What is the range of value of Manning's coefficient for straight alignment for cast in-situ concrete lining?

0.020 – 0.025

0.018 – 0.020

0.015 – 0.018

0.012 – 0.015

Correct Answer : 0.015 – 0.018

Explanation : In absolutely straight reaches and with relatively higher discharges lower values of Manning’s constant may be attained. For cast in-situ concrete lining, the value of n varies from 0.015–0.018 and for cement plastered masonry the value varies from 0.012-0.015.

Recently Updated in Irrigation Questions

Which type of lining is mixed and placed under temperature?

Dry Stone Lining

Shotcrete Lining

Cement Concrete Lining

Asphaltic Concrete Lining

Correct Answer : Option (D) : Asphaltic Concrete Lining

Explanation : Asphaltic concrete lining has been under evolution. It is used in very few places. This concrete is a careful mixture of asphalt and graded stone aggregate, and is mixed and applied under elevated temperature. This is a flexible lining and readily confirms to subgrade.

Calculate hydraulic mean depth for concrete-lined channel to carry a discharge of 350 cumecs at a slope of 1 in 5000. The value of manning’s constant for the lining is 0.015. The side slopes of a channel may be taken as 1.5:1. Assume limiting velocity in the channel as 2m/sec.

2.20 m

2.40 m

2.60 m

2.80 m

Correct Answer : Option (D) : 2.80 m

Explaination : Using Manning’s equation: V = 1/n.R2/3.S½
2 = 1/0.015 x R⅔ x 1/5000½
R = 2.80 m.

What is the maximum permissible velocity in Cement concrete lining (Unreinforced) as per Indian Standards?

1.2 to 1.8 m/sec

2 to 2.5 m/sec

1.5 to 2 m/sec

1.5 to 2.5 m/sec

Correct Answer : Option (B) : 2 to 2.5 m/sec

Explanation : The maximum permissible velocity for unreinforced cement concrete lining is 2.0 to 2.5 m/sec. For Boulder lining, the maximum permissible velocity is 1.5 m/sec.