Movement of Sand in Tunnels

The movement of sand and finely crushed rock in tunnels is investigated. A basic assumption is that the amount of transported material per unit time is low. Two problems have been distinguished and dealt with: (1) The general aspect of sand movement in a horizontal tunnel and; (2) the conditions for uniform sand movement in tunnels with variable slope. An analysis, based on present information of erosion in open channels, leads to equations for (1) calculating limiting size of particles being moved; and (2) the variation of cross section necessary to maintain uniform sand transport in long tunnels with variable slope. Coefficients are determined on the basis of laboratory tests and field data.