechanism.
Varistem’s pricing scales with hole diameter. Prices range from approximately $1.00 to $16.13 (around R17.00 to R280.00) per plug, which enables straightforward cost management.
Official StemPlug pricing is quote-based. Retailer listings indicate a range of around $1.86 to $9.68 (around R32.36 to R169.35) per plug, depending on hole size and box quantity. Pricing can vary by size, volume, region, taxes and freight.
For most 3 to 10″ holes, both Varistem and StemPlug are priced similarly per plug.
Across size codes BP2 to BP10, Varistem fits holes from 1.75″ to 10″, each with a specified fit window.
StemPlug stemming plugs are available in sizes from 3″ to 12¼″ to match common blasthole diameters.
For sub-3″ holes , choose Varistem as it goes down to 1.75″ . For holes greater than 10″, the StemPlug extends up to 12¼″. In the 3″ to 10″ band, both Varistem and StemPlug offer similar diameter options.
Varistem is compatible with ANFO, emulsion, water gel, and heavy ANFO. Use ANFO in dry holes. In damp or flooded holes, use emulsion, water gel or heavy ANFO. Varistem also supports air-decking to reduce charge mass per hole.
The StemPlug has no published explosive-compatibility information. However, this would likely conform with most explosive materials.
Varistem has documented use with ANFO in dry holes and emulsion, watergel, or heavy ANFO in damp or flooded conditions, and it also supports air-decking for explosive savings. StemPlug does not include any explosive-type guidance.
Varistem uses a flexible, tear-resistant dip-moulded body. On firing, the first shock wave pushes the plug into the stemming, producing a short-term pressure seal in the blasthole.
Energy is directed into microfractures in the rock before the plug is destroyed, yielding stronger early confinement, cleaner fragmentation and better energy utilisation in the rock.
StemPlug acts as a wedge installed above the charge and below the stemming. It wedges the stemming material between the blasthole wall and the plug; upon detonation, the plug is driven upward and seizes in the hole, helping the stemming stay in place under blast pressure.
Both Varistem and StemPlug stemming plugs improve energy retention by acting on the stemming column. StemPlug wedges the stemming device between the blasthole wall and the plug. StemPlug claims this improves fragmentation. Varistem is driven upward to create a temporary pressure seal, resulting in improved fragmentation and reduced flyrock, noise, and airblast.
Varistem has demonstrated an 11% uplift in advance per blast at an underground platinum mine (2.46 m to 2.82 m), translating to an estimated R1.91 billion annual net benefit. Additional studies report up to 80% less flyrock, 87% better cast, 14%+ higher crusher throughput, over $10 million per year in added value, $1.45 million in waste savings, and 8% quicker loading.
Independent analyses of the Stemplug show more than 20% better fragmentation using the same explosives. The plug’s action limits venting up the hole, yielding a marked reduction in dust and noise. In cap-rock applications, it allows higher column loading, aiding fragmentation. In many applications, hole patterns may be expanded, reducing drilling and explosives costs.
Varistem publishes broader, quantified case results with documented reductions in flyrock and improvements in cast and throughput, translating into material value gains. StemPlug reports a 20% improvement in fragmentation with the same explosives, with lower dust and noise, the ability to load higher in cap rock, and the potential to widen patterns to reduce drilling and explosives costs.
Use Varistem where tight collar sealing, predictable size fit and verified productivity gains are priorities. Its fine-size ladder ensures consistent installs across a wide diameter range.
In hard-rock or high-value contexts, Varistem helps retain energy and manage fragmentation. Air-deck capability adds operational flexibility. For sub-3” holes, use Varistem.
Choose StemPlug for larger blastholes over 10” or when you want a simple wedge that sits above the charge and below the stemming, with no air-deck requirement.
Both systems improve energy retention. Selection comes down to hole size and control requirements. For sub-3” holes or when air-decking and tight fit control are essential, choose Varistem. For holes greater than 10″, consider StemPlug.
The right stemming plug ultimately comes down to pricing, accuracy, air-decking needs, and adaptability.
ERG Industrial offers in-depth advice on stemming plugs and other blasting equipment. Contact us for a quote to see how your blasting team can benefit from Varistem.
The article explores the concept of scaled depth of burial (SD) and its significance in mitigating environmental impacts associated with blasting activities in mining and
Designing a blast involves the consideration of multiple parameters, and achieving the desired blasting outcome necessitates a thorough understanding of the interplay and interdependence of
Introduction and Project Background ERG Industrial conducted a Varistem® stemming plug pilot project at a South African underground platinum mine between May 2024 and June