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Sachpazis: Design of a surface water drain

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Hydraulic Design of a Surface Water Drain

Hydraulic Design of a Surface Water Drain

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• 1. Project: Design GEODOMISI Ltd. - Dr. Costas Sachpazis Job Ref. of a Surface Water Drain Section Sheet no./rev. 1 Civil & Geotechnical Engineering Civil & Geotechnical Engineering Consulting Company for Calc. by Structural Engineering, Soil Mechanics, Rock Mechanics, Foundation Engineering & Retaining Structures. Date Chk'd by Dr.C.Sachpazis 10/11/2013 - Date App'd by Date DESIGN OF A SURFACE WATER DRAIN L h Drain design details 3 Design flow rate; Qdesign = 5.00 m /s Length of the drain; L = 250.0 m Fall along length of drain; h = 25.0 m Gradient of drain; i = h / L = 0.100; (1 in 10) Minimum flow velocity; Vmin = 0.750 m/s Minimum pipe diameter; Dmin = 200 mm Surface roughness; ks = 0.6 mm Mean hydraulic depth factor; m = 0.25 Kinematic viscosity of fluid; ν = 1.31×10-6 m2/s × Using the Chezy equation Constant; c = 56 Diameter of pipe required; D = ((Qdesign × 16) / (π × m × c × i × 1m/s )) Nearest pipe diameter; Dchezy = 900 mm Flow velocity using Chezy; Vchezy = c × √(m × Dchezy × i × 1m/s ) = 8.400 m/s 2 2 2 2 2 0.2 = 876 mm
• 2. Project: Design GEODOMISI Ltd. - Dr. Costas Sachpazis Job Ref. of a Surface Water Drain Section Sheet no./rev. 1 Civil & Geotechnical Engineering Civil & Geotechnical Engineering Consulting Company for Calc. by Structural Engineering, Soil Mechanics, Rock Mechanics, Foundation Engineering & Retaining Structures. Date Chk'd by Dr.C.Sachpazis 10/11/2013 - Date App'd by Date Using the Escritt equation Diameter of pipe required; 3 D = (Qdesign × 1000 × √(1 / i) / 0.00035 m /s) 0.382 × 1mm = 840 mm Nearest pipe diameter; Descritt = 900 mm Flow velocity using Escritt; Vescritt = 26.738 × (Descritt / 1mm) 0.62 ×1 m/s / (√(1 / i) × 60) = 9.563 m/s Using the Colebrook-White Equation for pipe running full and partially full Design pipe diameter; Ddesign = max(Dchezy, Descritt, Dmin) = 900 mm Constant; Z = √(2 × (gacc / 1m/s ) × (Ddesign /1000mm) × i) = 1.329 Flow velocity; Vfull = - 2 2×Z×log((ks/(3.7× Ddesign))+((2.51×ν)/(Ddesign×Z×1m/s)))×1m/s Vfull = 9.932 m/s Flow rate running full; 2 3 Qfull = Vfull × π × Ddesign / 4 = 6.32 m /s PASS - Maximum flow rate is greater than design flow rate From Hydraulics Research Tables 35 and 36 Depth as proportion of D; x = 0.673 Flow velocity at design flow rate; Vdesign = 10.986 m/s PASS - Design velocity is greater than 0.750 m/s