kỹ thuật ven bờ biển_các công trình bảo vệ bờ biển.ppt

Kỹ thuật ven bờ biển, các công trình bảo vệ bờ biển,

1. OCEN 201
Introduction to Ocean &
Coastal Engineering
Coastal Processes & Structures
Jun Zhang
[email protected]

2. Coastal Processes
•Typical beach profile and coastal zone
-Beaches dissipate wave energy and are constantly
adjusting to the wave environment (shoaling, wave
breaking, sand bar & surf zone, Fig. 4-1, pp80)
•Littoral Transport (sediment transport)
-Long shore transport (parallel to the shoreline,
long shore current)
-Offshore-onshore transport (perpendicular to the
shoreline)

3. Beach Profile Fig. 4-1, pp102

4. Consequences of Coastal Processes
•Beach erosion (Natural or Man-Made Causes)
Table 4-1 pp104 (old E. pp81)
•Beach Protection & Nourishment
-coastal structures

5. Coastal Erosion

6. Coastal Erosion
Hwy 87
Texas Coast
•Infrastructure
•Property
•Environment

7. Beach Nourishment

8. Economic
value of
Beaches

9. Coastal Processes
•Wind and Waves
•Sediment Transport

10. Coastal Structures
Break waters: (rubble mound, sheet pile, stone asphalt,
Dolos, concrete cassions, floating structures
(coastal & offshore))
•Jetties & Groins (normal to the shorelines)
•Sea walls
Bulkheads, Revetments, G-tubes
•Sand Bypassing (continue the littoral process; passive
and active)
•Ports, Harbors and Marinas

11. Shore Protection Projects-Breakwaters

12. Shore Protection Projects-Breakwaters

13. Shore Protection Projects-Breakwaters

14. Breakwater

15. Waterway
Navigation
Jetties

16. RUBBLE
MOUND
BREAK-
WATER

17. VERTICAL BREAKWATER FIGURES :

18. Design
Considerations

19. Shore Protection Projects-Groins

20. Shore Protection Projects-Groins

21. Shore Protection Projects-Groins

22. Shore Protection Projects-Revetments

23. Different Kinds of Dolos
Concrete & Reinforced Concrete

24. Dolos

25. Various Sea Walls

26. Shore Protection Projects-Seawalls
Construction of Galveston seawall ~ 1902

27. Ports and Harbors

28. New South Wales and Queensland, Australia
Sand Bypass Facility

29. Jetties at the
entrance of
Tweed River
Outlet of the sand pump

30. Laboratory Research
Research Experience
for Undergraduates
(REU) Program

31. Haynes Coastal Engineering
Laboratory

32. Wave Refraction*, Diffraction & Reflection
•Wave Refraction: The direction of waves may
change when they enter from deep to shallow water
or from shallow to deep water.
Deep-1
Shallow-21
 21
21
sin sin
Snells law: , is the phase velocityC
CC


Shallow-1
Deep-21
 2
 2


33. Wave direction is normalto the wave crest
line
Examples of Wave refraction in the costal
zone, see pp 117 Fig 4-21 (old Edition: pp
90 Fig. 4-12).
Wave direction is normal to shore line. In
other words, wave crest-line is parallel to
the shore line.

34. Wave Refraction

35. Phenomena of wave shoaling (wave enters
from deep water to shallow water)
•Wave refraction
•Wave length becomes shorter
•Wave group velocity is reduced
•Wave becomes steeper, which leads to
wave breaking. Wave breaking leads to
the generation of long-shore current.
Definition of the surf zone: from the first
breaker (due to water depth) to the shore
line.

