What are Sinkholes, they seem to be everywhere now?
It seems that every time you turn on the TV and hear the news there’s another Sinkhole appeared somewhere else be it in exotic places around the world or even locally to you. The recent problems on the Mancunian Way in Manchester, England show that these sinkholes can appear anywhere. So how and why do sinkholes form and how can we avoid seeing more and more of them in the future?
Read the following article to find out more
March saw the tragic death of Jeff Bush in Seffner, Florida, when his bedroom collapsed into a sinkhole below his house. The same month saw the disappearance – thankfully only temporary – of the golfer Mark Mihal into the ground at Waterloo, Illinois. And in August the spectacular collapse of holiday apartments at the Summer Bay Resort in Florida.
Sinkholes are natural phenomena, they occur all the time, but can be adversely influenced by human activity. Also called dolines, sinkholes are caused when soluble rocks below ground, including limestone, gypsum and salt, dissolve to form cave systems and cavities. A sinkhole is formed when these cavities collapse, or where covering materials such as sand, silt or clay funnel into the cavities, causing a collapse of the surface.
The caves may be drained and dry, but the most problematic cases are those that are water-filled and where water is also present in the soil and rocks covering them. A water-saturated mixture of sand, silt or clay can behave rather like quicksand, and becomes very mobile and capable of flowing into the the underlying cave system. It was this sort of water-saturated material that Mr Bush was unfortunate enough to fall into.
Several things can trigger sinkholes. The simple process of gradual dissolution can eventually form a sinkhole, but heavy rain or surface flooding, leaking drainage pipes, or burst irrigation mains can initiate the collapse of normally stable cavities, especially those in shallow rocks near the surface. Even the act of emptying a swimming pool has been a documented cause of a sinkhole. In Florida, soft fruit farmers counter potential frost damage to crops by irrigation from automated sprinklers fed from local wells. After several cold days, this additional draw can cause the water levels in the rock to drop considerably triggering sinkholes; one prolonged cold snap in Florida resulted in 80 sinkholes in a small area. Much of Florida has a sinkhole problem and new developments such as the Summer Bay Resort are built around small lakes or ponds present in sinkholes. As a result, it is not surprising that buildings are commonly affected.
Although sinkholes are hazardous, they can be avoided with the right kind of planning procedures, ground investigation and of course the maintenance of drains and services. Any build up of water on a weakened area can add to the risk of sinkholes appearing. They won’t ever disappear but we should be able to lower the risk of them appearing.
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