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Mine Shafts 

 
Author: Jack Caldwell

Summary

This review describes mine shafts and shaft sinking and is a quick guide to resources on the internet about shaft sinking. It gives some general information about shaft sinking, as well as outlines regulations and guides for designing and building shafts. The review also lists shaft sinking consultants, contractors and suppliers, and gives a brief overview of closure and abandonment of mine shafts.

INTRODUCTION

To speed you on your way, here is a quick guide to resources on the internet about shaft sinking. Interspersed are my recollections of shafts I have seen and dealt with. There is a relative dearth of solid technical information on this subject via Google, so if you can add more information about your own knowledge, experience, resources, or services, please pass it along to Jack Caldwell.

Before you read my text below, take a few minutes out to see the best presentation I found while compiling this piece. It has magnificent photos and high quality cross sections mostly related to mine shafts.

RECOLLECTIONS

The first shaft I descended was that of the East Geduld Gold Mine in South Africa. I was no more than ten or twelve and what we did was probably illegal. My father was a mine captain, and for reasons I cannot recall had to go underground on Sunday morning. I must have pestered him to distraction, so along I went. Thrilling as always to the headgear that loomed so high, my courage began to flag as we stomped into the metal cage, all rusty and dripping wet. A great clang as the door was pulled closed by two large black guys who smiled a sneak smile at this terrified white boy.

All I can recall of the descent was the noise, the metal, and the water that started as a drip but which seemed to become a torrent as we went deeper, ever deeper: 6,000 feet to be precise. My father delighted in telling me "we are now at sea-level" as we climbed out the cage at the bottom of the shaft. Sea-level - flashing through my mind were those beaches of Margate where we built sand castles on our annual vacation.

There is also a faint memory of a smell. I think it is the smell of the oil skins we wore. Maybe the smell of sweat and grime. I have never smelt it again, but it lingers.

Then into a vast chamber cut in the rock. It was filled with equipment: cocopans, drills, generators, and switch-gears. The air was cold, fuelled by a vast wind blowing from fans and ducts that seemed alive. My father told me the rock was hot and we would "cook" if the fans went out. Many years later I ran the cooling plant on the Hendrik Verwoerd dam, now called the Gariep Dam, and came to appreciate the technology needed to keep big places cool.

From Graham Daws

As a post-graduate student I did some leg-work for Professor Jennings when he was asked to design the caisson needed to get through the first fifty feet of loose sands that overlay the bedrock where a new shaft was planned for a mine in Welcome. On a cold but sunny Saturday we got the pile auger to advance some shafts - about 36 inches in diameter and down through the soft sands. We set up the tripod intending to descend into the shafts to profile the soil, trying to recall the things to observe. The mnemonic was MCCSO: moisture, color, consistency, soil type, and origin. But we never did go down the holes. A quick glance was enough to establish that the groundwater was gushing into the hole and the sand, thoroughly liquefied, was storming in. As Professor Jennings remarked: "That's good information; now we know why we need a caisson."

So we designed the caisson. Somewhere I still have the notes and printout from a primitive computer code I wrote to calculate the stresses using Boussinesq's equation. (As an aside, that site has masses of equations for almost anything you can think of. Don't forget InfoMine's Find a Tool.)

Construction of the caisson began. It slid down smoothly and according to plan to a depth of about forty feet, and there it tilted and stuck. Professor Jennings, Mike Gowan, and I flew down on a second sunny Saturday. We descended to the bottom of the caisson where all was clean and fresh-smelling of new concrete. But it was obviously stuck. We walked around trying to look impressive and knowledgeable, but we were secretly baffled. In a profound and sonorous voice, the professor declared that he needed the weekend to think about it and he would phone on Monday with a plan of action.

As we exited the caisson, Professor Jennings turned to the construction foreman and in a casual, off-handed way, remarked: "Pity it can't be done, but all that is needed is a case of dynamite to go off where this thing is stuck!" We flew back to Johannesburg.

On Monday, eager to hear the professor's solution, we crammed his office. Coffee cups barely in hand, we heard his secretary announce a call from the mine. Elation and delight swept the professor's face. The news across the wires: the caisson had begun to move early Sunday morning. A case of dynamite was missing from the store and there was a bit of a mess at the bottom, but otherwise no reasonable explanation why it had begun to move again. No matter, in a few days it hit bedrock and conventional shaft-sinking began.

The lesson learnt: hire an expert to design and construct your shaft.

GENERAL INFORMATION

Infoplease has a neat piece on shaft sinking. Maybe Professor Jennings could have used this: "Shaft sinking by the freezing process in very watery soil is accomplished by sinking pipes in the area to be excavated and circulating brine at low temperature until the earth is frozen and hard so that is can be excavated in the same manner as rock."

The Classic Encyclopedia has more, and may be it source of the previous site's information-there is much similarity of text in the shorter pieces to the text in the longer piece. Wikipedia has almost nothing.

I liked the Virtual Museum Canada where there are fine photos and interesting tid-bits such as information on miner's lamps.

