Nonex can be used to do mass breaking including shaft sinking through the application of a specific methodology

Guiding Principle

The pressure of expanding gasses breaks rock in tensile > the free face burden. A mass break is created when multiple holes are drilled vertically and charged with a large number of heavily charged cartridges such as 500g x 60mm diameter Nonex 50060 (drilled using a rig). The free face becomes the surface cap above the charged holes. Depending upon the nature of the rock, it is feasible to drill to a depth of 2m with spacing of 1m, charging up to 300 holes, on a bench 40m x 7,5m..300 x 500g cartridges initiated simultaneously produce 150,000 litres of gas, which must go somewhere. This combined volume of gas takes off the cap, shattering it into small particle sizes. Noise and fly rock is controlled by a layer of conveyor belting mats over the charged bench and up to 2m of earth cover on top of the mats.

Practical Hints

• A mass initiation of this size requires serious planning and attention to detail; the circuit resistance for 300 cartridges will be in excess of 150 ohms, measured on an ohmmeter, requires a high capacity shot firer like AECE 1224 (otherwise there will be misfires)
• Mass rock breaking requires the support of an excavator, preferably 30t +capacity, to dig out the broken rock, as well as to cover the charged bench from the edge. (reach 7,5m, unless covering from both sides)
• The covering process risks breaking the wiring. Use an ohmmeter with an alert charge hand in control. His job is to note exactly where and when continuity was broken, call a stop and point to the recovery spot; otherwise it is an almost impossible time-consuming task, like looking for a needle in a haystack.
• In shaft sinking however, the shaft diameter only permits access to small excavators with a small capacity bucket,, or to a grapple handled by a tower crane, so the drilling depth must be reduced to say 1,5m maximum and the spacing to about 0,5m in order to create smaller fragmentation for loading
• As the shaft gets deeper, the use of earth cover becomes expensive and time consuming. The solution is to construct a steel deflector shaped like a saucer, designed to be held in place over the mouth of the shaft on initiation in order to deflect fly rock back into the shaft bottom
• As the shaft descends, ground water will enter from the sides, requiring water-resistant cartridges. Waterproof connections in the wiring-up process are essential. High capacity shot firers deliver more than 1000 volts, which will short out due wet connections and cause massive misfires.
• Insulation tape with bitumen works but is dependant on the charge hands finger dexterity ; the best solution is to use 3M UY2 connectors designed for telecommunications;. a crimping tool designed to regulate pressure is essential. A very strong, waterproof connection is provided at relatively low cost. Locating a break in a shaft containing water is challenging. The wires to be reconnected must first be dried to avoid shorting and resultant misfires
• Stemming materials and stemming techniques are crucial, otherwise the gas escapes through the drill holes by attacking the stemming. -5mm crusher dust is a benchmark in dry holes, a mix with 13mm aggregate works best in wet holes. Tamping with broken drill steels adds weight and speeds up compaction (is safe with Nonex cartridges) Pneumatic , stainless steel stemming loaders are available to blow crusher dust into horizontal holes; compacts automatically due speed of entry under pressure.