Echo Prestressed Hollow-Core Walls

A name truly cast in concrete

Prestressed Hollow-Core Walls RETAINING WALLS

SECURITY WALLS

ECHO PRESTRESSED HOLLOW-CORE RETAINING WALLING (EPRW®) THE CANTILEVERED

stand minor deferential settlement without

WALL SOLUTION

incurring structural damage.

This concept is a freestanding EPRW®

Gravity walling can be constructed in al-

with no lateral support at the top end of

most any situation where a rapid grade

the wall and no mechanical soil stabilisa-

change is desired. Gravity walling confines

tion. These walls cantilever loads to large

the soil or other fill material as a reinforc-

structural footings, converting horizontal

ing mass. This walling solution can also be

pressures from behind the wall to verti-

used in cut-and-fill applications.

cal pressures on the ground. The walls require rigid concrete heel-and-toe footings

INTRODUCTION A retaining wall is a structure designed and constructed to resist lateral soil pressure

which are cast below ground to resist the

GRAVITY WALL

overturning moment. This design limits

DESIGN CONSIDERATIONS

the height of the wall to 5,0m maximum.

A gravity retaining wall must have sufficient weight and width to prevent ex-

THE GRAVITY WALL SOLUTION

ternal forces from overturning or shifting the wall. The wall must form an integral

when the desired change in ground elevaGravity retaining walls are constructed on

whole, ie, the individual slabs must func-

and with soil stabilised with man-made

tion as a single unit to create a wall suf-

Two basic design concepts – CANTILEVER

materials. This type of structure is able to

ficiently stable to handle the external

and GRAVITY - are used for the construc-

retain the earth behind it by virtue of its

forces that might cause it to collapse and

tion of Echo prestressed hollow-core retain-

weight. Gravity retaining walls have a de-

the internal forces that might cause it to

ing walls.

gree of flexibility that allows them to with-

lose shape.

tion exceeds the soil’s angle of repose.

01 | prestressed hollow-core walls

EXTERNAL STABILITY External stability of an EPRW® is achieved by designing to four potential external failure modes: • Global stability

: FSgl=1.5

• Base sliding

: FSsl=1.5

• Overturning

: FSot=2.0

• Bearing capacity

: FSbc=2.0

INTERNAL STABILITY Internal stability refers to the capacity of individual Echo prestressed hollow-core slabs forming a single integrated wall.

ADVANTAGES

The wall must be designed so that the individual slabs do not pull out, separate, or slide apart.

This is achieved with either of the following options.

substantial

• Echo offers full turnkey retaining or se-

site labour. This wall solution is three

times faster than traditional in-situ

construction.

and reinforcing configurations can be

Grouted joints with key-formed

slab edges.

varied to suit wall height and load

Tongue-and-groove (T&G)

interlocking profiles.

Normative referee

• Openings for air conditioning ducts

SANS 207: 2011, Edition 1

and other services are easily accom-

•

Controlled factory production yields du-

The Echo Prestress retaining wall (EPRW®)

rable and aesthetically pleasing finishes.

concept, either on its own or in combina-

•

Panels can retain fill material up to 10m

tion with geogrid is as effective as more

as specified by the principal engineer.

walls; modular-block walls; or gabion basket walls.

SANS 10400-K: 2011, Edition 3 SANS 10400-H: 2012, Edition 3

modated.

walls; steel-reinforced concrete retaining

curity wall solutions.

requirements.

costly alternatives such as: cast in-situ

development

• Efficient light-weight sections. Depth

for

• Increased productivity and reduced on-

1) Echo’s standard edge profile:

2) Echo’s adapted edge profile:

land

purposes.

• Unlike retaining block walls, which are

constructed at an angle, prestressed

walls are 100% vertical, thus saving

SANS 10400-A: 2010 SANS 10400-B SANS 10400-H SANS 2001 – CC1:2007 Edition 1 BS 5896 BS 8002 BS EN 1897 BS EN 13738 SANS 1200 D SANS 2001 SANS 10100-1

Cores filled solid in the factory for 100mm

Wall heights up to 5,0m are possible with this design configuration.

