Retaining walls are an integral part of any sea facing structure or structures which contain single or multiple basements. The PPT gives a general idea about retaining walls and also focuses on a case study of the retaining wall along the Worli Seaface in Mumbai, India.

1. RETAINING WALLS
CASE STUDY: WORLI SEA FACE

2. TOPICS COVERED:
(1) GENERAL STUDY OF RETAINING WALLS
(2) STUDY OF SEA WALLS
(3) SITE STUDY : WORLI SEA FACE
(4) SITE PICTURES
Batter
Drainage
HoleToe

3. A GENERAL STUDY OF RETAINING WALLS
Retaining walls are usually built to hold back soil
mass. However, retaining walls can also be constructed for
aesthetic landscaping purposes.
Gravity retaining wall
GL1
GL2
BACK
SOIL
Shown alongside is the
broad classification of the
different types of retaining
walls.
(1) Gravity walls
(2) Piling walls
(3) Cantilever walls
(4) Anchored walls
The additional categories
are indicated in the flow
chart.

5. APPLICATIONS OF RETAINING WALL
 A RETAINING WALL MAINTAINING THE DIFFERENCE
BETWEEN THE ELEVATIONS OF THE GROUND
SURFACE.
 RETAINING WALL OF
A BASEMENT

6. APPLICATIONS OF RETAINING WALL
 A TUNNEL PORTAL
 MAINTAINING THE
LEVEL BETWEEN A
HIGHWAY AND A
CONTOUR LAND

7. WHAT IS EARTH PRESSURE?
 Earth pressure is the pressure exerted by the retaining
material on the retaining wall. This pressure tends to
deflect the wall outward.
 Types of earth pressure :
 Active earth pressure or earth pressure (Pa)
 Passive earth pressure (Pp).
 Active earth pressure tends to deflect the wall away from
the backfill.
 Passive earth pressure is the highest limiting lateral
pressure developed at the onset of shear failure by wall
moving in the direction opposite to the direction of
acting earth pressure
Pa
GL
Variation of Earth pressure
PP

8. TYPES OF FAILURES IN
RETAINING WALLS

9. INTRODUCTION TO SEA WALLS
 Seawalls are generally massive concrete structures emplaced along a considerable
stretch of shoreline at urban beaches.
 The rubble mound seawall is generally designed to consist of three layers. Viz.
core, secondary layer and an armour layer (Fig.1). A minimum of two layers of
stones (units) in the armour and secondary layer is always necessary. While the
thicknesses of these layers are determined by the size of stones used, the levels
including that of the core are determined based on maximum water level, design
wave height, wave run-up, permissible overtopping and method of construction.
Seawalls are vertical or near
vertical shore-parallel structures
designed to prevent upland
erosion and storm surge flooding.

10. NEED FOR SEA WALLS
 The best natural protection against erosion is an adequate beach on which waves expend their energy.
Creation of beach is rarely possible due to economic reasons. As such, the engineering structures like
seawalls, revetments, offshore breakwaters, etc. are adopted for coastal protection. Rubble mound seawall
is more commonly used measure in India for combating coastal erosion.
 Various methods to prevent beach erosion are briefly indicated below :
 (a) Seawalls, revetments, anti-sea erosion bunds
 (b)System of jetties – shore connected
 (c)System of offshore breakwaters - away from the shore

11. DESIGN DETERMINATION OF SEA WALL
 Position of the seawall
For locating the seawall, determination of the
beach profile and the water levels are
important. The highest and the lowest water
levels at the site must be known before evolving
a design. The highest water level helps in
deciding the exact crest level while the lowest
water level guides the location of the toe. The
bed slope in front of a coastal structure also has
an important bearing on the extent of damage
to the structure and wave run up over the
structure. With steeper slopes, damage to
armour stones is more as compared to flat bed
slope. The wave run-up is also higher on steep
bed slopes.
 The seawall should be located in such a position
that the maximum wave attack is taken by the
armour slope and the toe.

