Page 559 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch14_500-554.qxd 8/7/10 8:56 PM Page 517

14.7 Common Elements of Sewer Profiles 517

M.H. M.H. M.H.
C g 0.033% C C
EI. 19.1 19.0 EI. 19.1 g 1.00% M.H.
Excess depth h 1 = 0.9´ Entrant depth minimum s Excess depth h 2 1.8´ Depth 7.9´ Excess depth h 1 = 0.9´ Sewer, laid at s
minimum
Case a
Case d
Depth 7.9´ g minimum s g
minimum s C 16.1
Entrant depth
minimum
Sewer, laid at minimum s
g
Depth increases
to minimum
V = 2.5 ft/s Depth 8.8´ Depth decreases Depth 7´
EI. 11.20 EI. 11.20
10˝ V 3.64 ft/s
EI. 10.37 s 0.33% 10.20 EI. 10.37 10˝
9.37 s 0.70% 9.10
M.H. 8.27
M.H. C
C M.H. EI. 19.1 g 0.70% M.H.
EI. 19.1 g 0.33% C
18.1 Case e C 17.0

Case b
Depth 7´ Sewer, laid at minimum s Depth 7´ Depth 8.9´ Excess depth h 1 = 1.9´ Sewer, laid at s minimum Depth 7.8´ Excess depth h 2 = 0.8´
g
minimum s
g minimum s
Entrant depth
minimum
g
Depth is uniform
V 2.5 ft/s Depth decreases
EI. 12.10
EI. 11.27 10˝ s 0.33% 11.10 EI. 10.20 V 2.5 ft/s
10.27 EI. 9.37 10˝ s 0.33% 9.20
8.37
M.H. M.H.
C C
EI. 19.1 g 1.10% EI. 19.1
M.H. g 1.00% M.H.
Case f
C g
minimum s C 16.1
Depth 7´ g
minimum s 15.8 Depth 7.9´ Excess depth h 1 = 0.9´ Entrant depth
minimum
Case c
g
Entrant depth minimum
Sewer, laid at s g Sewer, laid at s minimum
Depth is uniform Depth 7´ by use of drop manhole
EI. 12.10 Velocity decreases but Depth 7´
depth is increased
EI. 11.43 8˝ V 3.93 ft/s
EI. 11.20
EI. 10.37
EI. 10.10 V 2.5 ft/s
s 1.10%
8.80 EI. 9.27 10˝ s 0.33% 9.10
8.13 8.27
Figure 14.15 Common Elements of Sewer Design.
3
3
Required: q 1.2 ft /s 33.98 L/s; Q 1.2 ft /s 33.98 L/s; V 2.5 ft/s 0.76 m/s;
N 0.012; L 300 ft 91.44 m.
Minimum depth to crown 7.0 ft 2.13 m.
3
8-in. (200-mm) sewer: Q 1.2 ft /s 33.98 L/s; S 0.84%; V 3.4 ft/s 1.04 m/s.
3
10-in. (250-mm) sewer: Q 1.36 ft /s 38.52 L/s; S 0.33%; V 2.5 ft/s 0.76 m/s.
Conversion factors: 1 1 in. 25.4 mm; 1 ft/s 0.3048 m/s; 1 1 ft 0.3048 m.