12/9/2013

1

Water structures on watercourses

loads on water management structures

weirs and waterways

Assoc. Prof. Petr Valenta

Department of hydraulic structures

Stability of hydraulic structures

Loads on hydraulic structures

Hydraulic structures require careful assessment of loads and stability analysis – safety of the

structure is the main criterion

Permanent load

Imposed load

water pressure, earth pressure, dead (self) load

long term (movable equipment, water pressure,

earth pressure, thermal loads, creep, shrinking,

support settlement)

short term (ice, wind and snow loads, impacts

from vessels, loads during construction,

mounting)

extreme (extreme water pressure, seismic loads,

subsoil strain - undermining)

Charateristic (specified) loads – serviceability limit state criterion (deformation)

Design (factored) loads – ultimate limit state criterion (characteristic x load factor f)

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Most common loads

Self weight of the construction

volume x material unit weight, according to standards or laboratory tests

f < 1 – positive effects (stability assesment – 0,9)

f > 1 – negative effects (assesment of bearing capacity – 1,1)

concrete 23 – 25 kNm-3

Hydrostatic water pressure

2

2

1hPhp ww

p – hydrostatic pressure

pressure diagram – vertical wall

hw.

h

3

h

P

Hydrostatic water pressure pressure diagrams

navigation lock gate (Labe, Hořín)

head water

tail water

head water

tail water

1P

2P

P

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Hydrostatic water pressure

2

112

1hPhp ww

p – hydrostatic pressure

pressure diagrams – inclined straight wall

direct method horizontal and vertical components

1P

2P 1h

2h

h1.hw

hw.

1h

2h

h

hw.

hP

vPfictive vertical wall

Hydrostatic water pressure on a curved surface

hp wp – the hydrostatic pressure

direct method - complicated 1/ horizontal component of force

F passes through the center of

curvature (pressure perpendicular)

Projection of the curved surface

onto a vertical plane

C – centre of curvature

vP

hP

P

hhw

hP

fictive vertical wall

h

hw

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Hydrostatic water pressure on a curved surface

3/ composition of forces 2/ vertical component of force

calculated as weight of the water body

above the surface

vector sum – the resultant force P also

passes through center of curvature

wv AP .

hP

hP

vP

P

Hydrostatic water pressure on a curved surface

1/ project the curved face onto a vertical plane,

calculate horizontal component

2/ calculate the vertical component from the weight

of the water above the surface (displaced water)

3/ calculate the magnitude and direction of the

resultant force

application – hydrostatic force on the face of radial gate

wall head water

bottom

h

1hC

1h

vP

hPP

1.hw

hw.

fictive vertical wall

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Most common loads

Earth pressures

pressure at-rest, active and passive pressures

deformation – tilting of retaining wall example

pressure at-rest

active pressure

passive pressure

Lateral earth pressure

azaaza KhEhKp 2

2

1pzppzp KhEhKp 2

2

1

24

2tgKa24

2tgK psin10K

Influence of cohesion

ppzpaaza KchKprespKchKp 22 .

h

h

pp pa

Ep

Ea

Active

Passive

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Earth pressure

Earth pressure of saturated soil – combination of hydrostatic water pressure with earth pressure

Lateral pressure of silt – approximation by heavy liquid

earth

pressure

water

pressure

groundwater table

dry soil

unit weight

saturated soil

submarged unit

weight

silt

water

Hydrodynamic water pressure

hydrostatic x hydrodynamic pressure

w = 10 kNm-3 f = 1,0 (1,1 – 1,2 dynam.)

for periodic effects simplified approach – dynamic factor = 1,3 – 2

experimental laboratory research (intermediate gate positions)

diagrams of hydrodynamic pressure

tail water

flap gate

surface

(tilted gate)

flap gate surface (intermediate position)

0,5

H

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Wave pressures

L – length of the reservoir or weir pool (in km)

V – wind velocity (based on meteorological data, or ~ 120 km/h)

7602700320 4 ,,, LVLhw

Possible types of waves

wind (see above), from moving vessels, translational discharge waves, shock waves

In addition to the static water loads the upper portions of water structures are subject to

the impact of waves.

Waves are generated on the surface of the reservoir by the blowing winds, which exert a

pressure on the structure.

