Economical Canal Cross Sections

The use of machines for trimming the subgrade and for placing concrete lining in canals has dispensed with the need for simple cross sections composed of straight-line segments. By the use of curved canal cross sections, the hydraulic properties are improved, resulting in a substantial saving in concrete and excavation. This paper shows the method of analyzing several typical curved sections, as well as the most economical trapezoidal section for comparable paving-machine speeds. As the paving machines have cover forms for the concrete which move continuously, their speeds will depend upon the properties of the concrete and upon the steepness of the cross section. An index of steepness is derived in the paper and, assuming the mix to be constant, the speed of the machines is assumed to be constant for cross sections having the same steepness index. This provides a basis for comparing various sections all having the same steepness index.