12. Advantages Disadvantages
•Long term solution in comparison to soft beach
nourishment.
•Effectively minimizes loss of life in extreme events and
damage to property caused by erosion.
•Can exist longer in high energy environments in
comparison to ‘soft’ engineering methods.
•Can be used for recreation and sightseeing.
•Forms a hard and strong coastal defense.
•Very expensive to construct.
•Can cause beaches to dissipate rendering them useless
for beach goers.
•Scars the very landscape that they are trying to save and
provides an ‘eyesore.’
•Reflected energy of waves leading to scour at base.
•Can disrupt natural shoreline processes and destroy
shoreline habitats such as wetlands and intertidal
beaches.
•Altered sediment transport processes can disrupt sand
movement that can lead to increased erosion down drift
from the structure.

14. AN OLD MAP OF MUMBAI

16. LOCATION OF SITE:

17. WORLI SEAFACE :
(1) ONE OF THE SEVEN ISLANDS OF OLD BOMBAY,
WORLI IS CURRENTLY A PART OF SOUTH
MUMBAI, EXTENDING FROM HAJI ALI TO
PRABHADEVI.
(2) THE BRITISH HAD ESTABLISHED A FORT IN
THIS AREA: THE WORLI FORT, IN AROUND
1675. SINCE THEN WORLI SEA FACE HAS BEEN
STRATEGIC FOR NAVAL SECURITY.
(3) WHILE THE GRAVITY RETAINING WALL AT THE
SEAFACE DATES BACK TO THE SAME TIME,
RENOVATIONS IN TERM OF VALUE ADDITION
HAVE BEEN DONE FROM TIME TO TIME.
(4) FOR EG. THE DEVELOPMENT OF A
PROMENADE AND RECENTLY, THE
TETRAPODS(LIKE IN MARINE DRIVE) WERE
ADDED IN WORLI SEA FACE ABOUT 3 TO 5
YEARS BACK.

18. SCHEMATIC SECTION:
 The schematic section of the wall shows the type of
retaining sea wall constructed.
 The aim of constructing this wall was to protect the
shore from erosion and to protect areas of human
habitation, conservation and leisure activities.
 Concave structure introduces a dissipative element.
 The curve can prevent waves from overtopping the
wall and provides extra protection for the toe of the
wall
 Curved seawalls aim to re-direct most of the incident
energy, resulting in low reflected waves and much
reduced turbulence.

19. SITE PICTURES

20. A tetrapod is a four-
legged concrete structure
used as Armour unit on
breakwaters. The
Tetrapod's shape is
designed to dissipate the
force of incoming waves
by allowing water to flow
around rather than
against it, and to reduce
displacement by allowing
a random distribution of
tetrapod to mutually
interlock.

21. The random rubble piles
are a toe protection
measure for the retaining
wall.

22. The original stone retaining wall is strengthened with concrete
and clad with a 1-meter wide granite stone seat. This feature
has made the stretch a popular hang-out spot, rather than just
serving the purpose of being a retaining wall.

23. One can clearly see the gravity-type stone retaining wall, which
was presumably constructed by the British. The concrete
layering is distinctly visible.

24. The junction where the
retaining wall meets the
Bandra-Worli sea link
terminal

25. Sea level rise creates an issue for seawalls worldwide as it raises both the
mean normal water level and the height of waves during extreme weather
events, which the current seawall heights may be unable to cope with

26. NEW TECHNOLOGIES
 In 2011, the BMC had proposed the revitalization of the
shores between Mahim and Worli by extending the
beachfronts from 3 m to 50 m.
 The existing seafronts would be protected by employing
GEOTEXTILE BAGS. These are sacks filled with sand,
which will be set up linearly along the shore, leaving
some place for the sand to accumulate in the desired
shoreline.
 The main applications are:
 • flood control and protection
 • reinforcing existing dikes/shoreline structures
 • erosion control
 • storage of contaminated sediments
 Geo-textile bags are produced from woven textiles with
very good filtration properties and high tensile
strengths that will resist to pump pressures, handling
and total weights.

27. THANK YOU
GARIMA RAJPUT 41
MANASVI RANE 42
RITHIKA RAVISHANKAR 43
SHIVALI SANAP 44
SUVOJIT SEN 45