Wave pressure depends upon wave height which is given by the empirical equation

Wave pressure

wh3

4

wh3

2

wh3

1

wh8

1wh

8

3

wP

wave crest

wave crest (obstructed) dam

still water level

www hp 42.wwwwww hhhP 2

3

542

2

1).(

7602700320 4 ,,, LVLhw

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Ice pressure

temperature changes additional ice weight additional weight of ice cover

(drop of water elevation) (prevention of movement)

The ice which may be formed on the water surface may melt and expand.

F is function of ice thickness, scale, rate of temperature rise resulting in expansion, physical

properties of ice in the plastic - elastic state and the degree of restraint existing at the perimeter of

the ice sheet.

lack of physical data – estimated values ~ 200 – 500 KNm-2

protection against the effects of ice forces – for example heating of constructions, bubbling

dynamic effects of ice – impact (strokes) of floes – piers, stilling basin slab

h

L

Seepage and uplift pressures

Possible problems of seepage

A/ The percolating water exerts an upward pressure on the foundation of the weir or barrage.

Uplift reduces the effective weight of the structure and consequently the stability is reduced.

B/ The force of percolating water can remove fine soil particles – possible failure by piping or

undermining

tail water

head water

total head

hydraulic head H

losses

Seepage flow characteristics

1/ hydraulic head H (uplift pressure assessment)

2/ hydraulic gradient i = dH/dL (internal erosion - piping assessment)

3/ seepage velocity v = i . k (Darcy’s law) k = hydraulic conductivity

pathline of the length L

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Uplift pressures

exact method – numerical models based mostly on the finite element method

approximate method – Bligh’s, Lane’s creep theory

Assumptions :

1/ the percolating water follows the outline of the base of the hydraulic structure

2/ the loss of the hydraulic head is proportional to the length of the creep

(linear course of the hydraulic loss, constant gradient of hydraulic head)

hv LLL

sheet-pile wall

creep length L

Safety against piping

hv LLL3

1anisotropy (horizontal seepage easier) Lane

Bligh hv LLL

i = H/L = 1/C L > C.H

According to Bligh and Lane, the safety against piping can be ensured by providing sufficient creep

length, given by L = C.H, where C is the Bligh’s (Lane’s) coefficient for the soil.

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Safety against uplift pressure – construction of the uplift pressure diagram

sheet-pile wall

upstream blanket

tail water = datum plane

datum plane

hyd

rau

lic h

ea

d

acco

rdin

g to

th

e B

ligh

’s

assu

mp

tion

s

hyd

rosta

tic

pre

ssu

re u

nd

er

the

tail

wa

ter

Stability assessment - sliding stability

•on excavation line (foundation joint)

•on construction joints

•on subsoil surface (geological discontinuities etc.)

the worst case decides

friction factor x resultant of vertical forces

cohesion x foundation area

Horizontal joints generally will be the critical planes. The basic condition of sliding stability :

ustpudn UF

coeff. of purpose x resultant of all horizontal forces coeff. of stability x effective sliding resistance

for extreme load (0,9)

class Type of structure Coefficient of purpose

Ia Dams and weirs higher then 5m, control structures 1,2

Ib Weirs up to 5 m, locks, water tunnels, pipelines,... 1,1

Ic retaining walls, canals, ... 1,0

coefficient of purpose –depends on structure purpose and consequences of failure

cdu AcNU

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Overturning stability

0,1stppasstpactn MM

Safety with respect to overturning can be expressed in terms of the moments operating about the

downstream toe of the dam. Mact – sum of overturning moments, Mpas sum of restoring moments

Important for dams, for weirs the sliding stability is generally more important

Uplift stability

0,1stpvstpvdn UF

comparison of vertical force resultants – uplift force, self weight of the construction

critical for the concrete slab of the stilling basin (thin slab x high uplift pressures), possible

measures – drains in the slab with filters (uplift pressure reduction up to 60%),

Weirs Dams

Do not control discharge

Low acceptable fluctuatin of water level

No significant retention effects during

floods (inflow = outflow)

Generally lower

Passage of sediments (gated weirs)

Passage of ice floes

Control of discharge (supply storage)

Wide range of fluctuation of water levels

Flood routing (flood storage in the reservoir)

Generally higher

Sediments settle in the reservoir

No passage of ice floes - ice mlets in the

reservoir

Many features are common for both weirs and dams

Purpose of weirs

Reduction of slope of the river bed, stabilization (reduction of velocity and bed erosion)

Provision of water depth for water intakes

Provision of water head for water power utilization

Provision of navigation depth (river canalization)

