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A watergel explosive is a fuel sensitized explosive mixture consisting of an aqueous ammonium nitrate solution that acts as the oxidizer. Watergels that are cap-insensitive are not strictly explosives and are referred to as blasting agents. Water gel explosives have a jelly-like consistency and come in sausage-like packing stapled shut on both sides and as a bulk explosive.
Water gels usually have many different ingredients. They contain a gelatinizing agent, also known as a thickener, that modifies their consistency, ranging from easily pourable gels to hard solids. Polyvinyl alcohol, guar gum, dextran gums, and urea-formaldehyde resins are the typical gelling agents. Guar, specifically, is a gelling agent used for the aqueous portion of the water gel explosives. The primary component of water gels is monomethylamine nitrate. Monomethylamine nitrate is made of methyl methacrylate or MMA, formaldehyde and ammonium nitrate. Watergel explosives are also made of ammonium nitrate, calcium nitrate, aluminum, ethylene glycol and TNT. The proportions of these components vary depending on the desired explosiveness of the watergel.
Watergels are generally more energetic and more expensive than equivalent emulsion type explosives.
In Australia watergels are supplied by MAXAM explosives.
Wedge failures involve a failure mass defined by two discontinuities with a line of intersection that is inclined out of the slope face
A blast hole that contains any amount of detectable water.
Where water depth is recorded on a dip sheet this is the depth from the toe of the hole to top of the water.
Water depth is measured by listening and feeling for the top of the ware using a dip rope and weight. This length is subtracted to give the water depth.
For example if the top of the water is measured at 22m and the hole depth is 28m then the water depth is 6m.
This is generally related to the water table being above the toe or to perched water tables. The water does not accumulate resulting in standing water, there is a discharge path.
The main issue with wet walls is that they difficult to identify. The only way is for the blast crew to examine the dip rope after each hole and check if the tape is wet above any identified standing water. Consequently the dip rope must be dried (usually by dragging in dust) before each hole.
Where non-water-resistant explosives are loaded it is essential to identify wet walls to prevent product erosion and slumping.
Wet walls are measured from the toe of the hole to the highest wet area. Note that wet walls can not be less than standing water.
Example. The blast crew member records a 30m hole with 2m standing water but notices the tape is wet on the bottom 5m. This hole has 5m wet wall.
With Warning Explosion