GATE 2025 Civil Engineering PYQ

Question

Lacey's regime equations, followed in India for making scour calculations while designing hydraulic structures across alluvial channels, are given below. Regarding these equations, which of the following statements is/are true:

$$ \begin{aligned} & D=0.470 imes\left[\frac{Q}{f_s} ight]^{1 / 3} \ & P=4.75 imes \sqrt{Q} \ & f_s=1.76 imes \sqrt{d} \end{aligned} $$

where, $Q$ is discharge and $f_s$ is silt factor

Accepted Answer

$P$ is the Lacey's waterway width

Answer

$D$ is the depth of scour below the existing riverbed

Answer

$d$ is the average grain size diameter of the bed material in centimetres

Answer

$D$ is the depth of scour below the design flood level