Stabilizataion of water surface at optimal levels (agriculture)

Recreation, landscape aesthetics (reduction of fluctuation of water levels in urban areas)

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Basic elements of the fixed weir – cross section

Disadvantages

Water level control not possible

Ice passing not possible

Sediment passing problematic

Uncontrolled backwater during floods

Advantages

Inexpensive, simple

No attendance needed

Integration into nature environment

Application in localities, where the negatives are acceptable or welcome - (regulation of

torrents – bottom stabilization)

head water

tail water weir approach

face stilling basin sill

stilling basin bottom

stilling basin slab foundation joint

sheat-pile walls

riprap

weir crest

weir body

wing wall of weir abutment

spillway profile

expansion

joint

rubble

masonry

Basic elements of the fixed weir – ground plan

wing wall of weir abutment weir body

weir approach

face

sheet-pile walls

stilling basin sill

wing wall of weir abutment

riprap

(weir attachment into banks)

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Basic elements of the gated weir – axonometric view

Partial or complete elimination of negative effects of the fixed weir

More expensive, service personal, high piers, more significant impact on landscape

weir sill (weir substructure)

weir abutment

wing wall of weir abutment

gates

riprap

stilling basin

stilling basin sill

weir piers

upstream

blanket

grout curtain

inspection gallery

bridge

stop logs

store of stop logs

crane

Basic hydraulic design of weir

Weir discharge capacity > design discharge (mostly Q100)

Bazin’s formula

(free and submerged overflow]

23

00 2/

hgbmQ

Q = water flow rate, m3/s

b0 = width of the weir, m

m = discharge coefficient, average 0.45

g = gravitational constant, 9.81

h0 = Height of the water over the weir, m 23

00 2/

hgbmQ z

weir openings

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Classification of fixed weirs

by material

timber weir

boulder weir

masonry weir

concrete weir

combined weir

by the type of construction

vertical wall

roof - shaped

trapezoidal

with rounded crest

streamlined shape

special constructions

(siphon weir, flat-slab-desk

weir)

by permeability

permeable

impermeable

by lay-out

straight skew curved curved broken-line broken-line

Timber weirs

weir with timber pile wall weir with timber grillage with rubble stone filling

“Prague type weir” (mountain streams)

Material – timber : oak, larch, pine tree

Filling– rubble stone with sand-loam

Staroměstský weir (13. century)

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stone facing

riprap

sheat-pile walls

ogee shaped weir

streamline spillway

stilling basin

concrete weir flushing sluice

weir approach

face (stone

paving)

Gated weirs

by operation

manually

operating gear

head water operation

by load transfer

to weir substructure

to piers

to piers and substructure

by control

automatic (water level

control)

semi automatic

(opening)

operating staff

classification of gated weirs

by movement

(ČSN 736513 Weirs)

shutter weirs (flap gate)

vertical-lift gates

radial gate weirs

rolling gate weirs

head water operated weirs

inflatable weirs

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Flap gate weirs

Main bearing structure – curved face plate, curved stiffening face – lenticular hollow box section (torsion stability)

Secondary elements – horizontal support beams (steel shapes), crossbeams (steel plates - ribs)

Side and sill sealing – rubber shapes

Operation – hydraulic motor, pressure oil circuit

lenticular hollow section provisional closure

(needles)

hydraulic motor

(piston)

pin bearing

weir substructure

baffles air inlet pipe

sealed cylinder shaft

inspection gallery

At present, it is the most widely used type of weir shutter for damming heights 3-6 m and span of up to 40 metres.

Perfect functionality, good integration of the weir into the natural environment.

Flap gate weirs

baffles

water inlets (floating,

revision)

air pipe

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Radial (tainter) gates

lifting gate (underflow) x drop gate (overflow)

curved face plate, curved crossbeams (rolled steel shapes), horizontal support beams (steel shapes), horizontal

main beams (welded shapes), radial arms

low torsion stability – double – sided synchronous operation (Gall’s chains)

Side and bottom sealing – rubber shapes

Radial gate weirs are also quite often used because of their efficiency and reliability.

damming heights 3-10 m and span of up to 25 meters

chain

machine room

bearing

arms

main support beams

horizontal support

beams

curved crossbeams

sill crest

Machine room

Machine room (speed reducing transmission)

pinion with Gall’s chain

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Vertical – lift gate

lifting gate (underflow) x drop gate (overflow)

face plate, crossbeams (rolled steel shapes), horizontal main beams (welded shapes)

low torsion stability – double – sided synchronous operation (Gall’s chains). Robust – suitable for sediment bearing rivers

damming heights 3-5 m and span of up to 25 meters

gears

pier groove

machine room

side shield

Poděbrady

Vertical – lift gate (machine rooms)

