Construction Technology II (Seminar) - Deep excavation

1. Deep
excavation
Lee Siaw ChyI
0330451
Carolyn Low Sing Yee 0327652
Wan Yee Len
0330764
Wong Yong Le
0326478

2. List out the types of construction
method for deep excavation.
1. Open Cut
2. Bottom-Up
3. Top-down

3. Choose (1) type of
construction
method for deep
excavation and
explain the
sequence of
construction.
Top-down method
1) Install retaining wall, piles and basement
columns.
2) Struts are installed
3) Cast the basement top slab and beam.
4) Excavate the soil underneath and start construct
above.
5) Construct the 2nd basement slab while work above
ground continues.

4. Two (2) major
design
consideration
for deep
excavation.
• Planning of subsurface
investigation and laboratory testing
•Evaluation of foundation of
adjacent properties and their
tolerances

5. Two (2) importance of
implementing
excavation support
systems.
● To assess on the cost and time of
construction.
● To ensure that movements will not cause
damage to neighbouring structures or to
utilities in the surrounding ground.

6. This is a photo of excavation support system
for the Getty Center art museum garage in Los
Angeles, California. The excavation is about 75
feet deep. The sides of the excavation are
supported by soldier piles and lagging. The
soldier piles were driven before excavation
began, and the wood lagging were installed as
the excavation proceeded down. On the sides
of the excavation the soldier pile and lagging
wall is supported by post-tensioned anchors
drilled and grouted into the soil around the
excavation. The corners were supported by
corner braces.
Example

7. Explain
with a
sketch why
cantilever
wall is only
suitable for
shallow
excavation.
BASEMENT FLOOR LEVEL
GROUND LEVEL
ACTIVE EARTH
PRESSURE
- SOIL PRESSURE
- HYDROSTATIC
PRESSURE
PASSIVE
EARTH
PRESSURE
RETAINING
SIDE
EXCAVATED SIDE

8. Before excavation, the pressure is in
equilibrium state.
An imbalanced load situation is created when
the soil is unloaded on the excavated side.
EXCAVATED
SIDE
RETAINING SIDE

9. BASEMENT FLOOR LEVEL
GROUND LEVEL
ACTIVE EARTH
PRESSURE
- SOIL PRESSURE
- HYDROSTATIC
PRESSURE
PASSIVE EARTH
PRESSURE
RETAINING
SIDE
EXCAVATED SIDE
>18ft (6m) deep

10. Two types of additional support and their
advantages and disadvantages.
1. Ground Anchor
● Earth, percussion driven or mechanical anchors
● Hold, restrain and support building, civil engineering and other structures

11. Advantages
● Minimal disruption to surface
finishes while installing
● Able to hold capacity up to
3000kN
● Lightweight and corrosion
resistant
● Provides a clean area for the
construction of basement
Disadvantages
● Requires specific equipment and
professional engineers to
operate.
● Difficult to apply anchors in great
depth
● Great care must be taken to
prevent movement of ground
anchors and wall

12. 2. Rakers
● Temporary support to unsafe
wall
● Also known as inclined shore,
varies with site condition
● Transfers floor and wall loads
to ground

13. ● Difficult to assemble
● Must only rest against solid
masonry
● More secure compared to
other additionals supports
● Suitable for soft ground
area because the sole
piece area can be
increased
● Can be used for taller
houses
Advantages Disadvantages

14. Two (2) reasons for selecting interlocking steel sheet
piles as supporting system.
● Durable and Long lasting
○ Interlocks allow individual sections to be
connected continuously
○ Continuous steel wall that is earth tight
and water resistant
● Convenient and Easy to install
○ Readily available and transportable