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I made this speech at the Geotechnical/Geomechanical Australian Conference in 1993 and it can also be found in my book Never a Dull Moment. If you like this yarn you can download the book as a PDF. The book is full of it (exactly what some people have said about me).

Geotechnics and the Goldfields

Tad Szwedzicki asked me to say a few words about geotechnics and geomechanics in relation to the local goldfields. It’s a pretty safe subject considering my remarkable ignorance of such technical topics. I understand however, that geotechnics is the application of technology to geomechanics in an endeavor to prevent unexpected movements of earth and rock in relation to mining. It also has the side benefits of increasing productivity and saving lives.

Now having covered the subjects of geotechnics and geomechanics I would like to go my own way with some comments about growing up on the Goldfields. I’ll explain how that equips one for dealing with similar unexpected events, then in some way link it with it my only firsthand experience at ground failure on the Golden Mile. That assisted one of Western Australia’s most remarkable, but understated success stories, Stan Perron.

Let’s go right back into the dim dark past…

Incident no.1

At the age of six I was living with my parents in Croesus Street, Kalgoorlie. Back in those days we had to make our own fun. As you may have heard, there was no TV. Croesus Street was very quiet and few people actually knew where it was (at the Mt Charlotte end of Kalgoorlie). There were only eight houses in the street and on one side was the old Victoria Park. It was a rather delightful park at the time. In the park’s corner, where the current playground of the Infant Health Centre is, there was a large goldfish pond full of goldfish. The pond, incidentally, was the original Kalgoorlie public swimming pool but I can’t remember back that far.

Early on Sunday mornings, I was joined by a couple of similarly-aged companions. We used to go fishing with cotton reels, bent pins and soft bread as bait, and always managed to haul in some goldfish. We didn’t take them home for eating, we just threw them back — we were in it for the sport. One morning we arrived to find a pyjama-clad man floating face down, right in the middle of the goldfish pond. With our lines out we hooked on to his pyjamas and pulled him over to the edge. I guess we built up a bit of speed and by the time his head hit the concrete side he was moving fast. I have always worried about this but I presume he was dead before he hit the pond wall.

Only being in it for the sport, we of course threw him back. Now, at age six it didn’t really mean much to me. But when I mentioned our adventure over the breakfast table, I was impressed at the speed with which my father made several phone calls and disappeared for an hour while the matter was sorted out.

Incident no.2

There was another incident, over in the same park, some two years later when I heard some blasting. Asking my mother what it was, she said that they were probably blasting tree stumps over in the park. That sounded like something that I should get involved in, so I dashed over just in time to see a pair of hips with crossed legs, sitting in the rotunda.

Just this pair of hips sitting on the bench and the rest of him was all over the ceiling of the rotunda. Someone else walked up and told me that he had observed what had happened. He saw this fellow sitting reading the newspaper and thought that he was smoking. The smoke must have come from a lighted fuse as obviously he had a stick of gelignite in his mouth. I can remember quite vividly helping the undertaker scrape all the pieces off and load them into a chaff bag. I can remember also the look on my mother’s face when I got home with blood right up to my elbows. She was somewhat horrified and gave me a good scrub up.

I didn’t tell her about the collection of vertebrae that I had in my pocket. Needless to say, I was a ten-minute hero at school the next day, with my adventure story and my grisly evidence.

Incident no.3

That leads me to a third event that occurred about eight years after that, when I was 15-and-a-half-years-old. A friend and I would take our old unlicensed motor cycles out into the bush after High School and practice, while we counted the days to getting our driver’s licence. This particular day we saw dust rising, not far ahead, through the scrub, and when we investigated we came upon a scene that remains one of my permanent memories.

Airlines (WA) Ltd, later McRobertson Miller Airlines (or MMA as we called it), was the fore-runner of Ansett with daily flights from Perth using De Havilland Dove planes. Their capacity was nine passengers, a pilot and an air hostess. That day, on its approach to Kalgoorlie, the plane had snapped a wing off and fallen like a stone from the sky. Unlike in the movies there were no flames, no smoke, just stark evidence of the explosive effect of impact on the plane, the passengers and their possessions.

We immediately claimed our finder’s privileges. My prize was the set of fabric backed pilot flight maps which looked as though they had been compressed diagonally in a hydraulic press. I also retrieved one half of the pilot’s headphones, the other half was in a thousand pieces; and of course, there was the inevitable collection of vertebrae.

