Last week I left you to consider the need for water pumps in a mine.
If you thought about this picture, where the mine entrance used to be just off the sea shore, you can probably imagine that flooding would be a constant battle, but a mine doesn’t have to be next to the sea to have to deal with underground water.
There’s plenty of water in the ground. When it rains some soaks into the soil and it keeps trickling down into the rock, provided there is a way through. Many rocks have cracks or tiny pores spaces within them. Water will flow down until it can’t go any further. Either there are no more holes, or the further holes are already full of water. If there is no way out, then any spaces through the rock gradually fill with water.
So, if you want to dig a mine shaft, in order to dig out a coal layer from deep in the ground, you are likely to come across water. And as soon as you dig a hole, well that’s an easy place for water to collect…
So, mines usually need to operate pumps, to extract the water and stop the shaft and underground passageways from becoming flooded.
When the mining is finished and the pumps are shut off, won’t everything just go back to how it was before? Well it can’t, because under the ground things are not as they were before. We’ll look in more detail next week.