The document summarizes different methods of underpinning an existing foundation to support expansion of a building on the same land plot. It discusses five main underpinning methods: 1) Mass concrete underpinning which involves digging pits by hand and pouring concrete sequentially, 2) Helical piles which use steel shafts with helical flights screwed into the ground, 3) Micropiles which are small diameter drilled and grouted piles, 4) Jacked piles which involve driving steel pipes into the ground with a hydraulic jack, and 5) Bracket piles used for earth retention to support adjacent foundations during excavation. The document also lists potential causes of foundation failure such as poor drainage, weather conditions, poor soil conditions, transpiration

1. CONSTRUCTION TECHINOLOGY 2
CHAPTER : UNDERPINNING
GROUP MEMBERS:
CELINE CHONG
LEE SU WEN
LIM JIA YI
KANG YING HONG
YAP SUK PING

2.  A developer wish to expand his business in K.L city area however
he is required to pay more due to high land prices in the market
nowadays. As an Engineer, he is advised the developer that by
expanding an existing building will provide additional income
and revenue for the developer on the same plot of land.

3. Q1. EXPLAIN FIVE (5) UNDERPINNING
METHODS WHICH ARE TO SUPPORT
FOR AN EXISTING FOUNDATION.

4. 1. MASS CONCRETE UNDERPINNING METHOD
(PIT METHOD)
 Known as “traditional underpinning”
 Strengthens an existing structure’s foundation by digging boxes by hand underneath &
sequentially pouring concrete in a strategic order
 Generally applied for shallow foundation, however, still works very well even at fifty feet (5m) deep
 Heavy machinery is not usually needed - due to the tight nature of the boxes being dug
 Advantages:
1. Low cost of labor
2. The simplicity of engineering
3. The continuity of the building’s use during construction without involving any need of
evacuating the property

5. PROCESS OF MASS CONCRETE UNDERPINNING
 A temporary foundation is
constructed to bear the weight
of the building.
 Existing foundation is relieved
of its weight and can be
worked on.
 Usually done so as to cause
minimal disruption inside the
building.
 The building is then
supported on needle beams.
 A steel l-beam is constructed
at right angles to the existing
foundation, and is pushed into
the existing foundation wall (a
hole is cut for it first).
 Once the beam has been
pushed in, the gap between it
and the foundation wall is
sealed with strong cement
mortar so that the wall can
transfer weight to it.
 Once the temporary
foundation is in place, a pit can
then be dug by hand below
and around the existing
building.
 The existing foundation will
then hang in mid-air.
 The pit method can only be
done if the soil at the site is
a cohesive soil.

6. PROCESS OF MASS CONCRETE UNDERPINNING (CON’T)
 The foundation is then
underpinned by filling the
pit with concrete.
 There be no gap between
the new foundation and
the old.
 As if there is, the building
will settle into this gap,
causing cracks and
damage above.
 Once the concrete has set,
the temporary foundation
can be removed.
 The earth filled in, and the
internal floors repaired and
re-tiled.

7. 2. UNDERPINNING – HELICAL PILES• Helical Underpinning systems are installed to stabilize foundations or
to increase load capacities of existing structures.
• Also known as helical piers
• constructed using steel shafts with helical flights
• The shafts are advanced to bearing depth by twisting them into the
soil while monitoring torque to estimate the pile capacity
• After reaching design capacity, the tops of the shafts are connected
to the structure's foundation.
• Advantages to repairing foundations with Helical Underpinning
systems:
 Installs in limited access sites and low overhead areas
 Quick installation time
 Instant loading – loads may be immediately applied with no cure
time
 Installed with small, commonly used construction equipment
 No spoils to remove
 Minimal to no vibrations or noise
 Built-in quality control – installation torque to capacity correlation
Video:

8. 3. UNDERPINNING - MICROPILES
 Micropiles are deep foundation friction piles constructed using high strength steel casings.
 Micropiles casing generally has a diameter in the range of 3 to 10 inches
 Micropiles underpinning is the process of creating small diameter drilled and grouted friction piles.
 Hollow bars are then installed via the injection bored method to complete the underpinning process.
 Micropiles resist compressive, uplift/tension, and lateral loads and is typically load tested in accordance with ASTM D 1143
(compressive), ASTM D 3689 (uplift/tension), and ASTM D 3966 (lateral).
 Capacities vary depending on the micropile size and subsurface profile. Allowable micropile compressive capacities of more than
500 tons have been achieved.
 Advantages to using the micropile underpinning process:
 Fast and effective
 Drilling and grouting completed at the same time
 Ability to use smaller equipment thus able to work in smaller spaces at a lower cost
 Improves the ground
 Offers a higher skin friction protection