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Roller gate

Large cylinder (stiffened steel tube) acting as a beam and weir body. Cogged wheels (gear rings) rolling along cogged

rails in inclined pier grooves . Handling by means of lifting chains, belted around the tube at its ends. High torsion stability

– one sided operation.

machine room

cogged rail (rack)

angled groove

bottom shield

(apron)

side shield

typical damming heights 1-3 m and span up to 30 meters

robust construction, prone to vibrations, high material usage, nowadays replaced with more appropriate gates (flap gates)

head water

hinge

flotation

chamber

Hydrostatic pressure operated sector gate

filling valve emptying valve

bearing frame

Hollow gate sections operated with the variable pressure (water level) inside the floating chamber.

curved face plate

curved overflow plate

inspection gallery

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Rubber weir rubber bag filled

with water

filling pipe in concrete

reinforced rubber flange

fixing bolts

fixing

armature

turned-over

rubber sheet

turned-over

rubber sheet

Typical damming heights 1-3 m and span up to 50 meters. Relatively cheap, prone to perforation, shorter lifetime. Often

used at head-race canals, amelioration canals and also as flood protecting gate.

Waterways and navigation

Main advantages of navigation

low resistance to motion - lower fuel consumption

high load capacity and big stowage space

(transport of large and heavy items of goods, raw materials)

low weight of the ship in comparison with the transported load

low crew demands

environment friendly

The use of watercourses and lakes for navigation and also building canals and harbors has developed

since ancient times. Waterways are important element of the overall transport system and have some

specific properties and advantages.

Main disadvantages

relatively slow

low density of the inland waterway network, shortages in

interconnection of particular segments

necessity of linkage to other transportation systems (transloading)

dependence on local natural and hydrological

(discharge, water stages, ice cover, ...)

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study PLANCO Consulting Gmbh (2007)

proportions of cargo-carrying capacity: 1 barge 1500 t = 38 rail waggons à 40 t = 60 trucks à 25 t

TEU = twenty-foot equivalent units (kontejner l = 20 stop)

Types of vessels on inland waterways

Cargo barges – flat bottomed boats, not self-propelled

Open – raw materials etc.

Closed - corn, piece goods etc..

Pushed (towed) by tugs

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Types of vessels on inland waterways

Cargo motor ships - motor + engine hall + fuel tanks = less cargo space

Faster (transport of foodstaff, piece goods)

Closed, open

Types of vessels on inland waterways

Passenger ships

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Types of vessels on inland waterways

Special vessels

floating dredger

floating crane

surwaying boat

Progressive trends - containerization

universal closed ISO container

open

bulk materials

platform tank

refriegerating

Modern trends in traffic are presently reflected, where the piece goods are transported in containers on container ships

for reasons of easier and faster handling.

They can be loaded and unloaded, stacked, transported efficiently over long distances, and transferred from one mode

of transport to another—container ships, rail transport flatcars, and trailer trucks—without being opened. The handling

system is completely mechanized so that all handling is done with cranes and special forklift trucks. All containers are

numbered and tracked using computerized systems.

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Inland waterways

- naturally navigable rivers and lakes or reservoirs (relatively rare, only lower reaches of large rivers –

Rhine, Danube)

- regulated or canalized rivers

- navigation canals

Methods of river regulation and canalization mean improvement of natural conditions in order to

create a useful waterway.

River regulation is required to prevent changes in the course of the stream, to regulate locally its

depth, width, bend radius, and especially to restrict the low-water channel and concentrate the flow in

it, so as to increase the navigable depth during the dry season.

River engineering works

1 - river bank pavement

2 - longitudinal deflecting dike

3,4 – traverse dikes

5 - flow concentrating groynes

Main advantage – the method is nature environment friendly

Main disadvantage – the navigation still remains dependent at hydrological situations (dry seasons)

L-shaped flow concentrating groynes – Elbe near Roudnice (Harke, 2009)

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longitudinal profile of Elbe middle reach w

eir a

nd

lo

ck

we

ir a

nd

lo

ck

River canalization is necessary in the case of small summer discharges and steeper river slopes (generally middle and

upper river branches). Level has to be raised by impounding the flow with weirs at intervals across

the channel, while a lock has to be provided alongside the weir to provide for the passage of vessels.