Unexpected events will give you plenty to do

Now, when I hear people say that there is nothing for young people to do on the Goldfields, I think back at my frantically busy youth where there always seemed to be plenty to do and I feel sure that these wonderful opportunities still exist for today’s young people. All that proves is that life is full of unexpected events and that is exactly what geotechnics is supposed to deal with.

Now let us skip another six years to bring us to 1958, when I had my first direct contact with mining geomechanics, again with an unexpected event, this time involving the Golden Mile. It created a business opportunity for our family company, WG Manners & Co, but it also created a much more significant business opportunity for another person. The event was a spectacular subsidence on the Perseverance Lease, within a few meters of the main Gold Mines of Kalgoorlie administrative office and the Boulder Block Hotel, which many of you will remember.

At 2am on April 27, 1958, the tree covered area simply subsided, leaving a large surface cavity. This gaping void took some of the floor of the winder house, almost to the chair of the winder driver. This vast hole was quickly filled with 70,000 cubic yards (yes, the old imperial measurement) of residues from the South Kalgurli Dump. This 70,000 cubic yards was placed quickly by the first Euclid Twin Power Scraper that we had ever seen in the State and I’ll comment later on the significance of that point. As this tailings residue was being placed, salt water sprays were used to wet and consolidate the fill. Later, pipe spears were driven into the fill near the winder and more salt water used.

The mine management decided to replace the winder in its original position, so it was necessary to stabilize the area to reduce further incidents like this. Movement had occurred in the top 500 feet of the main shaft and was obvious when looking at the alignment of the shaft timbers.

(In)dispensable Pete

After the heavies from the mine’s Kalgoorlie office, their head office and the Mines Department had been and gone, they looked for somebody “dispensable” to inspect the many cavities underground, to report on the present situation and recommend action to stabilise the area around the shaft. One of their bright young mining engineers of that time, Peter Dunn, the “Assistant to the Underground Manager, Eastern Leases”, seemed ideal because of his youth and agility and they decided to throw him this challenge, with a view to early advancement if he managed well. He must have, as within a relatively short time he was elevated to “Section Underground Manager”.

Peter later went on to become the chief mining engineer for Westpac Bank, and more recently the Chairman of Beach Petroleum and its parent company, Claremont Petroleum and he was featured on the front page of last week’s Financial Review detailing their successful $44 million damages claim against the Independent Resources Group and former directors.

Peter has helped me by providing his file notes from the 1958 subsidence.

The mine management allocated Bill Woosnam to accompany Peter Dunn on his underground inspections, to crawl around under broken timber and fallen rock, and to look into old workings. Peter commented that his sometimes rash enthusiasm was balanced by Bill’s extensive experience in Welsh coalmining and many years underground on the Golden Mile.

The two of them saw places that hadn’t been visited for decades. They confirmed the cause of the subsidence to be a two-foot slippage of a block estimated at 300,000 tons (imperial), this being caused by the previous management allowing mining of the Lake View Lode, and “F” lode adjoining it, on the east, between the five and nine levels, without sufficiently substantial pillars.

If you can imagine two thick saucers standing vertically rim to rim — there are the ore bodies. The zone between is barren rock, shaped like a discus. The “saucers” were mined leaving inadequate support so that the “discus” of 300,000 tons slumped vertically two feet. The Lake View Lode stopes, from surface alongside the winder, to the five level (523ft) were filled, as was the “F” Lode “saucer”. The opposite “saucer”…Lake View Lode…was empty prior to April 27, the day of the subsidence.

When the “discus” block slumped, crushing the slender pillars previously holding it in place, an opening was created, allowing the old sand fill to run into the empty Lake View Lode below the five level. A vertical pillar then fell into East Lode allowing sand to pass into an empty stope. These movements of sand drew material right through from the surface under the winder room.

Peter’s task was to recommend procedures to stabilize the area around the main shaft. This meant filling all stopes and cavities by the best means possible. Unknown to him, the WMC board had assumed that hydraulic fill was the obvious way to go. Luckily the culture of the company at that time was: “the best idea wins regardless of who proposes it”. With so many inaccessible drives, cracks and faults, it would not have been possible to contain or control hydraulic fill.

Dry “fill” from the Trafalgar residue dump was used, mainly tipped down existing winzes and shafts and through open stopes. Underground, it was conveyed to the place to be filled, and this is the part that WG Manners & Co enjoyed.

 

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