introduction to ground improvement, types, ant its techniques by different methods (few of them are explained).

2. Seminar topic:
Ground Improvement
& Its Techniques
Submitted by:
Junaid Bashir
06-CE-2012
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3.  Definition:
 The term ground improvement refers to the modification to the engineering
properties of soil that are carried out at a site where the soil in its natural
state does not possess properties that are acceptable to us for the proposed
Civil Engineering activity.
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4.  Why ground improvement is
necessary?
 Scarcity of useful land.
 Engineer often ask for the following improvement in the soil.
1) To increase the bearing capacity.
2) A reduction in the amount of settlement and in the time in which it occurs.
3) To increase or decrease permeability.
4) To reduce compressibility.
5) stability
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5.  Types of ground improvement:
 Deep Dynamic compaction.
 stone columns.
 Sand compaction piles.
 Injection of suitable grouts.
 Preloading of soil.
 Soil Nailing.
 Use of Admixtures.
 Removal and replacement.
 Miscellaneous
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6.  DynamicCompaction:
 There are two types of dynamic compaction for deeper layers of soils:
i. Vibroflotation.
ii. Dropping of heavy weight.
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7.  Vibroflotation:
 Vibroflotation is a technique
for in situ densification of
cohesionless soils. It was
developed in Germany in the
1930s.
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8.  Vibroflotation-Procedure:
• Stage1: The jet at the bottom of the Vibroflot is turned
on and lowered into the ground
• Stage2: The water jet creates a quick condition in the
soil. It allows the vibrating unit to sink into the ground
• Stage 3: Granular material is poured from the top of
the hole. The water from the lower jet is transferred
to the jet at the top of the vibrating unit. This water
carries the granular material down the hole
• Stage 4: The vibrating unit is gradually raised in about
0.3m lifts and held vibrating for about 30 seconds at
each lift. This process compacts the soil to the desired
unit weight.
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9.  Dropping of heavy weight:
 Compacting cohesionless and cohesive soils.
 It involves the repeated dropping of a large weight (02 to 50 tonnes) falling
freely from a height of 07 to 35 metres.
 This technique can effectively compact the ground down to a depth of a few
metres.
 Not suitable for small sites or sites where vibration, impact etc. can affect
adjacent buildings or building service in the ground
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10.  Contd. :
by heavy weight:
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11.  stone columns:
 Particularly applicable for soft, inorganic,
cohesive soils.
 Generally inserted on a volume displacement
basis.
 Stone columns can be installed by
vibroflotation using stone as backfill material.
 Size of the stone ranges from 06-40 mm,
columns are spaced about 1.2 -03m.
 Stone columns are not effective for thick
deposits of organic clays and silts.
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12.  Soil Nailing:
 Soil nailing is a method of
construction that reinforces and
strengthens the existing ground by
installing closely spaced steel bars
“nails,” into a slope or existing ground.
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13.  Soil Nailing Procedure:
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14.  Effect on the Ground:
 Change of state;
i.e. the same ground but made stronger, stiffer, denser, more durable
 Change of nature;
i.e. the ground becomes a different material by inclusion of other materials
 Change of response;
i.e. through the incorporation of other materials, the ground becomes a
composite material with enhanced load-carrying or deformation characteristics.
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15.  Selection/Choice of method:
It depends upon :
 Availability of resources.
 Suitability.
 Nature of soil.
 Time.
 Environmental conditions.
 Economy.
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16.  Conclusion:
 Ground Improvement techniques forms technically sound and cost effective
solution where the sub soils are weak and needs to be treated to enable the
intended construction.
 Its applicability has been proven for a wide range of structures such as
roads, runways, ports, power plants, railways, dams, slope stabilisation,
excavations, tunnelling and other infrastructure facilities.
 These techniques have been used all over the world for a wide range of
soils starting from loose sands, silts, marine clays to weak rocks.
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