The manning’s coefficient for a lined trapezoidal channel with a bed slope of 1 in 4000 is 0.014 and it will be 0.028 if the channel is unlined. The area in the case of the lined section is 19.04 m^2 and for the unlined section is 29.09 m^2. What percentage of earthwork is saved in a lined section relative to an unlined section, when a hydraulically efficient section is used in both the cases?

Question

The manning’s coefficient for a lined trapezoidal channel with a bed slope of 1 in 4000 is 0.014 and it will be 0.028 if the channel is unlined. The area in the case of the lined section is 19.04 m^2 and for the unlined section is 29.09 m^2. What percentage of earthwork is saved in a lined section relative to an unlined section, when a hydraulically efficient section is used in both the cases?

asked Jul 31, 2023 in Irrigation Engineering by Carter (75.2k points)

The manning’s coefficient for a lined trapezoidal channel with a bed slope of 1 in 4000 is 0.014 and it will be 0.028 if the channel is unlined. The area in the case of the lined section is 19.04 m^2 and for the unlined section is 29.09 m^2. What percentage of earthwork is saved in a lined section relative to an unlined section, when a hydraulically efficient section is used in both the cases?

(a) 24.44 %

(b) 34.55%

(c) 50%

(d) 37.66%

This question was posed to me by my school principal while I was bunking the class.

The above asked question is from Irrigation Channels Design topic in division Sediment Transport and Irrigation Channels Design of Irrigation Engineering

1 Answer

Related questions

+1 vote

1 answer

Calculate the ratio of the tractive critical stress to the average shear stress if the water flows at a depth of 0.8 m in a wide stream having a bed slope of 1 in 3000. The median diameter of the sand bed is 2 mm.

asked Jul 31, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

A wide unlined channel carrying silt-free water has a depth of 2.0 m. The maximum slope that can be given to a channel is 1 in 10,000. Calculate the maximum tractive stress permissible on the bed to prevent scouring.

asked Jul 31, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Determine the shear stress required to move the single grain on the side slopes, if the critical shear stress required moving the similar grain on the horizontal bed is 2.91 N/m^2. Consider the angle of the side slope with the horizontal as 30° and the angle of repose of soil as 37°.

asked Jul 29, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Calculate the effective unit tractive force that causes bed load transportation if the unit tractive force produced by the flowing water is 3.20 N/m^2. The Manning’s coefficient on an unrippled bed is 0.0108 and the actual observed value of Manning’s coefficient on ripped channels is 0.0222. Take the value of critical shear stress that is required to move the grain particle as 0.5 N/m^2.

asked Sep 16, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

In a wide stream, a suspended load sample taken at a height of 0.30 m from the bed. The stream is 5.0 m deep and has a bed slope of 1/4000. The bed material can be of uniform size. Estimate the shear friction velocity.

asked Jul 31, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

What is the minimum size of the bed material that will remain at rest in a channel?

asked Jul 29, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Calculate the corresponding hydraulic mean depth that would exist in the channel if the bed was unrippled. The rugosity coefficient in an unrippled channel is 0.015 and the rugosity coefficient actually observed by experiments on the rippled bed of channel is 0.020. Consider the value of hydraulic mean depth of the channel as 1.5 m.

asked Aug 19, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Calculate the Manning’s rugosity coefficient in a coarse alluvium gravel with D-75 size of 5 cm.

asked Jul 29, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Given that the bed slope of a channel is 1 in 2000 and the discharge is 60 cumecs. The depth of the channel is fixed and is given as 2 m. The tractive force needed for the movement of bedload is? Take critical velocity ratio as 1.1.

asked Jul 31, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Calculate the critical tractive stress if the median diameter of the sand bed is 1.0 mm.

asked Jul 31, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

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.

asked Aug 15, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Calculate the central depth of a triangular channel section to carry a discharge of 15 cumecs. Consider the available slope as 1 in 9000. Assume the side slopes of the channel be 1.25:1 and manning’s constant is 0.015 for good brick work in lining.

