System-built flats on a deep buried quarry

Mr. J. Peacock: 'Mr. Thorburn said that the use of the Armco liner in the piles stopped ground water from getting into the bore; but it could still fill up the bottom of the bore, as far as I could see, so really what does the Armco liner do? It seems quite expensive to put there, and I do not see how it stops water from getting into the bottom of the bore.