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language (en, es)en
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Design of Rock Chutes per Robinson
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Overview:
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Use this method to size the loose angular riprap for flow tumbling down a chute/spillway slope.
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See Robinson 1998 Design of Rock Chutes
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Check that the sample values correspond to the example in the reference.
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Instructions:
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1. Use File, Make a copy... or File, Download as... to make this file editable.
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2. Enter slope and flow per meter (foot) in the green cells to get the riprap size you need in the yellow cell.
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3. Note and use the important values in the yellow and red cells.
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4. Contact Tom Haws for help or with feedback or to offer a translation.SIftin
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Input S0, chute slope0.4<--- Main input
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Input qt, total unit flow (m^3/s/m)0.05m^3/s/m0.54cfs per ft<--- Main input
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Input rock specific gravity2.65<--- Input
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Input gradation standard deviation (D84.1/D50 = D50/D15.9)1.25<--- Input
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Input np, angular riprap porosity0.45<--- Input
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Is method valid for slope? 0.02 <= S0 <= 0.40?TRUE< --- Validity check
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Is method vaild for rock specific gravity? 2.54 <= sg <= 2.82TRUE< --- Validity check
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Is method valid for rock gradation distribution? 1.15 <= SD <= 1.47TRUE< --- Validity check
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D50,1 (for S0 < 0.10) = (q*S0^1.50/9.76E-7)^(1/1.89) per Eq. 1150mm0.49ft5.9in
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D50,2 (for S0 0.10 <= S0 <=0.40) = (q*S0^-0.58/8.07E-6)^(1/1.89) per Eq. 177mm0.25ft3.0in
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D50, median rock size (mm)77mm0.25ft3.0in< --- Design result
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Top crest radius = 40 * D50 per Figure 13064.369165mm10.05ft120.6in< --- Design result
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Thickness of rock layer = 2 * D50 per Figure 1153.2184583mm0.50ft6.0in< --- Design result
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Outlet reach length = 15 * D50 per Figure 11149.138437mm3.77ft45.2in< --- Design result
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n, Manning roughness = 0.0292 * (D50 * S0)^0.147 per Eq. 70.048< --- Hydraulic result
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Vm, velocity through rock mantle = np * (S0 * g * D/4)^0.50.123m/s0.40ft/s< --- Hydraulic result
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qm, unit flow through mantle = Vm * 2 * D50 (m^3/s)0.0189m^3/s/m0.20ft^3/s< --- Hydraulic result
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qs, surface unit flow = qt - qm (m^3/s)0.0311m^3/s/m0.33ft^3/s< --- Hydraulic result
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d, flow depth above effective top of riprap = (n * qs/S0^0.5)^0.6 (m)0.027m0.09ft1.0in< --- Hydraulic result
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Notes:
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The equations were developed using a D50 range of 15mm to 278mm rock.
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"The elevation of the top of riprap in the outlet reach should be at or below the downstream channel bed elevation"
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