The discussion on rehabilitation of foundations were discussed. The types used for rehabilitation were explained with the procedure. in addition, the case study under each type were also discussed for better understanding of the subject.

1. Presented by

2.  Foundations are sub-structure that transmits the load of the building
along with its own weight into the soil.
 The main purpose of the foundation is to increase the stability of the
structure by distributing the structural load over a large bearing area
without causing bearing capacity failure and excessive settlement.

3. (1) BEARING CAPACITY FAILURE:
1. By error in estimation of Shear Strength parameters
2. By error in estimation of Type of Shear failure in SBC determination

4. (2) SETTLEMENT:
 Settlement of foundation is when the
weight of the structure is greater than
the bearing capacity of the soil.

5. (3) SHRINKAGE CRACK:
The basic reason for the development of
shrinkage cracks in concrete slab-on-
grade foundations is due to ground water
depletion.
Found on clay soil and cracks are
developed in foundation wall and floor slab.

6. (4) MOISTURE INSTRUSION:
Moisture penetrates the foundation
at the location of the shrinkage cracks.
It also penetrates the slab in the form of
water vapor and cause damage to floor
coverings and settles.

7.  Foundation is an integral structural part of a home and affects the
building from the basement to the roof if it is weekend or fail.
 If the foundation fails and no foundation repair is made, the rest of the
home will ultimately crumble.
 Rehabilitation is a process that strengthens foundations which have
been weakened by above discussed factors.

8. 1. Concrete jacketing
2. Micropile technique
3. Push pier system
4. Jack up technique

9.  Commonly used method for widening and strengthening of existing
foundations.
 Carried out by constructing a “concrete jacket” to existing
foundation.
 With this method, axial strength, bending strength and stiffness of the
damaged column gets increased.
 The size of the jacket shall be selected such that the average
maximum foundation pressure does not exceed the recommended
allowable value.
 The new jacket should be properly anchored to the existing footing in
order to withstand transfer of loads.

10. STEP 1: Excavation around the
footing.
STEP 2: Cleaning and roughening the
concrete surface.

11.  STEP 3: Installing dowels at 25-30cm
spacing in both directions using an
appropriate epoxy material.
STEP 4: Fastening the new steel bars.
STEP 5: Pouring the new concrete.

12. INSTALLING DOWELS AND STEEL
RODS
JACKETING

13.  Micropiles are small-diameter (typically 2” to 8” diameter) piles that can be
drilled, sealed and injected with cement grout and incorporating steel
reinforcement elements that withstand a higher proportion of all the design
loads compared with conventional piles.
 Can be vertical or inclined.
 Can be installed in confined space and through any type of subsurface
condition from sand to clay.
 The load is mostly supported by the steel and transferred via the cement
grout to the surrounding ground through high lateral resistance.

14. 1. Drilling and casing
2. Reinforcement placement
3. Injection (grouting)
4. Connecting to the superstructure.

16. PROBLEM:
The expansion of Michigan State University’s Spartan Stadium includes
construction of new sky boxes, press boxes, elevators and access ramps.
However, some of the new load from these improvements will be transferred to
existing columns and footings. MSU’s consultants determined that the existing
footings were too small to carry the additional load and that foundation
modifications would be necessary.
SOLUTION:
Micropiles were chosen to structurally support the existing footings and
to transfer the new loads to bedrock.

18. Push piers are hydraulically driven pier systems consisting of sections of
galvanized or epoxy-coated steel pipe.
These systems utilize high-strength round steel tube sections and a load
transfer bracket to stabilize and to lift sinking or settling foundations.
Push piers has its ability to penetrate various layers and strengths the soil
to achieve great depths. An important feature that makes this possible is called
a “friction reducing collar” which is simply a ring that is welded to the pier
segment.
The friction reducing collar slightly enlarged end creates a small annular
space around the pier shaft that can dramatically reduce skin friction as the
pier is advanced through the soil.

20. STEP 1: Footing is exposed for the bracket.
STEP 2: The bracket, driving equipment
and tubes are assembled at pier
location.

21. STEP 3: Steel tube sections are hydraulically
driven into soil.
STEP 4: Weight of the home is transferred to
the piers.

23. STEP 5: Lifting the structure back to its
original position is attempted.
STEP 6: Soil is backfilled and work area is
cleaned up.

24. PROBLEM:
The liberty middle school in Clifton is a single storey structure with exterior concrete block walls
and brick veneer. A bump-out area of the building approximately 100 feet long and 14-feet wide had
settled and rotated away from the main footprint of the structure. An interior block partition wall
intersected the long exterior wall at its mid-length. The settlement and rotation of the exterior wall
caused the two walls to separate with the crack wider at the top than the bottom. The movement
also raised concern that connections and adequate bearing of the roof joists to the top of the
exterior block wall had been compromised. A subsurface investigation encountered lean to fat clay
underlain by competent limestone.
SOLUTION:
A system of hydraulically-driven push piers was selected as the most economical
method to stabilize and potentially lift the settled area of the building. A total of 17 push piers were
installed at a 7 feet maximum center-to-center spacing. 15 piers were installed along the 100 feet
section of wall and 2 piers were installed at each of the 14 foot returns. A 50 kip drive load was
specified per pier with a minimum factor of safety of 1.5 after the lift. Excavation to site clean-up
was completed in just four days.

25.  Mud jacking is used when a foundation is so weak that piers or pilings
cannot be installed and where concrete slabs are lifted or moved using a
complex hydraulic system.
 Small holes are drilled and polyurethane resins are injected. When the
resins mix underneath a foundation, they form a gas bubbles and expands
which results in lifting of buildings.
 After lifting, the small hole are patched with concrete.
 It is a convenient and inexpensive way to lift pool decks, slabs, driveways
and other items made of concrete that is 3 to 6 inches thick.
 Mud jacking is cheaper and can often be completed in a day or two days.

27. PROBLEM:
In the 4 years since construction, the CNIM factory, Canjiang Industrial Park,
China , the floors had subsided up to 365mm, making some areas unproductive in last
12 months.
SOLUTION:
Soil stabilisation and compaction was carried out using the deep injection
technology of expanding resins at extremely high pressures at the weak locations and
levels as detected by the penetrometer testing. Floor slabs were lifted and voids beneath
the slabs filled by foam injected directly below the slab.