STANDARD FOR RIPRAP AND CONDUIT OUTLET PROTECTION

HOW MUCH OF A DIFFERENCE DOES THIS CHANGE MAKE ?

Lets look at an example:Q25 = 20.00 cfs, WO = 24 Inch or 2.00 ft.TW = 0.2 x DO =0.2 x 2.0 ft.= 0.40 ft., q =20.00 cfs / 2.00 ft. =

10.00 sfs

Old Equation: D50 = 0.016 x q1.33 =0.016 x 10.001.33 = 0.855 ft.

TW 0.40 ft.New Equation: D50 = 0.020 x q1.33 =0.020 x 10.001.33 = 1.069 ft.

TW 0.40 ft.

1.069 ft. = 1.25 = 25% Increase in D50

0.855 ft.

PREFORMED SCOUR HOLE SECTION HAS BEEN REARRANGED TO “FLOW” MORE LOGICALLY

HORIZONTAL APRON SECTION HAS BEEN REARRANGED TO “FLOW” MORE LOGICALLY

DO0.5

ISHBASH CURVE – CHANNEL RIPRAP

ISHBASH EQUATION

Vc is not the velocity correlated with Minimum Specific Energy !

FIGURE TS14C–6 GRAPHICAL SOLUTION FOR ISBASH TECHNIQUE FOR DIFFERENT STONE

DENSITY

DIFFERENT STONE DENSITY

AVAILABLE FOR VERY HIGH VELOCITY CIRCUMSTANCES

LANE METHOD – CHANNEL RIPRAP

RIPRAP QUESTIONS ?