9. 4. UNDERPINNING – JACKED PILES
 This method can be used when the depth of a
suitable bearing capacity subsoil is too deep to make
traditional underpinning uneconomic.
 Jack pile underpinning is quiet, vibration free and
flexible since the pile depth can be adjusted to suit
subsoil conditions encountered.
 The depth attainable by these jacked piles is directly
related to the proof loading the building can sustain.
 It is not recommended for residential housing as this
method relies on the weight of the building to reach
the required loading capacity.
 Steel pipes of 1 metre length ranging from 170mm –
300mm in diameter are then driven down via a
hydraulic jack.
 The pit is then filled with concrete and backfilled.

10. Challenge:
 Expansion and renovation of the historic Michigan State Spartan football stadium required foundation
underpinning.
 The expansion of Michigan State University's (MSU) Spartan Stadium includes construction of new sky
press boxes, elevators and access ramps.
 It is always difficult and challenging to add new loads to an existing structure. The Spartan Stadium project
presented some very significant problems for the entire design/build team. Interference from existing
walls, overhead beams, underground facilities and a complicated existing foundation system created a
and difficult foundation problem.
MICHIGAN STATE'S SPARTAN STADIUM
Jacked Piles:
• The Jacked Piers solution provided exceptional results under challenging conditions.
• Clearance issues were not a problem for installation and the hydraulic pile driving did not introduce
damaging vibrations.
• The ability of Jacked Piers to be arranged in a tight pattern on an existing footing reduced demolition
requirements.
• Capable of carrying more than twice the design load, the Jacked Piers have more than enough capacity to
support a full house of Spartan fans.

11. 5.BRACKET PILE UNDERPINNING
 Bracket piles are typically used in conjunction with earth retention work to
support and/or stabilize existing foundations adjacent to a proposed
excavation
 Be utilized for structures up to two stories high, depending on the weight
of the building and the quality of the bearing material at subgrade or the
new structure.
 When both the existing and future structures belong to the same owner,
the use of bracket piles is very economical
 The steel bracket piles are driven or placed adjacent to the future structure
in pre-augured holes which are then backfilled with a lean sand-cement
mix.
 The load is transferred from the structure into the pile through a steel
bracket welded to the side of the pile.
 A combination of steel plates, wedges, and drypack is installed to ensure a
tight fit between the structure and the bracket
 The spacing of the piles depends on the load distribution in the existing
structure. The maximum spacing should not exceed 8 feet.

12. QB. FOUNDATION
FAILURE AND
CAUSED BUILDING
COLLAPSE

13. 1. POOR
DRAINAGE
 Short downspouts
 The water removed will accumulated on the ground and penetrate into the soil
 Clogged gutters will cause overflowing of the gutters
 Fall leaves, plastic can form clog
 Clean the gutters regularly
 Lack of waterproofing
 Even there is not raining season, water vapor can still penetrate the foundation easily
 Choose right waterproof membrane to install
 Causing
 Uncontrolled water flow
 Cause over-saturation of soil
 Instable of foundation

14. 2. WEATHER CONDITION
Too hot & dry affect the
soil condition by
evaporation. Water
moisture content is low
and the soil is not
compacted well.
Soil will shrink and pull
away from foundation.
The soil and foundation
will move and the
building may collapse due
to the loose and weak
soil.
Shrinking create gaps
between the soil and it is
unbale and weak to carry
the loading of the
superstructure
Soil sink & settle into
ground, the building will
become unstable due to
the uneven foundation

15. 3. POOR SOIL
CONDITION
 Slope failure & Mass wasting
 Movement of earth downhill
 Creep slowly / landslides in a sudden
 The most famous slope failure project is Pisa Tower in Italy.
 Especially expansive clay soil
 The potential of shrink-swell is easily happen and form uneven foundation
 Not recommended soil type
 Absorbing water cause the soil swell by several hundred percent
 Pressure of swelling soil can lift or “heave” building easily
 Soil expands with moisture, contract with desiccation
 Caused up and down movement (different settlement of soil)

