Peele's Mining Engineers Handbook (Third edition, tenth reprint, 1963) says, of the
cross-section of shafts:
"A rectangular section divides naturally into rectangular compartments, requires least
excavation for a given hoisting area, is adapted to framed timber or steel support, and
is most widely used in metal mining for sinking in rock.
"Rounded section shafts ( circular, elliptical, oval) resist lateral pressure better, involve
less air friction per unit of area, require some form of lining other than a framed support,
and are adapted to rectangular hoisting compartments by using the surplus segmental
areas for ventilating, pipe and ladder spaces. A circular section has maximum strength
and for air shafts requires the least excavation for a given air volume. An oval or
elliptical section is stronger than a rectangular one, and shares its space economy,
but is difficult to keep plumb during sinking."
I guess the section, in each case, was decided by the engineer in charge according to
his idea of what the shaft was to be used for, the state of the ground, suspected lateral
pressure, waster-bearing strata, etc.
I am reminded of that song about a hole in the ground, when the foreman comes along
and says "You're digging it round, and it should have been square!"
Tony Brewis
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