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06 - Surface Drainage and Inlet Spacing - Pavement Surface Drainage.pdf · Inlet Spacing Formula...
Transcript of 06 - Surface Drainage and Inlet Spacing - Pavement Surface Drainage.pdf · Inlet Spacing Formula...
Pavement Drainage
Rational Method Formula
CIAQZ
Q = discharge (ft3/s or m3/s)C = runoff coefficientI = rainfall intensity (in/hr or mm/hr)A = drainage area (acres or hectares)Z = conversion factor (1 for English, 360 for metric)
2
Runoff Coefficients
Source: AASHTO Model Drainage Manual (2005)
Selected Hydrologic Soil Groupings and Slope Ranges
(for Pervious Surfaces)
Figure 6.2
3
Soil Groups
4
Runoff Coefficients
Source: AASHTO Model Drainage Manual (2005)
Figure 6.2
(for Selected Land Uses)
5
Runoff Coefficients
Source: AASHTO Model Drainage Manual (2005)
Figure 6.2
(for Impervious Surfaces)
6
Rainfall Intensity
I = rainfall intensity (in/hr or mm/hr)Pd = depth of rainfall (in or mm)Tc = time of concentration (hr)
d
c
PIT
7
Time of Concentration
Source: AASHTO Model Drainage Manual (2005) 8
Figure 6.31
2
314
9
Figure 6.3
Figure 6.4
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Figure 6.4
Suggested Return Periods
11
1
2
12
Figure 6.5
Surface Drainage
Ponding
14
Sheet Flow
15
Rolling Profile
Source: TDOT Drainage Manual (2010) 16
Pavement Cross Slope
1.5%2.0%2.5% 1.5% 2.0% 2.5%
CL
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Porous Friction Course
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Porous Friction Course
Source: http://bradeck.net/research 19
Porous Friction Course
Source: http://www.rubberpavements.org/Videos.html 20
Manning’s Equation
2132KQ S R A
n
Q = flow capacity (ft3/s or m3/s)K = conversion factor (1.4859 for English or 1 for metric)n = Manning’s roughness coefficientS = channel slope (ft/ft or m/m)R = hydraulic radius (ft or m)A = cross‐sectional area of flow (ft2 or m2)
21
Design Spread
22
Gutter Design (Uniform Slope)
Source: FHWA Drainage Manual (2010) 23
Manning’s Equation
5 813 32
xzQ S S Tn
z = conversion factor (0.56 for English or 0.377 for metric)Sx = transverse slope (ft/ft or m/m)T = spread (ft or m)
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Figure 6.6
1
2 3
25
Figure 6.6
Manning’s Equation
5 813 32
n xQ zS S T
nQQn
(depends only on geometry)
(incorporates roughness)
26
Roughness Coefficients
27
V‐Shaped Gutter Cross‐Sections
x1 x2x
x1 x2
S SSS S
Sx1 Sx2
T
29
Compound Cross‐Sections
Sw
Sx
TTsW
QwQs
Shoulder / Parking LaneGutter Driving Lane
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Compound Cross‐Sections
Sw
Sx
TTsW
QwQs
Gutter 5 813 32
s x szQ S S Tn
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Frontal Flow and Side Flow
Source: TDOT Drainage Manual (2010)
Pavement
(Qw)
(Qs)
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Gutter Efficiency
1w x
8w 3
w xo
S S1Q S SE 1Q 1T 1W
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Frontal Flow and Side Flow
s
o
QQ1 E
5 813 32
s x szQ S S Tn
(Manning’s equation for side flow alone)
(Total flow as a function of gutter efficiency)
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Gutter Efficiency
1
2
35
Figure 6.7
Figure 6.8
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Sw/Sx
1
2
3
5
4
Figure 6.8
Inlet Design
Grate Inlet
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Curb Inlet
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Inlet Spacing
Source: TDOT Drainage Manual (2010) 40
Combination Inlet
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Slotted Drain Inlet
Source: TDOT Drainage Manual (2010) 42
Inlet Spacing
Source: TDOT Drainage Manual (2010)
L L2 L2
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Inlet Spacing Formula
10,000QL0.0028Ci W
L = distance of first inlet from crest (m)Q = maximum allowable gutter flow (m3/s)C = composite runoff coefficient for drainage areai = rainfall intensity (mm/hr)
W = width of contributing drainage area (m)
44
Inlet Spacing Formula
43,560QLCi W
L = distance of first inlet from crest (ft)Q = maximum allowable gutter flow (ft3/s)C = composite runoff coefficient for drainage areai = rainfall intensity (in/hr)
W = width of contributing drainage area (ft)
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Example
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1
47
Figure 6.5
Compound Cross‐Sections
Sw
Sx
TTsW
QwQs
Shoulder / Parking LaneGutter Driving Lane
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Frontal Flow and Side Flow
s
o
QQ1 E
5 813 32
s x szQ S S Tn
(Manning’s equation for side flow alone)
(Total flow as a function of gutter efficiency)
49
Gutter Efficiency
1w x
8w 3
w xo
S S1Q S SE 1Q 1T 1W
50
Frontal Flow and Side Flow
s
o
QQ1 E
5 813 32
s x szQ S S Tn
(Manning’s equation for side flow alone)
(Total flow as a function of gutter efficiency)
51
Inlet Spacing Formula
10,000QL0.0028Ci W
L = distance of first inlet from crest (m)Q = maximum allowable gutter flow (m3/s)C = composite runoff coefficient for drainage areai = rainfall intensity (mm/hr)
W = width of contributing drainage area (m)
52
Frontal Flow and Side Flow
Source: TDOT Drainage Manual (2010)
Pavement
(Qw)
(Qs)
53
Inlet Spacing Formula
o2
10,000QEL0.0028Ci W
L2 = distance to subsequent inlets (m)Q = maximum allowable flow (m3/s)Eo = capture efficiencyC = composite runoff coefficient for drainage areai = rainfall intensity (mm/hr)
W = width of contributing drainage area (m)54