Shallow Foundation Analysis and Design

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UNIVERSITI MALAYSIA PAHANG Department of Civil
and Environmental Engineering

• Chapter 2
• Shallow Foundation Analysis and Design

Muzamir bin Hasan, M.Eng. Lecturer
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Shallow Foundations

• Shallow foundations transfer structural loads to
  relatively small depths into the ground.
• Range from isolated foundations, each carrying
  its own column load, to elements carrying several
  load columns, walls or even all the loads for a
  given structure or building.

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ADVANTAGES OF USING SHALLOW FOUNDATION

• 1- Cost (affordable)2- Construction Procedure
  (simple) 3- Materials (mostly concrete)4- Labor
  (does not need expertise)

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Shallow Foundations
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Shallow Foundations
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Shallow Foundations
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Shallow Foundations
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Shallow Foundations
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Shallow Foundations
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Shallow Foundations
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DISADVANTAGES OF USING SHALLOW FOUNDATION

• 1- Settlement2- Limit Capacity Soil
  Structure3- Irregular ground surface (slope,
  retaining wall)4- Foundation subjected to
  pullout, torsion, moment.

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Shallow vs. Deep Foundations
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Shallow Foundations

• Usually the more economical option
• As a general rule, consider deep foundations only
  when shallow foundations do not give satisfactory
  design
• Types of Shallow foundations
• Spread footings (square, circular, rectangular)
• Combined Footings
• Continuous Footings
• Mat or Raft Foundations

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Combined/Strap Footing
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Construction Methods

• Excavation Backhoe followed by handwork
• Neat footing-no formwork used
• Formed footing

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Construction of Shallow Foundations
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Construction of Shallow Foundations
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Construction of Shallow Foundations
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Construction of Shallow Foundations
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Construction of Shallow Foundations
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Construction of Shallow Foundations
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Construction of Shallow Foundations
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Construction of Shallow Foundations
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Basic Construction Specifications and Items for
Inspection

• 3 construction requirements must be address in
  the construction specification for footings in
  soil-
• Minimum depth to base of footing
• Certain minimum distances with the respect to
  buried utilities, cavities, or other foundation
  elements
• Sequence of construction of individual footings

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Basic Construction Specifications and Items for
Inspection
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Basic Construction Specifications and Items for
Inspection
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Example 8-1

• Youre designing a square footing near the
  property line of an adjacent structure. The local
  municipality owns an easement along the property
  line for a sewer pipe with diameter equal to 0.5
  m and an invert depth of 4 m below grade. At what
  distance from the property line and at what depth
  would u consider placing your footing?

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Example 8-1
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Solution
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Basic Construction Specifications and Items for
Inspection
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Construction Inspection

• Base elevation
• Nature and type of soil at the base of the
  excavation
• Base cleaning before concrete placement
• Dimensions and cross section of footings, grade
  beams and other foundation elements
• Concrete placement
• Time for concrete placement
• Footing integrity after concrete placement

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Dewatering

• Sump pumping
• Wellpoints

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Sump Pumping

• Under CERTAIN conditions, be effective
• Pump placed inside a sump, usually partly
  backfilled with gravel to prevent the development
  of quick condition
• GW accumulates within the sump as it surfaces,
  from which it is pumped out

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Wellpoints

• Installed in series along the borders of the zone
  to be dewatered
• Effective for relatively clean sand
• Higher fines content may lead to wellpoint
  clogging

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Wellpoints