Deep Foundations and Retaining Structures
Introduction – Chapter 1
General Requirements for Footing Design
1. A site investigation is required to determine the
chemical and physical properties of the soil.
2. Determine the magnitude and distribution of
loads form the superstructure.
3. Establish the criteria and the tolerance for the
total and differential settlements of the structure.
General Requirements for Footing Design
4. Determine the most suitable and economic type
of foundation.
5. Determine the depth of the footings below the
ground level and the method of excavation.
6. Establish the allowable bearing pressure to be
used in design.
General Requirements for Footing Design
7. Determine the pressure distribution beneath the
footing based on its width
8. Perform a settlement analysis.
Recommendation of Soils Conditions and appropriate
Foundation Types
Soil Condition
Appropriate Foundation Type and Location
Design Comments
Recommendation of Soils Conditions and appropriate
Foundation Types (Cont.)
Soil Condition
Appropriate Foundation Type and Location
Design Comments
Recommendation of Soils Conditions and appropriate
Foundation Types (Cont.)
Soil Condition
Appropriate Foundation Type and Location
Design Comments
Recommendation of Soils Conditions and appropriate
Foundation Types (Cont.)
Soil Condition
Appropriate Foundation Type and Location
Design Comments
Recommendation of Soils Conditions and appropriate
Foundation Types (Cont.)
Soil Condition
Appropriate Foundation Type and Location
Design Comments
Rare Foundation Failure
of a Building in Shanghai, China
Sequence of the failure of the building
(a) First, the apartment building was constructed
(b) Then the plan called for an underground garage to
be dug out. The excavated soil was piled up on the
other side of the building
(c) Heavy rains resulted in water
seeping into the ground
(d) The building began to shift and the concrete piles snapped
due to the uneven lateral pressures
(e) The building started to tilt
(f) Final failure of the building
Some effects of liquefaction during the 1964 Niigata earthquake
Foundation Weakening Due to Soil Liquefaction in Adapazari, Turkey ‐ Source: USGS
The effect of liquefaction in Christchurch, New Zealand, during the Mw 6.3 February 2011
Christchurch earthquake
Quicksand tank
(a) Under an upward gradient,
the sand mass is easily stirred
with a mater stick
(b) Gradient is downward;
sand is able to support a static
load
(c) After a shock load is applied to the side of the tank, the sand
mass liquefies and momentarily loses all bearing capacity.
Liquefaction
The sudden, large decrease of shear strength of
cohesion‐less soil caused by collapse of the soil
structure, produced by shock – or earthquake
induced shear strain, associated with a sudden but
temporary increase of pore water pressure.
Liquefaction cause the cohesion‐less soil behave as
a fluid.
Relationship between grading and liquefaction
potential.
Within the scope of other Geotechnical Engineering
Unit
Within the scope of this unit