In the InfoMine library I found a paper on Grouting and Shaft Sinking Through Water-Bearing Ground. This is a success story worth reading. Also in the library I found a technical paper on Simulation of the Blasting Patterns in Shaft Sinking Using a Discrete Element Method. Technical stuff but thorough.

There are many great old black and white photos at Shaft Construction.

Ultimately the concrete lining of the shaft is a structure and may involve a structural engineer.


REGULATIONS

I liked this from the Mines and Quarries Act of the Government of Ireland: "Every mine shaft and staple-pit shall, save in so far as the natural conditions of the strata through which it passes render it unnecessary (either as to the whole or as to any part thereof) so to make it, be made secure, and shall be kept secure." I am not sure what this means, but it sounds important.

MSHA is more specific - see here for a comprehensive checklist of things to consider in formulating a shaft sinking plan. Another good source of items to observe is the Illinois Shaft Sinking Regulations.


DESIGN GUIDES

The first place to go to get an idea of the basics of shaft design and construction is as always McIntosh's Rules of Thumb. I liked those on timber shafts (are they still being installed?): (1) the minimum distance between the timber and the wall rock is 6 inches; (2) set spacing should not exceed 8 feet; and (3) install catch pits every six sets.

CONSULTANTS

There is of course Stantec - Mining (formerly McIntosh Engineering) to whom InfoMine is already indebted for the rules of thumb.

In the InfoMine Consultants database 14 consulting companies offer shaft sinking expertise, including Redpath Group, DMC and Dumas

I came across the German International Consulting Group for the first time - they design mine shafts worldwide.


CONTRACTORS

Layne Christensen Company could have frozen the ground at Welcome. Here is part of their project description:

"Ground freezing was used for shaft excavation support for two adjacent ventilation shafts. Each shaft measured approximately 25 feet in diameter and extended through 100 feet of water bearing sands. The freeze pipes were then drilled an additional 35 feet into the highly weathered bedrock to ensure a water-tight barrier during excavation. The groundwater table was approximately 12 feet below the existing ground surface. The contractor constructed a template of ring beams and wooden lagging to not only support the unsaturated soil, but to also establish vertical control of the excavation. The shaft was excavated using conventional air hammers, but also blasting of the frozen soil near the bedrock. Excavation proceeded ten feet into the bedrock, where the final concrete lining was constructed using bottom-up forming methods."

I cannot recall the name of the South Africa contractor sinking the Welcome shafts, but Murray & Roberts is as venerable a name in South African shaft sinking as any-take a look at their site for more-or better still call them in to sink your shaft. They have just recently announced new innovative mining technologies in shaft sinking. Also in South Africa is Shaft Sinkers; they claim 157km of vertical shaft sinking experience.

Thyssen Mining claims to be the "world leader" in shaft sinking. They must be busy. North American Drillers makes a similar claim. Frontier-Kemper Constructors, Inc. provides service to the coal mining industry. See also Harrison Western for a sober site; I like the feel and sincerity it conveys.

Shaft Drillers International lists completed projects. Confirmation of ability if you seek to employ them, and interesting reading if you are merely curious. Sad no case histories "currently available." There are three technical paper from before 2004 though.

In Canada I found Dumas who describe themselves thus: "Our highly experienced workforce is the epitome of the shaft sinking industry." Then there is Cementation who describe themselves as "one of the premier shaft sinking companies in the world."

If you need to grout to advance your shaft and to control the water that would other wise pour in, consult Eco Grouting Specialists. There is a long technical paper on Grouting of Porous Aquifers During Shaft Sinking you may want to consult first. Also see this paper on Groundwater Control in a Shaft Boring Operation.

In the UK we find Carnon Contracting.


SUPPLIERS

Shaft Sinking Equipment Manufacturing Suppliers lists them all. In the UK there is Kompass and Specialist Plant.

Deilmann-Haniel Mining Systems specialize in the construction of machinery and equipment for mining, tunneling and civil engineering applications. Their products include shaft sinking and hoisting equipment. They also make special machinery and provide individual engineering services.


CLOSURE

When the mine is done, the shaft needs to be closed and prepared for abandonment. If not..well see this California site, or this one from New Mexico.


ABANDONMENT

The following is enough to tell it all - see the site for text.


INACCESSIBLE MATERIALS

As always on the internet there is the promise of information. But so much of the promise cannot be realized unless you spend lots of money. The one paper I would love to see is titled Technology, Ethnicity and Ideology: Basotho Miners and Shaft-Sinking on the South African Gold Mines. But they give only a teaser.

If you have the money you can buy another paper I would love to read, but probably never will: Engineering Alternatives for Improved Shaft Sinking Project Payback.

From Amazon.com you could order any one of over 6,000 publications, the title of which includes "mine shaft" or one of the over 800 publications the title of which includes "shaft sinking". Or one of the over 80 publications the title of which includes "mine shaft sinking." I would like to see the 1920 book on Shafts and shaft sinking for American coal mines and the 1932 Shaft sinking practices and costs and the 1983 Kaias & Cocopans. I did read through the readily accessible 1923 Chemical Engineering and Mining Review article on shaft sinking in New South Wales, at which point I decided it was time to end this article.

But don't forget: send along your shaft sinking threads, news, views, reviews, and resources.

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