Develop a conceptual design for a trapezoidal concrete Gunit

Develop a conceptual design for a trapezoidal concrete (Gunite) channel that is sized to convey a design discharge of 50 m3/sec. Evaluate the feasibility of constructing a channel with a bed slope of 0.005, a bed width of 3 m, and side slopes of 2:1 (horizontal:vertical). Determine the design flow depth. If the flow depth exceeds 1.5 m, the design will not be feasible. Comment on the feasibility of the design and, if necessary, discuss ways the channel might be modified to comply with the maximum flow depth of 1.5 m.

Solution

Solution:-

Given

Q = 50 m³/s

B = 3 m

S = 0.005

Let C =45

Side slope = 2:1

So m =2

Let flow depth = y

We know that

Q = AV

Q = (B + my)y * C (R*S)

Q = (B + my )y * C (y/2 *S)

50 = ( 3 + 2y)y * 45 * (y/2 * 0.005)

Flow depth y = 2.11 meter     Answer

Flow depth should not be greater than 1.5 m . For decreasing flow depth we will have to increase size of bed width.