A river is thereby converted into a succession of pools with nearly horizontal water levels.

Main advantage - canalization secures necessary depth for navigation and lower velocities of water flow

(and also brings the possibility of water energy exploitation)

Artificial navigation canals are man-made channels for water, connected to existing lakes, rivers, or even between seas and

oceans.

Where the bed of the new waterway must change elevation, locks, lifts, elevators or other engineering

works are constructed to raise and lower vessels over a vertical distance.

Either the body of the canal is dug or the sides of the canal are created making dykes. The water for

the canal must be provided from an external source like other streams or reservoirs (water losses due

to locking, infiltration, evaporation).

impermeable canal lining

compacted loam

hydraton (clay, sand, water glass)

sand, soil, cement mixture

plastic sheet

asphalt concrete

concrete

reinforced concrete

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Basic characteristics of the waterway

Width of the straight fairway

B = 2b +3 Db two – way traffic Db = safety distance (3 - 5 m)

B = b +2 Db two – way traffic

Navigation depth draft of the ship + safety margin

d = Tmax + Dt Dt = 0,3–0,5 m (0,5–1 m canals) for international waterways

Hydraulic parameter n n = min 5, better 6.5 – 7 (local 2 – 3 for tunnels, aqueducts)

Underpass height hp

Width modification in bends for R < Rmin Bo = B + DB, DB = L2/(2R+B)

Characteristics based on Classification of European Inland Waterways (7 classes, 1-3 local, 4-7 international)

two-way traffic

Classification of European Inland Waterways

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Structures on waterways

sheet pile walls

Types of side walls

gravity walls L-shaped gravity

walls

U-shaped frame

upper lock approach lower lock approach navigational lock chamber

upper gate

lower head

lower gate

guide wall

side walls

Navigational locks

side

culverts

upper head

tail water

head water

anchor

head (generally < 20 m)

Lock gates

vertical lift gate

flap gate

sinking radial gate

mitre gates

sector gate

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Lock gates

Mitre gates (Hořín) - The gates close against each other at an 18° angle to approximate an

arch against the water pressure on the "upstream" side of the gates when the water level on

the "downstream" side is lower. Opens into side bays.

Flap gate for direct filling of navigation lock

Lock gate of Cabelka’s type

filling position closed position air inlet pipe

sinked gate

filling slot

baffles

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Lock filling systems

Lock filling (emptying systems)

1. indirect - short, middle and long

culverts (by-passes)

2. direct

Hradišťko

long culvert in the wall

filling

openings

valve

valve

valve

valve

Lock equipment

bollards – mooring bits

ladders – up to the chamber bottom, at distance 25 m

semaphores

lighting – at night and poor visibility conditions

dynamic crash protections of gates

central automatic control (control house)

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Boat lifts

Various types of vertical bout lifts

Piston boat lift

Boat lift with

floats

Boat lift with

counterweights

Trough (a box full of water in which a barge can float) moves vertically or sideways up from one

waterway to the other. Counterbalancing by a fixed weight, floats or by a second trough. The motive

power may be electric or hydraulic motor, or may come from overbalancing the top trough with extra

water from the upper waterway.

Piston

Piston shaft

Sealing Control

valve

Sealing

Float Deep shaft

guide - structure guide - structure supporting - structure

Boat lift with counterweights

Strépy-Thieu boat lift, Canal du Centre , Belgium

2002, H = 73 m, 112 x 12 m, trough weight 7500 t

Jean-Pol Grandmont, 2005

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Vertical boat lift with floats

Vertical boat lift with floats Henrichenburg (canal Dortmund-Ems, Germany)

1962, H = 14 m, through 90 x 12 m, 2 x shaft (40 m deep), screw rods

© Raimond Spekking / CC-BY-SA-3.0 (via Wikimedia Commons)

Vertical piston boat lift

Piston boat lift Peterborough (Trent-Severn Waterway, Ontario, Kanada)

1904, H = 19,8 m (highest in the world)

http://upload.wikimedia.org/wikipedia/commons/e/e5/PeterboroughLiftLock23.jpg

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Inclined boat lift

Inclined boat lift (canal Marne - Rhein)

1969, H = 44 m, counterweight 2 x 450 t

Patrick Giraud, 2005