CONSTRUCTION TECHNOLOGY

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• CONSTRUCTION TECHNOLOGY
• maintenance

CEM 417
SOURCES FROM slide MOHD AMIZAN MOHAMD MOHD
FADZIL ARSHAD SITI RASHIDAH MOHD NASIR FKA, UiTM
Shah Alam.
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WEEK 2

• Stages for construction

1. Building
2. Retaining walls, Drainage
3. Road, Highway, Bridges
4. Airports, Offshore/Marine structure

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RETAINING WALLS
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WEEK 2

• At the end of week 2 lectures, student will be
  able to
• Identify the different types of retaining walls
  and their respective functions. (CO1 CO3)

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RETAINING WALL

• Basic function to retain soil at a slope which
  is greater than it would naturally assume,
  usually at a vertical or near vertical position

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• Retaining wall failure at the Shin-Kang Dam

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Design of retaining wall

• retaining walls have primary function of
  retaining soils at an angle in excess of the
  soils nature angle of repose.
• Walls within the design height range are designed
  to provide the necessary resistance by either
  their own mass or by the principles of leverage.
• Design consideration
• Overturning of the wall does not occur
• Forward sliding does not occur
• Materials used are suitable
• The subsoil is not overloaded

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Factors which designer need to take account

• Nature and characteristics of the subsoil's
• Height of water table the presence of water can
  create hydrostatic pressure, affect bearing
  capacity of the subsoil together with its shear
  strength, reduce the frictional resistance
  between the underside of the foundation
• Type of wall
• Materials to be used in the construction

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• Failure of retaining wall (dam) due to water
  pressure..

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Types of walls

• Mass retaining walls
• Cantilever walls
• Counterfort retaining walls
• Precast concrete retaining walls
• Precast concrete crib-retaining walls

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Mass retaining walls

• Sometimes called gravity walls and rely upon
  their own mass together with the friction on the
  underside of the base to overcome the tendency to
  slide or overturn
• Generally only economic up to 1.8 m
• Mass walls can be constructed of semi-engineering
  quality bricks bedded in a 13 cement mortar or
  of mass concrete
• Natural stone is suitable for small walls up to
  1m high but generally it is used as a facing
  material for walls over 1 m

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Typical example of mass retaining walls
BRICK MASS RETAINING WALL
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Brick retaining wall
Stone retaining wall
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Typical example of mass retaining walls
MASS CONCRETE RETAINING WALL WITH STONE FACINGS
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Cantilever walls

• Usually of reinforced concrete and work on the
  principle of leverage where the stem is designed
  as a cantilever fixed at the base and the base is
  designed as a cantilever fixed at the stem
• Economic height range of 1.2 m to 6 m using
  pre-stressing techniques
• Any durable facing material can be applied to the
  surface to improve appearance of the wall

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Cantilever wall
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• Two basic forms-
• A base with a large heel
• A cantilever with a large toe

Cantilever L
Cantilever T
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Cantilever walls
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Counterfort retaining walls

• Can be constructed of reinforced or prestressed
  concrete
• Suitable for over 4.5 m
• Triangular beams placed at suitable centres
  behind the stem and above the base to enable the
  stem and base to act as slab spanning
  horizontally over or under the counterforts

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Precast concrete retaining wall

• Manufactured from high-grade pre cast concrete on
  the cantilever principle.
• Can be erected on a foundation as permanent
  retaining wall or be free standing to act as
  dividing wall between heaped materials which it
  can increase three times the storage volume for
  any given area
• Other advantages- reduction in time by
  eliminating curing period, cost of formwork, time
  to erect and dismantle the temporary forms
• Lifting holes are provided which can be utilized
  for fixing if required

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application
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Precast concrete retaining walls
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Pre cast concrete crib-retaining walls

• Designed on the principle of mass retaining walls
• A system of pre cast concrete or treated timber
  components comprising headers and stretchers
  which interlock to form a 3 dimensional framework
  or crib of pre cast concrete timber units within
  which soil is retained
• Constructed with a face batter between 16 and
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• Subsoil drainage is not required since the open
  face provides adequate drainage.

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SUBSOIL DRAINAGE
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• At the end of week this lecture, student will be
  able to
• Identify the functions of various subsoil
  drainage system. (CO1 CO3)

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Drainage

• Effluent- can be defined as that which flows out.
  In building drainage terms, there are three main
  forms of effluent
• Subsoil water water collected by means of
  special drains from the earth primarily to lower
  the water table level I the subsoil clean, no
  need to treat.
• Surface water effluent collected from the
  surfaces such as roofs, paved areas- clean
• Foul or soil water effluent contaminated by
  domestic or trade waste and require treatment

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Source of water
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Building Regulation C2-Resistance to moisture

• Subsoil drainage shall be provided if it is
  needed to avoid-
• The passage of ground moisture to the interior of
  the building
• Damage to the fabric of the building
• Needed for sites with a high water table (level
  at which water occurs naturally below the ground)
• Objective of subsoil drainage to lower the
  water table to a level such that it will not rise
  to within 0.25 m of the lowest floor of a
  building
• Advantages improve the stability of the ground,
  lowering the humidity of the site and improve its
  horticultural properties

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• The water collected by a subsoil drainage system
  has to be conveyed to a suitable outfall such as
  a river , lake or surface water drain and sewer.

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The ideal site
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Typical subsoil drainage details
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Materials of subsoil drainage

• Porous - absorb water through their walls and
  thus keep out fine particles of soil or silt
• Perforated Holes in pipe of different pattern
  which allow water to enter into the pipe and
  channels to a collection points and discharged
  into the designated outlet.

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Suitable pipes

• Perforated clayware BS EN 295-5
• Porous concrete BS 5911part 114
• Clayware field pipes BS 1196
• Profiled and slotted polypropylene or uPVC BS
  4962
• Perforated uPVC BS 4660

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• POLYETHYLENE PIPE

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Perforated pipe
Perforated pipes for footing drains ABS pipe
for downspout drains
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• Subsoil drainage

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Subsoil drainage systems

• The layout of subsoils drains will depend on
  whether it is necessary to drain the whole site
  or if it is only the substructure of the building
  which needs to be protected

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Model of subsoil drainage
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Subsoil drainage systems and drains

• The pipes are arranged in a pattern to cover as
  much of the site as is necessary
• Water will naturally flow towards the easy
  passage provided by the drainage runs

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Herringbone drainage
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Moat drainage
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Outfall to stream or river

• The system is terminated at a suitable outfall
  such as a river, stream or surface water sewer
• In cases, permission must be obtained before
  discharging a subsoil system