Would you prefer a house constructed on ground that’s subsiding or one on ground where sinkholes pop at the surface? A “mining house” (Ref. 1) or a “sinkhole house” (Refs 2, 3). And if you had the one or the other, what could be done about it?
I thought this on reading the item in The Chronicle Herald on February 14, 2020 about Pictou County’s “mining houses”. How an area’s coal mining history can sometimes come to the surface in unwanted ways and how these zones are not always known to home owners and buyers. (Ref. 1)
I would pick a “mining house” on ground underlain by deep mines rather than a “sinkhole house” underlain by Karst terrain – ground prone to sinkhole formation. That’s because geo-engineers can analyse subsiding ground with some certainty and predict where it will occur and the amount. It’s not so easy and cost effective to analyse and predict where sinkholes will occur. (Refs 2, 3)
(Geo-engineers – short for geotechnical engineers, a specialty of civil engineering)
Geo-engineers have lots of existing evidence on subsiding ground that they can analyse. Evidence like the following:
- The location and depth of the underground mine,
- When it was worked,
- The type of ground overlying the mine,
- The contour of the ground now,
- The condition of the houses and,
- Published data on problems like this elsewhere in the world – like in the UK.
This is the evidence that I would gather together and analyse, and tell you a lot after I was done.
There’s also lots of information on this type of problem in the UK where I practiced for three years.
How does a “mining house” problem relate to forensic engineering?
It’s because the problem isn’t too much different from other problems in engineering, including forensic engineering. You can learn a lot from existing evidence, sometimes very little existing evidence.
I was told about cracks in a building wall one time and the material used to construct the wall – the building was not in mining or sinkhole country. The cracks had been caulked suggesting they were large enough. I was not told about the shape of the cracks nor did I see the wall. But, based on their size and a few years forensic and geo-engineering experience I knew the likely shape of the cracks and the cause.
It’s the same in mining country. An experienced geo-engineer would examine the condition of the houses on the subsiding ground and beyond, input this to the other evidence and tell you a lot about the situation in the area. Including where not to build or buy. That’s possible in Pictou County.
- The Chronicle Herald, page A8, Halifax, February 14, 2020
- Update: Sinkhole news highlights a problem that can be fixed. Posted April 8, 2019
- Sinkholes: A litigious matter? Posted September 15, 2017