Design of Rock Chutes per Robinson

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1	language (en, es)	en
2	Design of Rock Chutes per Robinson
3	Overview:
4	Use this method to size the loose angular riprap for flow tumbling down a chute/spillway slope.
5	See Robinson 1998 Design of Rock Chutes
6	Check that the sample values correspond to the example in the reference.
7	Instructions:
8	1. Use File, Make a copy... or File, Download as... to make this file editable.
9	2. Enter slope and flow per meter (foot) in the green cells to get the riprap size you need in the yellow cell.
10	3. Note and use the important values in the yellow and red cells.
11	4. Contact Tom Haws for help or with feedback or to offer a translation.	SI		ft		in
12	Input S0, chute slope	0.06						<--- Main input
13	Input qt, total unit flow (m^3/s/m)	0.7	m^3/s/m	7.53	cfs per ft			<--- Main input
14	Input rock specific gravity	2.65						<--- Input
15	Input gradation standard deviation (D84.1/D50 = D50/D15.9)	1.25						<--- Input
16	Input np, angular riprap porosity	0.45						<--- Input
17	Is method valid for slope? 0.02 <= S0 <= 0.40?	TRUE						< --- Validity check
18	Is method vaild for rock specific gravity? 2.54 <= sg <= 2.82	TRUE						< --- Validity check
19	Is method valid for rock gradation distribution? 1.15 <= SD <= 1.47	TRUE						< --- Validity check
20	D50,1 (for S0 < 0.10) = (q*S0^1.50/9.76E-7)^(1/1.89) per Eq. 1	134	mm	0.44	ft	5.3	in
21	D50,2 (for S0 0.10 <= S0 <=0.40) = (q*S0^-0.58/8.07E-6)^(1/1.89) per Eq. 1	173	mm	0.57	ft	6.8	in
22	D50, median rock size (mm)	134	mm	0.44	ft	5.3	in	< --- Design result
23	Top crest radius = 40 * D50 per Figure 1. See also	5377.31322	mm	17.64	ft	211.7	in	< --- Design result
24	Rock extension past crest due to rounding if approach is level	161.1744699	mm	0.53	ft	6.3	in	< --- Design result
25	Thickness of rock layer = 2 * D50 per Figure 1	268.865661	mm	0.88	ft	10.6	in	< --- Design result
26	Outlet reach length = 15 * D50 per Figure 1	2016.492457	mm	6.62	ft	79.4	in	< --- Design result
27	n, Manning roughness = 0.0292 * (D50 * S0)^0.147 per Eq. 7	0.040						< --- Hydraulic result
28	Vm, velocity through rock mantle = np * (S0 * g * D/4)^0.5	0.063	m/s	0.21	ft/s			< --- Hydraulic result
29	qm, unit flow through mantle = Vm * 2 * D50 (m^3/s)	0.0170	m^3/s/m	0.18	ft^3/s			< --- Hydraulic result
30	qs, surface unit flow = qt - qm (m^3/s)	0.6830	m^3/s/m	7.35	ft^3/s			< --- Hydraulic result
31	d, flow depth above effective top of riprap = (n * qs/S0^0.5)^0.6 (m)	0.267	m	0.88	ft	10.5	in	< --- Hydraulic result
32	Notes:
33	The equations were developed using a D50 range of 15mm to 278mm rock.
34	"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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