36. General Refraction Analysis22
- Along a ray line, wave direction is always
parallel to it or wave creatline is normal to it.
Wave energy density - Average wave energy per unit length
/8 /2
Wave grou
E gH gA
Ray Line
p (energy) velocity
1
In intermediate water depth
2 sinh2
1
In deep water ,
2 2 2
In shallow water , 1
g
g
g
kh
C nC
k kh
C
Cn
k
C gh C n



  


  
  

37. 1. Steady state (time-independent)
2. Wave characteristics are
inpendent of y
(long shore direction)
3. Bottom contours is
paralell to the shore line
which is striaght

38. 01
0 0 1 1
00
1 0 0 0 0
0
1 1 1 1
1
1
0
0

Subscript '0' denotes it at
1
2
2
gg
gp
gp
gg
C E b C E b
CC
C b C bE
C b C bE
HE
H E




deep water Wave energy flux =
Eenergy conservation (no wave breaking)
g
CE

39. 1
1
0
0
0
1
0
1
, known as the refraction coeff.
, known as the shoaling coeff.
2
SR
R
p
s
g
HE
KK
H E
b
K
b
C
K
C


 pp117-118 (old edition pp91-92)

40. •Wave Diffraction: When wave energy is
transferred laterally to wave direction, this
phenomenon is known as wave diffraction.
Wave diffraction occurs when waves passing
by a surface piercing body. It may occur in
deep or shallow water.
An example in shallow water is wave
diffraction behind a breaker water. See Fig. 4-
22 at pp119 (old edition Fig. 4-13 at pp93).
(internet examples)

42. •Wave Reflection and Transmission: when the
water depth suddenly changes, part of the incident
wave energy is reflectedin the direction opposite to
the incident wave direction, part energy continues
to propagate (transmit) in the incident wave
direction. : incident wave height; : reflected wave height
: transmitted wave height
Reflection Coeff. ;
Transmission Coeff.
ir
t
r
r
i
t
t
i
HH
H
H
C
H
H
C
H



43. 0
0
Reflection Coeff. of a plane slope
tan

/
where is the slope
is the incident wave height
is the wavelength in deep water.
i
i
HL
H
L



Surf parameter Using Fig 4-23 at pp 120 (old edition Fig. 4-14 at pp
94), you may determine the reflection coefficient
based upon the surf parameter.

44. Wave Runup
Wave runup is important to the design of the
height of coastal structure, such as seawalls
and breakwaters.0
Hunt (1959)
tan
for tan 0.1
/
where is the wave runup.
is the wave height
see Fig. 4-24 (p121)
(old edition Fig. 4-15 (p95))
R
H HL
R
H

  

45. Sediment Transport 3
2
s

Buoyancy index: 1
where the specific weight of a sphere
the specific weight of fluid
the diameter of sphere
the kinematic viscosi
ss
s
gd
B
d









50
ty of fluid.
Because the diameter of the sediment is not
uniform, is replace by , which is the
median diameter of the sediment.
is non-dimensional.
s
dd
B

46. Sediment Transport 3
2
3
Buoyancy index: 1
In general, 1, that is, the sediment particle is
heavier than water. The submerged weight of the
particle is proportional to and the falling velocity
decreas
ss
s
s
gd
B
d









es with the increase in viscosity of water.
Hence, smaller buoyancy index indicates smaller falling
velocity and larger buoyancy index results in larger
falling velocity.

47. Based on the buoyancy index, the falling velocity
(also known as terminal velocity) can be
computed using Eq. 4-26 (p125 old edition p101)
or Fig 4-27 (p125) (old edition Fig. 4-18 (p102)).
Falling
f
V
velocity tells the suspension time of a
particle in water after it is suspended in the water
column.
If one knows the current or wave induced particle
velocity, the movement of the particle in the horizontal
direction can be computed.

48. Reading Assignment:
•Sediment Transport & Scour
•Littoral Transport (sediment transport in
coastal or littoral zone)
•Coastal Structure (jetties, groins,
breakwater, sand-bypass & G-tubes)
•Dredging

49. Reading Assignment:
•Sediment Transport & Scour
•Littoral Transport (sediment transport in
coastal or littoral zone)
•Coastal Structure (jetties, groins,
breakwater, sand-bypass & G-tubes)
•Dredging