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So, basements can provide ............space in
a building and thereby enhancing the
............. of occupants.
additional
quality of life
What are the issues arising during
excavation works?
1.What are you going to find during excavation
2.Temporary/permanent soil support
3.Keeping the water out!
3. Methods for basement construction
Open excavation
Bored pile walls (Contiguous Piling )
Diaphragm Walling
Open excavation
• Using open excavation with temp support usually
steel sheet piles
• Sides being battered to angle of repose
• Construction is carried out and then …
• Backfill after construction
Interlocking sheet piling • Interlocking steel sheet piles driven
into ground
• To obtain continuous barrier in the
ground so that permanent work can
proceed
Methods
• Sheet piles driven into ground
• Excavation between steel sheet
piling in stages
• Ground anchors installed at
regular intervals
• Excavation to formation level
• Basement construction
• Steel sheet can either be
withdrawn or left in as permanent
ground water control
Interlocking sheet piling
Advantages
• Watertight
• Safe
• Quick
• Suitable for
congested site
• Suitable for deep
excavation
• Simple, less
obstruction
• Suitable for most
soil types
Disadvantages
• Noisy
• Not economical for
big one-off project
Bored Piling
• Similar to
diaphragm wall
• Closely spaced
precast/ bored
piles are used to
form perimeter
retaining walls
• Diameter varies
from 300-600 mm
Bored Pile walls
piling rig in Continuous
Flight Auger (CFA)
mode
The range of CFA piles is between
300mm and 1200mm in diameter and
can be created up to 30 meters long.
Rotary Bored Piling
piling rig in rotary bored piling
mode
For larger diameter piles up to
3000mm rotary flight auger systems
can be used, but these are not
continuous flight and the soil has to be
brought to the surface in sections.
Diaphragm Walls
Diaphragm walls are typically 20m to 50m deep, but may extend to
considerably greater depth.
Retaining walls construction
Diaphragm Walls
Retaining walls construction
Advantages • Watertight
• No underpinning of adjacent
properties necessary
• No noise / vibration problem
• For congested site
• For deep excavation
• Min.movement of pavement,
road and services
• Can form part of basement
structure
Disadvantages
• Mud sediment at trench base might
not be displaced completely by
concrete
• Finished walls in gravel soils
expected to be rough
• Uncertain quantity of concrete
needed
• Larger tolerance of concrete cover
is necessary
• Concrete to be placed continuously
to avoid trapping mud in the body of
wall
• Construction is slow / can be
expensive
Responsibilities for safety, quality and the environment
Risk management
Working platforms
Pile trimming
Essential design requirements
Ground conditions
Workmanship
The image below shows various water penetration points. Nearly every one
of these are present in the modern basement in some form or another.
• Waterproof membrane materials:
– Mastic asphalt
– Polythene sheeting
– Bituminous compound
– Epoxy resin
– Bitumen laminates
Tanking Method