rock chute mike cox state conservation engineer contractor certification training march 2008
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Rock Chute
Mike CoxState Conservation Engineer
Contractor Certification
Training
March 2008
Purpose: Stabilize the grade and control erosion in channels. Prevent the formation or advance of gullies.
Grade Stabilization Structure (410)
Rock Chutes are commonly used to
control grade in Indiana
Rock Chute-Advantages
• Most of the construction can be done with a backhoe or excavator
• Economical compared with poured concrete
Rock Chute - Disadvantages
• Rock can move during large storms• Hard to find larger rock sizes in certain areas• High overfalls require long chutes • Small rock size increases width and length of
chute
Rock Size vs Velocity
What is a d50?
• Expressed as D50 size (50% maximum passing by weight)
RIPRAP GRADATION
d50 = 7 INCHES
SIZE % PASSING
14 100%
7 50%
2.3333 15%
Example:p1 = 24”
p2 = 19.2”
D50 = (24” + 19.2”)/8
= 5.4 inches
Bedding
• Minimum Thickness = 6”• INDOT Sizes Specified
Geotextile
Riprap Thickness
• Minimum of 1’ thickness• Must be 2 times D50 size
Example:
If using D50 Size = 7” Riprap
Minimum Riprap Thickness = 2 * 7” = 14”
2xD50 min.
Installation Report
http://www.in.nrcs.usda.gov/technical/engineering/engineering.html
Landowner:Rock Chute Number or Location:TBM # and description:TBM Elev: TBM reading: HI:
I certify that I have constructed the Rock Chute in accordance with this report and the NRCS plans and specifications.Contractor: Signature: Date:
(print name)
ROCK CHUTE CONSTRUCTION CHECKOUT SHEET
Rock size:
SURVEY
Construction Tolerances-Rock Chute
Depth at Centerline: Grade to 0.1 foot below
Width: 10% wider not to exceed 1.0 foot
Top of Levee: Grade or above
Side Slopes: +0.1 ft./ft.
Helping People Help the Land
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