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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.

Entry link: Watergel


A Work Breakdown Structure (WBS) is a way of visualising complex processes and projects into simplified elements.


There are a few rules rules for the development of a WBS

100% rule

An important design principle for work breakdown structures is called the 100% rule.[14] It has been defined as follows:


The 100% rule states that the WBS includes 100% of the work defined by the project scope and captures all deliverables – internal, external, interim – in terms of the work to be completed, including project management. The 100% rule is one of the most important principles guiding the development, decomposition and evaluation of the WBS. The rule applies at all levels within the hierarchy: the sum of the work at the "child" level must equal 100% of the work represented by the "parent" and the WBS should not include any work that falls outside the actual scope of the project, that is, it cannot include more than 100% of the work… It is important to remember that the 100% rule also applies to the activity level. The work represented by the activities in each work package must add up to 100% of the work necessary to complete the work package.[15]

Mutually exclusive elements

Mutually exclusive: In addition to the 100% rule, it is important that there is no overlap in scope definition between different elements of a work breakdown structure. This ambiguity could result in duplicated work or miscommunications about responsibility and authority. Such overlap could also cause confusion regarding project cost accounting. If the WBS element names are ambiguous, a WBS dictionary can help clarify the distinctions between WBS elements. The WBS Dictionary describes each component of the WBS with milestones, deliverables, activities, scope, and sometimes dates, resources, costs, quality.


Plan outcomes, not actions

If the work breakdown structure designer attempts to capture any action-oriented details in the WBS, the designer will likely include either too many actions or too few actions. Too many actions will exceed 100% of the parent's scope and too few will fall short of 100% of the parent's scope. The best way to adhere to the 100% rule is to define WBS elements in terms of outcomes or results, not actions. This also ensures that the WBS is not overly prescriptive of methods, allowing for greater ingenuity and creative thinking on the part of the project participants. For new product development projects, the most common technique to ensure an outcome-oriented WBS is to use a product breakdown structure. Feature-driven software projects may use a similar technique which is to employ a feature breakdown structure. When a project provides professional services, a common technique is to capture all planned deliverables to create a deliverable-oriented WBS.[16] Work breakdown structures that subdivide work by project phases (e.g. preliminary design phase, critical design phase) must ensure that phases are clearly separated by a deliverable also used in defining entry and exit criteria (e.g. an approved preliminary or critical design review).


Level of detail

One must decide when to stop dividing work into smaller elements. For most projects a hierarchy of two to four levels will suffice. [17] This will assist in determining the duration of activities necessary to produce a deliverable defined by the WBS. There are several heuristics or "rules of thumb" used when determining the appropriate duration of an activity or group of activities necessary to produce a specific deliverable defined by the WBS.


The first is the "80 hour rule" which means that no single activity or group of activities at the lowest level of detail of the WBS to produce a single deliverable should be more than 80 hours of effort.

The second rule of thumb is that no activity or group of activities at the lowest level of detail of the WBS should be longer than a single reporting period. Thus if the project team is reporting progress monthly, then no single activity or series of activities should be longer than one month long.

The last heuristic is the "if it makes sense" rule. Applying this rule of thumb, one can apply "common sense" when creating the duration of a single activity or group of activities necessary to produce a deliverable defined by the WBS.

A work package at the activity level is a task that:

  • can be realistically and confidently estimated;
  • makes no sense practically to break down any further;
  • can be completed in accordance with one of the heuristics defined above;
  • produces a deliverable which is measurable; and
  • forms a unique package of work which can be outsourced or contracted out

Converting a WBS to a Process Flow Chart

For a typical WBS the third level of detail can be used as the basis of a process flow chart.

Activities from multiple levels should not be mixed in a flow chart and the second level is usually at too high a level of detail.

Entry link: WBS

Wedge Failure

Wedge failures involve a failure mass defined by two discontinuities with a line of intersection that is inclined out of the slope face

wedge gloss

Entry link: Wedge Failure

Weight Strength

The explosive strength of a unit mass of an explosive material expressed against a standard reference, e.g. ANFO. (See also bulk strength.)

Entry link: Weight Strength

Wet Hole

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.

water 6m

Entry link: Wet Hole

Wet Wall

Wet wall in a blast hole is a condition where there is water running on the blast hole walls above the toe or any other standing water.

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.

wet wall

Entry link: Wet Wall

With Warning Explosion

An explosion which occurs as a consequence of some other cause which would be obvious to an observer in the vicinity. (Two examples of obvious causes are large fires, or large amounts of fumes coming out of an ANE tank.)

Entry link: With Warning Explosion