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You though you'd seen subsidence

Matla mines

sunny 22 °C
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Matla mines are located near Kriel east of Johannesburg and mine coal using a combination of shortwall and bord and pillar methods. Matla No. 2 has extracted from three seams, with a total extraction thickness in excess of 10m. needless to say that its shallow depth creates a signifficant subsidence impact on the surface which needs to be seen to be believed. Because the surface is grass covered it is possible to obsercethe effect of the subsidence troughs by eye. From imagery on Google maps, the location of the chain pillars pillars can be seen along with some surface ponding. Significant surface rehab also takes place. Subsidence monitoring typically takes place using photogrammetry.

Google maps link:
http://maps.google.com/maps?f=q&hl=en&geocode=&q=matla,+south+africa&sll=37.0625,-95.677068&sspn=35.494074,60.117188&ie=UTF8&ll=-26.201115,29.083643&spn=0.039276,0.058708&t=h&z=14.

Posted by Sarge78 10:17 Archived in South Africa Comments (0)

Oil from Coal

Syferfontein Colliery

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Syferfontein was originally an open cut operation named after the original farm that it occupies like many of the mine in the country. The mine operates from a couple of enteries and has mined two seams. Currently the mine extracts coal by bord and pillar method at approximately 5m high by 7.2m wide. No wonder that they make money from first workings! All of the coal is transported by overland belt to Sasol's plant where is it processed to create oil which is further refined to produce petrol. Some 40% of the country's petrol is produced by this method.

One of the production panels utilises a continous coal clearance systems from the miner using a series of loader/conveyors. Surveyors are kept busy setting sights, conducting ribline surveys and completing control surveys as the development rates are pretty good, but they're staffed well, taking up a whole office building. Most mines still use a draftsperson to prepare all their plans and Microstation is a popular package.

Posted by Sarge78 10:15 Archived in South Africa Comments (0)

Cape Town cultural heritage

a world city worth visiting

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With the weekend of, I deceide to venture down to Cape Town to see the sights. I'd been told how Cape Town can be a pretty nasty place if the weather is bad, but I must have jugged it because when I landed the rain had moved on and had been replaced by clousless blue skies and walm days. Cape Town has a rich and diverse history and visitors could spend weeks here learning all about it, but since I had two days, I chose the to biggest draw card to the cape, Table Mountain and Robbon Island.

The cable car to the table of cable mountain is quite a feat of engineering and you can't help but look up in hope that the cable doesn't break. The view for the top is breathtaking, yes the view is stunning but the air at 1100m metres is bloody cold and I could see snow about 50km away, but I was grateful that I had great visiability.

The following day I caught a boat out to Robbon Island about 8km out from Cape Town. Robbon Island also has a long and diverse history, having been used as a lepper colony, military base and most notably as a prison use to house political prisoners during the aphartide era, including Nelson Mandela for 18 years. The tour of the prison is carried out by a former prisoner and can be a moving experience as he explains some of his experiences there. Robbon Island also has a quarrying history from the time when the prisoners were made to cut limestone for the road base and other uses on the island. The whole island is now a world heritage site.

Posted by Sarge78 10:10 Archived in South Africa Comments (0)

Coal Mines are coal mines are coal mines...but not always

Douglas Colliery

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Following an early start, we head east from Pretoria to the Witbank area for my first visit to a South African coal mine. Joining me today is Dennis and Leon, Mine Surveying Inspectors from the Department of Minerals and Energy (DME). Douglas is a bord and pillar mine in the throws of winding down and will cease production toward the end of the year. The Inspectors' task today is to conduct a routine audit on selected roadway underground (typically under highways or other critical imfrastructure), ensuring that they meet design criteria and are correctly plotted on the mine plan along with a general audit of plans. One of the critical areas is the width to height ratio and the intersection dimensions. Douglas carries out first workings in multiple seams where the pillars are overlain with roadways typically in the order of 6.5m wide, Pillar factor of safety is an important consideration.

The inspection involved a conventional chainage and offset ribline survey with additional measurements taken for intersection diagonals and extraction widths. Back in the office this information is plotted along with the calculation of factor of safety and width-height ratio. Provided that these numbers are within tollerance then the inspectors are satisfied. Examination of plans typically highlights areas where the plan does not conform to the standard or reveals an omission.