Add geotextile and heights of 6-7m walls are possible

SANS 10100-2 SANS 10162-1 SANS 10162-2.

Lifting hooks

Trowel finish this side

Fairface finish this side

Sub-soil drain to be built by specialist

Mo

me

Starter bars cast on site as per engineer’s design

nt

con

Grouting pockets at 200mm centres for pouring of nonshrink epoxy grout, SIKA 212 or similar approved by the principal engineer nec

tion

ach

iev ed

Foundation size according to principal engineer’s design

A TYPICAL SECTION THROUGH A VERTICAL HOLLOW-CORE RETAINING WALL

02 | prestressed hollow-core walls

HANDLING ORIENTATION

- VERTICAL A 10m high wall requires intermediate support Height of wall in m (meters)

250mm Echo wall panel

Water proofing by specialist

10.0 6.0 4.8 3.6 2.4 0

120 150 200 250 250 Wall slab depth in mm (millimeters)

ECHO PRESTRESSED HOLLOW-CORE SECURITY WALLS (EPSW®)

INTRODUCTION 150 mm

Echo security walls are not comparable

120 mm

Column flanges

with other walling products. In a class of their own, they protect high-value 120 mm Echo T&G wall

properties of strategic significance such as airports, military bases, industrial and

Fair face finish

commercial parks, mines and prisons – in fact any operation that requires over-

Wall panels are wedged and grouted into the column flange

the-top security. 50MPa concrete and prestressed steel on both sides of the

Steel column sizes are adapted to suit wall height, wind and soil conditions

Heights up to

walls. Handling orientation is horizontal and panel jointing is based on a tongueand-groove shear-key connection.

4.8 m possible

panels ensure robust and impregnable

Bolts to engineer’s specifications Base plate designed according to principal engineer 250 mm Echo solid precast base slab. Alternatavely a column base can be cast in-situ.

Natural ground level

Lifting hooks cast in base slab

50 mm river sand blinding

95% Mod AASHTO density

A TYPICAL SECTION THROUGH A HORIZONTAL HOLLOW-CORE SECURITY WALL

03 | prestressed hollow-core walls

ADVANTAGES

HANDLING ORIENTATION

• The soil quality - suitable for soil

1) This is the only precast concrete wall

conditions with a minimum 100KPa

constructed with 50MPa concrete and

bearing pressure.

reinforcing on both sides of the panels.

• Wall panels are typically 120mm or

Echo walls are virtually impregnable

150mm deep.

and cannot be scaled or broken without

• Wind resistance (Project specific).

generating considerable and detectable

• Water drainage weep holes supplied

disturbance.

by Echo.

• Typical centre-to-centre dimension

2) Speed

is 6.0m.

of

construction

beats

con-

ventional brick or in-situ methods.

• Wall accessories (razor wire; electric

wires, cameras etc).

3) Wall panels can be dismantled and re-

• Height specifications vary from 2,4m –

used because they are not grouted

4,8m with a 0,6m section below ground

but assembled with tongue-and-groove

for added security.

shear key joints instead.

04 | prestressed hollow-core walls

- HORIZONTAL

The support columns are based on a cantilevered design Height of wall in m (meters)

DESIGN CONSIDERATIONS

6.0 4.8 3.6 2.4 0

120 120 150 150 Wall slab depth in mm (millimeters)

Echo Prestress (Pty) Ltd

|

Part of the Echo Group of Companies

Hollow-Core Concrete Floors and Walls Cnr. Hytor & Chloor road, Chloorkop

|

Private Bag 1, Edleen, 1625

T: 011 589 8800

|

F: 011 589 8955

E: sales@echo.co.za

|

W: www.echo.co.za

GPS: 26 03 59.7 S 28 10 48.7 E

lasting value of choice

international prestressed Hollowcore association

Echo Prestressed reserves the right to alter any of the details contained herein without prior notice. Š Echo Prestress (Pty) Ltd 2014. Issue No1.