Design of lined canal
DESIGN OF LINED CANAL

Design of lined canal

DESIGN OF LINED CANAL

  • The design of line canals is always done by Kennedy’s Theory..
  • Following equations given by Kennedy are used in the design.

\[V0= 0.54mD^{0.64}\]

\[V= \frac{R^{2/3}S^{1/2}}{N}\]

Values of Rugosity Coefficients N
Values of Rugosity Coefficients N
  • The value of N for protected type of linings is taken same as for natural soil.
  • The value of N of natural soil varies from 0.02 to 0.025.
  • In order to obtain the most economical section, it is necessary to adopt the best discharging section.
  • The flow will be greater when the friction is least.
  • This happens when wetted perimeter is least for any particular given area of the channel.
Mehboob section lined canal
Mehboob section lined canal
  • In other words, the discharge will be maximum when Hydraulic mean depth (H.M.D.) is maximum.
  • A semi-circular section of channel is considered as the best theoretical section.
  • But Trapezoidal channel section is mostly adopted on practical grounds.
  • In order to increase the H.M.D., the angle subtended at the corners at bottom should be same as side slopes of channel make with the horizontal.

Design steps.

  • Following data should be known before design of the canal can be carried out:

(i) Discharge of the channel (Q).

(ii) Rugosity coefficient (N).

(iii) Longitudinal slope (S).

(iv) Slope of banks.

(v) Permissible velocity of flow

(V). Use following equations.

\[Q= AV\]

\[V= \frac{R^{2/3}S^{1/2}}{N}\]

Steps. (i)

  • Knowing the limiting values of V, N, and S find out the H.M.D.

(ii) From an expression in terms of Bed width (B) and depth (D) by pudding values in R = A /P .

(iii) From another equation in terms of B and D from equation Q = AV.

(iv) By solving equations formed in step (ii) and (iii), find out the unknown values of B and D.

  • For different values of side slopes, the sectional area, wetted perimeter, in terms of B and D is given as follows.
  • The radius of arc for monitoring bottom corners is taken equal to depth of water.
Table
Table

This Post Has One Comment

  1. alia

    great work with great content thanks for sharing

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