Course
Year
: S0892 - Ground Improvement Method
: 2010
UNIQUE SOILS
(BASIC PRINCIPLE & IMPROVEMENT METHOD)
Session 11
COURSE 4
Content:
• Expansive Soils
• Organic Soil, Peat
• Collapsible Soil
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EXPANSIVE SOILS
expansive soils are
types of soil that shrink
or swell as the moisture
content decreases or
increases. These soils
typically contain clay
minerals that attract and
absorb water.
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EXPANSIVE SOILS – PROBLEMS
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EXPANSIVE SOILS – SOLUTION
• Static/Mechanical Stabilization
– Maintain the water level elevation
– Applying load on top to retain the swelling pressure of
expansive soils
• Chemical Stabilization
Mixing chemical admixture such as:
– Cement
– Lime
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EXPANSIVE SOILS – SOLUTIONS
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EXPANSIVE SOILS – SOLUTIONS
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EXPANSIVE SOILS – SOLUTIONS
An alternative method for handling highly expansive
soils using mass grading is to cover them with 15 feet
of select non-expansive fill
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EXPANSIVE SOILS – SOLUTIONS
DRILLED PIERS AND
GRADE BEAM
Drilled piers and grade beam
foundation systems must extend
below the zone of seasonal
moisture fluctuation, holding the
structure down, when lightly
loaded elements are subjected to
moisture absorption and heave
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EXPANSIVE SOILS – SOLUTIONS
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EXPANSIVE SOILS – SOLUTIONS
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EXPANSIVE SOILS – SOLUTIONS
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ORGANIC SOILS (PEAT)
• Peat is an organic soil which
consists more than 70% of organic
matters. Peat deposits are found
where conditions are favorable for
their formation.
• Peat poses serious problems in
construction due to its long-term
consolidation settlements even
when subjected to a moderate load.
• Peat is considered unsuitable for
supporting foundations in its natural
state.
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ORGANIC SOILS (PEAT)
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ORGANIC SOILS (PEAT) – PROBLEMS
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ORGANIC SOILS (PEAT) – SOLUTION
The modification of soil properties to improved states of load-bearing capacity
may be done in a number of ways including the following (Bowels, 1988):
• Compaction. Usually the most economical method.
• Preloading. Primarily to reduce future settlement but may also be used to
increase shear strength.
• Drainage. Used to speed up settlement under preloading but may also
increase shear strength.
• Densification using vibratory equipment. Particularly in silty sand and gravelly
sand with a relative density below 50 to 60%.
• Grouting. Both to reduce voids and to stiffen soil.
• Chemical stabilization. To stiffen soil.
• Use of geotextiles. Primarily as reinforcement but sometimes in other
beneficial modes.
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ORGANIC SOILS (PEAT) – SOLUTION
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ORGANIC SOILS (PEAT) – SOLUTION
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ORGANIC SOILS (PEAT) – SOLUTION
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COLLAPSIBLE SOILs
• Soils which are subjected to
compressive deformation due
to wetting (saturation collapse)
under natural conditions
• Collapsible soils will settle
without any additional applied
pressure when sufficient water
becomes available to the soil.
Water weakens or destroys
bonding material between
particles that can severely
reduce the bearing capacity of
the original soil.
• The collapse potential of
these soils must bedetermined
for consideration in the
foundation design.
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COLLAPSIBLE SOILS
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COLLAPSIBLE SOIL – SOLUTION
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REINFORCEMENT USING GEOSYNTHETIC
COLLAPSIBLE SOIL – SOLUTION
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