Post on 19-Dec-2021
Design of a Permeable
Concrete Block Retaining WallPresenter: Cosmo Farinola – Cardno
Introduction
Presentation overview
What is a permeable
concrete block retaining
wall?
Details of permeable
concrete blocks
Designing a permeable
concrete block retaining
wall
Massbloc wall projects
Questions
What is a Permeable Concrete Block Retaining wall
Consists of large permeable precast concrete blocks that interlock to create a gravity retaining wall structure
The system was originally developed in New Zealand in the early 1980’s and was launched by Rocla in Australia in 2002 as the Rocla MassBloc retaining wall system
The blocks have been used in bridge abutments, road embankments, highway stabilization and general retaining walls up to 6.0m in height
The blocks are laid without mortar and are interlocked by a nib at the base of each standard block
Cardno was engaged by Rocla to prepare design and construction details and has an ongoing relationship
Details of a permeable concrete block wall
Large concrete blocks that are
1000mm high x 1190mm wide x
900mm deep
The base unit forms the bottom
row of the wall and has no nib and
a block weighs 1.7tonne
The standard unit has a nib (170
wide) at the bottom of the block
that overhangs the block below
resulting in the interlocking. A
standard unit weighs 1.9tonne
Blocks can be manufactured with
varying height and width up to the
above stated dimensions and a
variety of colours
Details of a permeable concrete block wall
Blocks are unreinforced and are
supplied with a 5.0 tonne lifting
anchor
The wall steps back 170mm for
each metre height due to the nib
interlocking
Solid blocks (20MPa) are also
available for load bearing
applications
Details of a permeable concrete block wall
Walls can be constructed with a 90
degree maximum change in
direction using half blocks
Details of a permeable concrete block wall
Walls can also be constructed to a
curvature or radius
Details of a permeable concrete block wall
The permeability of the block
unit and mortar free joints
assists in relieving water
pressure from behind the
wall but as with all good
retaining wall construction
practice it is recommended
that adequate drainage is
provided to the rear of the
wall
Designing a Permeable Concrete Block Retaining Wall
A Massbloc retaining wall is a gravity wall designed in accordance with the requirements of AS4678-2002 Earth Retaining Structures and AS1170.0 & AS1170.1 -2002 Loading Codes
The wall is generally designed using Coulomb Theory and is checked for overturning, sliding, bearing and global stability.
Loads to be resisted by the wall generally consist of horizontal earth or water pressures and vertical surcharge loading to the rear of the wall, if applicable.
The parameters required to carry out the design normally consist of the following:
I. Backfill material
II. Total wall height
III. Maximum backfill slope
IV. Wall classification in accordance with AS4678-2002
V. Maximum surcharge loading
VI. Subground bearing pressure
VII. Φ = internal friction angle of soil
VIII. C = characteristic cohesion of soil.
Designing a Permeable Concrete Block Retaining Wall
Depending on the location and use of the wall it may also be required to be
designed for Earthquake forces
A computer program has been developed by Cardno for Rocla for the design of
Massbloc retaining walls and is able to be downloaded for free from the Rocla
website. The program utilizes the above parameters.
The computer program has a maximum wall height of 6.0m and wall heights
greater than 6.0m will need to be checked by using first principles.
No fines concrete (concrete without fine aggregate) can also be used as backfill
material to increase the depth of the wall and allow for greater retaining height
provided the usual checks are carried out.
Designing a Permeable Concrete Block Retaining Wall
Designing a Permeable Concrete Block Retaining Wall
Massbloc Wall Projects
• Blayney Bridge
Abutment
Massbloc Wall Projects
• Mining application
Massbloc Wall Projects
• Lake Eacham,
Cairns
Massbloc Wall Projects
• Mt Hotham Ski fields
Massbloc Wall Projects
• Hunter Expressway
• Note solid blocks
Questions?