Details:

Creators:
Tyagi, Avdhesh ; Ali, Abdelfatah ; Hamilton, Matthew
Tyagi, Avdhesh ; Ali, Abdelfatah ; Hamilton, Matthew Less -
Corporate Creators:
Oklahoma State University. School of Civil & Environmental Engineering
Corporate Contributors:
United States. Federal Highway Administration
Subject/TRT Terms:
[+]
Culverts Dissipation Froude Number Hydraulic Jump Laboratory Tests Scour Streamflow
Publication/ Report Number:
FHWA-OK-14-10
Resource Type:
Tech Report
Geographical Coverage:
Oklahoma
Corporate Publisher:
Oklahoma. Dept. of Transportation. Planning and Research Division
Abstract:
This research investigates the reduction in scour downstream of a broken-back culvert by forming a hydraulic jump

inside the culvert. A broken-back culvert is used in areas of high relief and steep topography as it has one or more breaks in profile

slope. A broken-back culvert in the laboratory represents a 1 (vertical) to 2 (horizontal) slope after the upstream inlet and then

continuing 90 feet at a 1 percent slope in the flat part of the culvert to the downstream outlet. The prototypes for these experiments

were either a two barrel 10-foot by 10-foot, or a two barrel 10-foot by 20-foot reinforced concrete culvert. The drop between inlet and

outlet was selected as 30 feet. Three flow conditions were simulated, consisting of 0.8, 1.0 and 1.2 times the culvert depth. This report

represents Phase V of broken-back culverts with a drop of 30 feet. The first phase of this research was performed with a drop of 24

feet, the second phase of this research was carried with for a drop of 6 feet, the third phase of this research, performed was a drop of

18 feet, and the fourth phase of this research was performed with a drop of 12 feet.

The Froude number (Fr1) of the hydraulic jump created in the flat part of the culvert ranged between 2.53 and 5.66. This Fr1 classifies

the jump as an oscillating to steady jump. The jump began nearly at the toe by placing sills and friction blocks of different sizes in the

flat part. For new culvert construction, the best option to maximize energy dissipation under open channel flow conditions is to use one

5.83-foot sill located 33.33 feet from the outlet. The maximum length of the culvert can be reduced from 25 feet to 30 feet that was for

middle sill. For existing and new culverts, the best option is to use one end sill with height of 6.67-foot. In pressure flow conditions, the

optimal location was determined at a distance of 31.67 feet from the outlet for 4.17-foot sill. The length of the culvert can be reduced

by 25 feet to 30 feet. Also, for new and existing culverts, the optimal end sill is to use one 4.17-foot sill height under pressure flow

conditions. Such a scenario is important where right-of-way problems exist for culvert construction. Also examined was a slotted sill

which has a cut in the middle for cleanup purposes. In open channel flow conditions, the best option to maximize energy dissipation is

to use one 5.83-foot slotted sill located 33.33 feet from the outlet, and for end slotted sill is to use 7.5-foot height. In the pressure flow

conditions, the optimal slotted sill was 5-foot at a distance of 41.67 feet from the outlet, and for end slotted sill is to use 4.17-foot

height. The regular and slotted sills contain two small orifices at the bottom to allow the culvert to completely drain. The impact of

friction blocks was found to be minimal. No friction blocks were used to further dissipate the energy.


Format:
PDF
Funding:
ODOT SP&R Item Number 2254
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:2d3944ce837a877707935329b490577d2057f59882597d24d17d579fe3db5449
Download URL:
https://rosap.ntl.bts.gov/view/dot/29397/dot_29397_DS1.pdf
File Type:

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