South Crofty Mine Underground 13: This page is continuing the images of drive development.
This mainly covers the use and priming of the explosives before the blasting of the face.
South Crofty Mine Underground 13.1 – Vivian Mugford is on the right of the image. The drive was very wet here with water pouring from the roof. I do not know the location, if anyone does please let me know.South Crofty Mine Underground 13.2 – The face is littered with fuses, primed in a pre-determined pattern.South Crofty Mine Underground 13.3 – The explosive are pushed into the drilled hole using a metal “tamping” bar.South Crofty Mine Underground 13.4 – A wide view of the drive face, it also gives a good idea of how many holes needed to be drilled for a round of blasting. The plastic tub in the foreground was the container from where the explosive was forced into the holes using compressed air.South Crofty Mine Underground 13.5 – A close up of the box of explosives. When working South Crofty was one of the biggest users of explosives in the country.South Crofty Mine Underground 13.6 – One of my favorite images on this page Vivian Mugford using a tamping bar to force the Powergel explosive into the drilled holes. In the early days of Cornish Mining this was a dangerous job and many miners suffered from horrific injuries when the charges exploded.
Nick Le Boutillier kindly wrote a few lines about blasting in South Crofty.
The most commonly used explosive was Powergel, this was a plastic explosive that came in foot-long 3/4 inch plastic-wrapped ‘sausages’. This was used at the end of drill holes to break out to the hole sockets. Also by moonlighting geologists as ‘slap dab’ to ‘blow shit up’, which was enormous fun.
South Crofty Mine Underground 13.7 – Vivian Mugford Underground Miner priming the charged holes in preparation for blasting.
The main explosive in use was anfo, which is ammonium nitrate mixed with diesel oil. This was pink and had the consistency and form of small polystyrene balls. It was blown by compressed air into the drill holes, the detonators were placed in the Powergel and the wires run out of the holes. Also these were sometimes tamped by a bit of clay to close the hole.
South Crofty Mine Underground 13.8 – Another image of the end, the many fuses can be clearly seen hanging from the drilled holes. Here Adrian is inserting the Powergel into the holes.
Trammers would sometimes use Coretex, which was a nitrate-based explosive that looked like white electrical cable. This could be wrapped around troublesome rocks and was very effective. However it was not popular, because chemicals from the explosive were readily absorbed by the skin and could easily lead to very severe blinding headaches and nausea.
South Crofty Mine Underground 13.9 – Inserting the explosives into a low hole known as a “lifter”.South Crofty Mine Underground 13.10 – The tamping bar is now deep in the holeSouth Crofty Mine Underground 13.11 – This is the final image in this set, water can be seen pouring from the roof.
On another day, the next two images are again of Adrian Mugford in another part of the mine. Once again drilling for the next blast. Present day Health and Safety laws restrict the use of these rock drills because of the extreme vibration the operative felt.
South Crofty Mine Underground 13.12 – This was possibly located in a sub level. To the right of the miner was a large hole in the ground leading to the level below.South Crofty Mine Underground 13.13 – Another closer image of Adrian Mugford drilling a face in preparation for the next blasting.
The rest of the images on this page were taken on the NPZ (North Pool Zones) crosscut on 400 Fathom Level South Crofty Mine. This was on another day with Nick Le Boutillier. This set clearly shows the ANFO explosive being blown into the drilled holes by compressed air. It was rare to hang around and have the chance to take pictures. I certainly made the most of the opportunity.
South Crofty Mine Underground 13.14 – The first image of this set show Nick Le Boutillier with his back to the camera, next to him is Miner Paul Gallie, ‘Ollie’ Warren is the miner closest to the camera.South Crofty Mine Underground 13.15 – Using compressed air the Anfo explosive held in the plastic container is forced into the drilled holes.South Crofty Mine Underground 13.16 – Adjustments being made to the Anfo injector.South Crofty Mine Underground 13.17 – The wall of the drive behind the miners is covered with primed holes.South Crofty Mine Underground 13.18 – Nick Le Boutillier Senior Mine Geologist inspects the wall of the drive. This was an important job for the geologists to monitor the ground that was being mined.South Crofty Mine Underground 13.19 – Nick would examine the line of the lode and take samples to monitor the grade of the ore.Cornish Mine Images Underground 13.20 – There was always time for a laugh and a joke. Nick and Paul sharing a few comments.Cornish Mine Images Underground 13.21 – For the miners working at the end of such a drive it was hard. The ventilation helped but was not very effective, so far underground the heat was over powering.Cornish Mine Images Underground 13.22 – The job of priming so many holes was a slow one. Also care had to be taken to make sure each charge would fire correctly.
Neil Hodges whom I met several times underground has written a piece about using explosives at South Crofty.
My first experience with explosives was at Wheal Jane back in the mid 80’s. Then, the cartridge shaped dynamite was NitroGlycerine based. If you got some on your hands and rubbed your forehead inadvertently it would give you a thumping headache! This was mainly used for rounds drilled in development ends which were often wet, because this explosive was not too badly affected by water.
Cornish Mine Images Underground 13.23 – As Nick inspects the face the two miners are clearing a small fall of rock.
At Crofty which was a much drier mine Anfo was most commonly used , this is a mixture of Ammonium Nitrate(fertiliser) and Fuel Oil(diesel). The cartridge type dynamite had changed to an emulsion paste in a plastic sausage. The trade name of this was Powergel E80.
Cornish Mine Images Underground 13.24 – As with most the sites I photographed, water was pouring from the ceiling of the drive, also it was very hot.
One cartridge of Powergel would be used as a primer if there was a chance of some damp at the back of the hole. The primer contained the detonator, so it was important that the blast was initiated well. The rest of the hole would be filled with Anfo. This was blown into the hole by compressed air. If, which was more likely the ground was dry, the detonator could be placed at the back of the hole and then loaded with only Anfo and no primer.
Cornish Mine Images Underground 13.25 – Ollie Warren moves a large rock out of the way.
Anfo’s big drawback was that water would decompose it very quickly preventing detonation. In this eventuality all the holes in the round would have to be flushed out and recharged. Worse still, a partial detonation of some of the holes could occur in the round, leaving a shattered mess at the face.
Cornish Mine Images Underground 13.26 – The lower holes are cleared of debris and the job continues.Cornish Mine Images Underground 13.27 – A low angle on the rails makes an effective angle for this image.Cornish Mine Images Underground 13.28 – Paul Gallie about to move the Anfo injector. The wall behind is covered in coiled fuse wire.Cornish Mine Images Underground 13.29 – The rails would have been laid so a Rocker Shovel could muck out the drive before drilling began.Cornish Mine Images Underground 13.30 – I was fortunate in having time to set up a slave flashgun. It has certainly added to the lighting effect.Cornish Mine Images Underground 13.31 – Ollie Warren fills up the injector with more of the Anfo explosive.Cornish Mine Images Underground 13.32 – This final image on this page is certainly one of my favorites. Mainly because the lighting and the symmetry really add to the photograph.
