Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 7 RETAINING WALL
7.6.2 Types of Flexible Walls
The following retaining wall types are commonly used in Malaysia either to retain and/or support
soils during excavations:
a) Sheet pile wall
b) Soldier pile wall
c) Contiguous bored pile / caisson wall
d) Diaphragm wall
a) Sheet Pile Walls
The sheet pile wall is used in many types of temporary and permanent structures. It is one of the
most common methods used in the Department especially for the support and protection of river
banks, water front construction, flood defence as well as temporary supports or containment for
construction of hydraulic structures. Steel sheet piles are preferred mainly because of their ease of
installation, length of service life and ability to be driven through water. However, they are not
suitable when high bedrock or boulders prevent penetration to the required depth.
When selecting sheet piles to be used, it is important to consider the drivability of the piles. The
ability of the sheet pile to penetrate the ground depends on the section size of the pile and the type
of the pile hammer used, as well as the ground conditions. It is difficult to drive sheet piles through
soils with Standard Penetration Test (SPT) ‘N’ values greater than 50 (subjected to pile section).
Further discussion on the basic principles in design of sheet pile wall are discussed in Item 7,6.3
below.
b) Soldier Pile Wall
Soldier pile wall has two basic components, soldier piles (vertical component) and lagging
(horizontal component). Soldier piles provide intermittent vertical support and are installed before
excavation commences. Due to their relative rigidity compared to the lagging, the piles provide the
primary support to the retained soil as a result of the arching effect. Spacing of the piles is chosen
to suit the arching ability of the soil and the proximity of any structures sensitive to settlement. A
spacing of 2 – 3 m is commonly used in strong soils and no sensitive structures are present. The
spacing is reduced to 1 – 2 m in weaker soils or near sensitive structures.
c) Contiguous Bored Pile /Caisson Wall
Replacement pile wall i.e., contiguous bored pile wall or caisson wall is the common excavation
support system adopted in Malaysia. Generally, these types of wall are used as the permanent
retaining wall system for basement construction and sometimes for high wall in hillside
development.
Bored piles or caisson piles are constructed continuously in a row to form retaining structures. A
gap of approximately 75mm to 100mm is allowed between the piles. for ground with high ground
water table or loose soils, grout columns are introduced between the gaps behind the wall system.
For a better water tide conditions pressured grout columns can be used to minimize the water
leakage.
For caisson wall, it is commonly used at areas with limited working space; where big machinery i.e.,
boring rig and excavator are not possible.
7-26 March 2009