Posted by Sarge78 07:20 Archived in South Africa Comments (0)

Diamonds are..

the journey continues...

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Following on from the visit to the Platinum mine, the following day I headed out to the site where the world's largest diamond was found, Cullinan. Cullinan is about an hours drive north east of Pretoria and is an otherwise quite country town, surviving on the back of the diamond mine. The mine itself is surrounded by a mining small village, hospital and fire station; it was interesting to learn that during the early 1900's miners would be required to "living-in" in an attempt to control theft. The mine is over 100 year old and has produced a significant amount of the world's diamonds including the largest which was named the "Cullinan diamond" and is now part of the British crown jewells.
Original production was from an opencut that eventually reached 400m in depth, before underground methods were used. Current depth is 800m bellow surface and uses a modified sub level caving method. The shear size and grandure of the mine is nothing like I have ever seen before, with the workshops and lunch room underground being very well apointed and even includes a fish pond.

Survey methods at the mine include real time monitoring of a nearby road using extensiometers and tilt meters, GPS monitoring of the highwall and fine dam, in addition to the typical control surveys, drivage and grade control. Due to the age of the mine some of the original plans for the area over 100 years old and impressive to see especially the draftsmanship, sadly the one thing that modern drafting lacks.

Back to survey reality here as the team consists of a 3 surveyors and 3 assistants. For a while there I thought every mine had scores of assistants.

Posted by Sarge78 09:39 Archived in South Africa Comments (0)

...Go!

The journey beings

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The long awaited visit to South Africa has begun. After months of planning I've finally landed in South Africa and have spent the last couple of days with the Mine Surveying Inspectorate, gaining an understanding of their Regulations and how they go about their surveying and drafting audits of Mines. Todays visit was to one of the Platinium mines in Rustenburg, in North West Provence.

The Platinium reef (seam) outcrops in the Rustenburg area and dips away to the North at about 15 degrees. Although some mining has occured by open cut methods, the vast majority of Mines in the area are underground. Access to the underground was very different to what I'm used to and is via a chairlift, not unlike a ski lift, down to the production level, then a 500m walk to the production unit. The Mine is very tidy and presents well but what really impressed me was the fact that they employ 8000 people at this mine, eight thousand! I was initially shocked by their safety statistics of 1 fatality, 52 Lost Time Injuries and 32 Serious Injuries, but taking into consideration the size of the workforce and excepting the fatality, thats not too bad and I'm assured that it is on the improve. The method of mining here is by longwall, but not in the same sence as a typical longwall in an Australian coal mine, but rather the face is drilled and blasted then cleared using a scraper. The supports placed are timber props and the "seam" is only 1.0m thick. Bloody hard work on your knees all day I'm sure. All ore haulage takes place using battery powered locos on rails back to the hopper and onto the belt for transport to the surface up the decline.
The survey office at the mine consists of the Mine Surveyor, Assistant Mine Surveyor, 6 surveyors, 21 assistants and one draftsperson. Wow, wouldn't that be nice back home. The methods of surveying are fairly typical and use Leica equipment for control traverses, direction and grade control. Face pickup is fairly conventional using chainage and offset from existing survey stations.

The return trip from the mine took the scenic route back to Pretoria, through an agricultural area and past the weekend retreat areas visited by these from Pretoria and Johannesburg. Roadside stalls are a frequent sight through out South Africa, with most trying to make a living from selling fruit, vegetables, exhaust systems repairs and hubcaps. Tomorrow I'm off to a diamond mine, gold will be next week. Anyone know a good jeweller?

Posted by Sarge78 10:34 Archived in South Africa Comments (0)

Ready, Set...

My first trip as part of the Surveyor General's International Fellowship is only 4 weeks away. South Africa awaits and a chance to see how they do things over there. A week with the Mine Surveying Inspectors and the opportunity to tour a few Mines might not sound like everyone's ideal business trip, but the experience will be a once in a life time opportunity. It won't be all work and no play, a trip to Kruger National Park is one of a couple of usual 'tourist' activities planned and perhaps a chance to see some local Rugby games. Then its off to the Institute of Mine Surveyors South Africa Conference before jetting back to Oz.

Posted by Sarge78 01:18 Comments (0)

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