asked Sep 16, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

The water flows at a depth of 0.6 m in a wide stream having a bed slope of 1 in 2500. The critical tractive stress is 0.53 N/m^2. Determine the motion of soil grains and the average shear stress.

asked Jul 29, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Water is flowing at a rate of 0.04 m^3/s in a soil sample of 12m thick and cross section of 50m^2. The coefficient of permeability is 1.6*10^-3m/s. What will be the seepage pressure?

asked Feb 8, 2022 in Geotechnical Engineering I by Sophia (102k points)

+1 vote

1 answer

Water is flowing at a rate of 0.04 m^3/s in a soil sample of 12m thick and cross section of 50m^2. The coefficient of permeability is 1.6*10^-3m/s. What will be the seepage force?

asked Feb 8, 2022 in Geotechnical Engineering I by Sophia (102k points)

+1 vote

1 answer

Water is flowing at a rate of 0.04 m^3/s in a soil sample of 12m thick and cross section of 50m^2. The coefficient of permeability is 1.6*10^-3m/s. What will be the seepage force per unit volume?

asked Feb 8, 2022 in Geotechnical Engineering I by Sophia (102k points)

+1 vote

1 answer

Given to design the irrigation channel to carry 80 cumecs of discharge. The channel slope is 1 in 3000. The critical velocity ratio is 1.3. Take rugosity coefficient as 0.021.

asked Jul 31, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

What will be the factor of safety with respect to cohesion of a clay slope laid at 1 in 2 to a height of 10 m, if the angle of internal friction φ=10° ; c=25 k N/m^2 and γ = 19 k N/m^3?

asked Feb 8, 2022 in Geotechnical Engineering II by Amelia (93.7k points)

+1 vote

1 answer

The shear stress required to move grain on the side slopes is less than the shear stress required to move the grain on the canal bed.

asked Jul 31, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Whose theory was the first to provide semi-theoretical analysis of the problem of incipient condition of bed motion?

asked Jul 29, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

A slope is to be constructed at an inclination of 30° with the horizontal. What will be the safe height of the slope at factor of safety of 1.5? The soil has the properties: c = 15 k N/m^2, φ=22.5° and γ = 19 k N/m^3.

asked Feb 8, 2022 in Geotechnical Engineering II by Amelia (93.7k points)

+1 vote

1 answer

Calculate the velocity over the notch (V1) and the velocity through the pipe (V3) if the full supply discharge is 2 cumecs. The area of flow over the trapezoidal notch is 0.58 m^2. Assume the value of diameter of the pipe used as 1 m.

asked Aug 15, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

For the design of non-scouring channels in coarse alluviums, the shield’s entrainment function should be ____________

asked Aug 16, 2023 in Irrigation Engineering by Carter (75.2k points)

+1 vote

1 answer

Water is flowing at a rate of 0.04 m^3/s in a soil sample of 12m thick and cross section of 50m^2. The coefficient of permeability is 1.6*10^-3m/s. The submerged unit weight γ’=9.59 kN/m^3. Calculate the effective pressure if flow is in upward direction.

asked Feb 8, 2022 in Geotechnical Engineering I by Sophia (102k points)

+1 vote

1 answer

Water is flowing at a rate of 0.04 m^3/s in a soil sample of 12m thick and cross section of 50m^2. The coefficient of permeability is 1.6*10^-3m/s. The submerged unit weight γ’=9.59 kN/m^3. Calculate the effective pressure if flow is in downward direction.

asked Feb 8, 2022 in Geotechnical Engineering I by Sophia (102k points)

Greg · Answer 1 · 2023-08-15T08:25:40+0000

Right choice is (b) 34.55%

To elaborate: The percentage of earthwork saving due to the lining is (A2 – A1)/A2 x 100.

= (29.09 – 19.04) / 29.09 x 100

= 34.55%.

Please log in or register to answer this question.

1 Answer

Please log in or register to add a comment.

Related questions

Categories