16. 4. TRANSPIRATION
 Mature tree and bushes draw the moisture of soil
 The water absorbed will evaporate to the atmosphere so the roots will
continuously absorbed the water underneath the foundation
 A large oak tree can draw 40,000 gallons of water a year up
 Foundation settlement
 The water content in the soil decrease and shrinkage may occur
 Soil shrinkage
 The soil is getting dry so the soil is not compacted well underneath

17. 5. PLUMBING LEAKAGE
Excess water get into
foundation
Soil erosion
Moisture content distorted
Excessive moisture can compact the fill
material under the slab, a void is
created and the slab will settle into the
void
Soil settlement
Soil and foundation will move
Factors affect degree of movement
•Soil type
•Soil density
•Soil moisture content prior the leaks
•Length of time over leak has occurred
Self-checking
Pressure leaks are easy to detect, loss of
water pressure ,increased water bill
Especially for older houses
Cast iron rusting out or a union in the
PVC coming apart.

18. 6. POOR SITE & SOIL PREPARATION
Poor workmanship
Over excavate corners to put concrete
pier in
Excess concrete makes foundation
heavier causing heavier settlement
Unless the pier reach to rock layer
Require soil testing and engineer certification before
and during the construction
Poorly compacted fill
material
Extreme volume changes settlement
Type of soil
•Soft & low-density soil is not
recommended
•Not allow water seep under foundation

19. UNDERPINNING
 It is the process of strengthening the existing foundation building
or structure by extending into subsurface stratum.
 REASON FOR UNDERPINNING
o As a safeguard against possible settlements of a structure when
excavating close to or below its foundation level.
o Construction of a new project with a deeper foundation adjacent
to an existing building.
o Soils that were not properly prepared cannot bear the load and
will consolidate and compact under the weight of the foundation.

20. DESCRIBES THE PROCESS
INVOLVED IN THE
UNDERPINNING WORKS

21. PRECAUTION OF UNDERPINNING PROCESS
3. When the underpinning is complete, the final step involves removing the temporary support system.
2. They make temporary support with steel beams inserted at angles underneath the edges of the foundation.
1. Before underpinning, foundation technicians must set up a temporary support system so they can work safely underneath the
existing structure and foundation.

22. STRUCTURAL REQUIREMENT
• Transfer the vertical load on the existing wall down to the new lower foundation level, and,
• Hold back the horizontal load of the ground, hydrostatic pressure and any other surcharge loads acting
on the outside walls of the basement.
Methods of underpinning:
1. Traditional mass concrete underpinning
2. Reinforced concrete underpinning
3. Multi-stage underpinning

23. WHAT PROCESS
INVOLVED IN THE
UNDERPINNING
WORKS?

24. WHAT PROCESS
INVOLVED IN THE
UNDERPINNING
WORKS?

25. WHAT PROCESS INVOLVED IN THE UNDERPINNING
WORKS?

26. WHAT INVOLVED IN THE UNDERPINNING WORKS?
Video link:
https://www.youtube.com/watch?v=D1FCtfWiSPs&feat
ure=youtu.be

28. CHOOSE ONE OF THE UNDERPINNING METHOD AND STATE THE FUNCTION
OF THAT METHOD IN ORDER TO STRENGTHEN AND STABILIZE THE
FOUNDATION.
Screw Pile:
• Also known as Helical Pile
• A screw like pile which is wound into the ground like a
screw.
• It can be installed quickly and efficiently
• Cost Saving
• They are made of circular hollow steel sections with one
or more helices welded

29. Advantages Disadvantages
Time savings Space needed for
installation
Fireproof Equipment limitation
Minimal cleaned up after
installation
Limiting soil condition
Minimal Site Disturbance Structural Limitation
Easy to Install
ADVANTAGES AND DISADVANTAGES OF SCREW
PILE

30. COMPONENTS OF SCREW PILE
How it Works
• The piles are made of circular hollow
steel sections with one or more helices
attached to them.
• Screw pile is cut into the soil following a
constant pitch, as opposed to auguring
through it.
• The helical flights and shafts are
specifically designed to suit the ground
conditions
• Once the pile reaches its target depth, it
remains permanently in place.
• Concrete is added into it to provide
extra reinforcement to it.

31. How it is Installed
• Screw piles are wound into the ground
like a screw
• It is installed using various earthmoving
equipment fitted with rotary hydraulic
attachments.
• Special drive attachments connect the
screw pile to the machine.
• Incorrect installation techniques are
likely to result in poor overall pile
performance.