Post on 09-Apr-2017
Water drainage
Darcy’s lawGroundwater flow
Design water drainage Pipelines
1
Flow through a dike
Seepage (kwel) flows through dam
Pressure line
1
Piping erosion
Water pressure
Seepage (kwel) beneath structure
civil structure
Flushing of particles
1
Dewatering (verlagen grondwaterstand)
Maximum capacitity
Well point system
Size filters
Original ground water level
1
Groundwater level
New groundwater level because of rain
percipitation Ditch or drainage
Drainage
2
Landuse / Grondgebruik Percipitation
Neerslag (mm/dag)
Groundwater level below surface
Grondwaterstandsdiepte (m)
grassland / grasland 7 (10) 0,30 (0,20)
farm land / bouwland 7 (10) 0,50 (0,30)
horticulture / vollegronds tuinbouw 7 (10) 0,50 (0,30)flower bulbs on clay soil / bloembollen op klei 7 0,50flower bulbs on sand soil / bloembollen op zand 10 0,30
fruit / fruitteelt 7 (10) 0,70 (0,60)
forest / bos 5-7 0,50 - 0,30
military training area / militair oefenterrein 7 0,70athletic fields, camping areas, play grounds /sportvelden, kampeerterreinen, speel- en ligweiden 15 0,50
building sites / bouwterreinen 10 0,50
urban area / woongebieden (50% verhard) 5 0,70
industrial area / industrieterreinen 7 0,50 2
3
Groundwater flow
Darcy’s law
3
3
Soil / grondsoort
conductivitydoorlatendheid
(m/day)heavy clay /zware klei 0.0001potklei 0.001Moderate heavy clay / matig zware klei 0.01sandy clay / zandige klei 0,05bolder clay / keileem 0,05peat / veen 0.001 - 0.1clay peat / kleiig veen 0,005sandy peat / sterk zandig veen 0,05loam /leem/löss 0,05sandy loam / zandige leem 0,3silt / lichte zavel 0,5humus / teelaarde 5shells / schelpen 30fine sand / fijn zand 1 - 10dune sand / duinzand 7coarse sand / grof zand 30very coarse sand / zeer grof zand 80
very coarse sand / uiterst grof zand 200fine gravel / fijn grind 1.000 - 10.000coarse gravel / grof grind 10.000 - 100.000
Darcy’s law
IAkq Ikv
Laminar flow
q = discharge [m3/s]k = hydraulic conductivity [m/s]A = area [m2]I = S = slope pressure line
3
]1[ Redv
w
If Rew < 5 Laminar flow
Rew = Reynolds number [1]
v = Average velocity [m/s]
d = Average grain size [m]
ν = Kinematic viscosity [m2/s] = 10 -6
3
Reynolds number
Groundwater level rise
New groundwater level because of rain
percipitation Ditch or drainage
Drainage
4
Drainage agriculture parcel
22
max/ amiddle HKaWH
4
HaHmiddle/max
W
a
K
Drainage agriculture parcel
22
max/ amiddle HKaWH
W = vertical velocity rainfall [m/s]a = horizontal distance from stream channel to highest ground water level [m]K = hydraulic conductivity [m/s]Ha = vertical distance from impereable layer to water level stream channel [m]Hmiddle= vertical distance from impereable layer to highest ground water level[m]4
Design criteria drainage pipeline• Manning’s formula• n=0,013 s/m1/3
• Sbed =1/1000• Pipe 50% filled with water• Outflow 10 cm above surface water
u = mean velocity [m/s]R = hydraulic radius [m]S = slope energy line [1] assumed is that Sf = Sbed
n = manning’s roughness coefficient [s/m1/3]nSRu
21
32
5
m 4
4/1 2 DDD
OAR
m 4)(5,0
)4/1(5,0 2 DDD
OAR
R and circle’s
5