Modern GROUND IMPROVEMENT TECHNIQUES FOR HIGHWAYS

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Modern GROUND IMPROVEMENT TECHNIQUES FOR
HIGHWAYS

• PRESENTED BY
• ARCHANA MALLICK
• 7TH SEM,CIVIL

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INTRODUCTION

• Transportation contributes to the
  economic,industrial,social and cultural
  development of any country.
• Transportation by road or highways is the only
  mode which could give maximum service to one and
  all.
• When the soil on a project site cannot support
  the loads, ground improvement to increase
  strength, reduce compressibility, and enhance
  performance under applied loadings may be
  required.
• The field of ground improvement techniques has
  been recognized as an important and rapidly
  expanding one.
• Various methods are discussed below

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METHODS FOR GROUND IMPROVEMENT

• 1. VERTICAL DRAINS
• 2. SOIL NAILING
• 3. STONE COLUMNS
• 4. VIBRO COMPACTION
• 5. DYNAMIC COMPACTION
• 6. VIBRO PIERS

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VERTICAL DRAINS

• These consist of a column of pervious material
  placed in cylindrical vertical holes at
  sufficiently close spaces.
• All drains should be connected at the ground
  surface to a drainage blanket.
• Vertical drains accelerate consolidation by
  facilitating drainage of pore water.
• Vertical drains are laid out in rows, staggered,
  or aligned to form patterns of equilateral
  triangles or squares.
• Two types of drains are discussed below

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SAND DRAINS

• A sand drain is a simple process, employing a
  column of at least 10 inches in width augered
  into ground to be surcharged and consolidated.
• The column is then filled with sand and
  connected to a free-draining blanket of granular
  soil.

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WICK DRAINS

• A wick drain is usually about, 4 inches wide,
  1/8-inch thick which acts as a high-permeability
  conduit for water to flow out of the soil and to
  the surface.
• Most common application of wick drains is for
  accelerating the settlement rate of compressible
  soils.

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SOIL NAILING

• This ground reinforcement process uses steel
  tendons which are drilled and grouted into the
  soil to create a composite mass.
• A shotcrete facing is typically applied.
• Soil Nailing is an in situ technique for
  reinforcing, stabilizing and retaining
  excavations and deep cuts.
• Soil nailing is not practical in
• Soft, plastic clays
• Organics/Peat
• Fills (rubble, cinder, ash, etc.)

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APPLYING SHOTCRETE

• HOLES DRILLED THROUGH MACHINES

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• SOIL NAILING

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STONE COLUMNS

• Also known as vibro-replacement or
  vibro-displacement, is a ground improvement
  process where vertical columns of compacted
  aggregate are formed through the soils to be
  improved.
• The vibrator first penetrates to the required
  depth by vibration and air or water jetting or by
  vibration alone.
• Gravel is then added at the tip of the vibrator
  and progressive raising and repenetration of the
  vibrator results in the gravel being pushed into
  the surrounding soil.
• The soil-column matrix results in an overall mass
  having a high shear strength and a low
  compressibility.

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STONE COLUMNS
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VIBRO COMPACTION

• It is a ground improvement process for densifying
  loose sands to create stable foundation soils.
• The action of the vibrator, usually accompanied
  by water jetting, reduces the inter-granular
  forces between the soil particles, allowing them
  to move into a denser configuration, typically
  achieving a relative density of 70 to 85 percent.
• Compaction is achieved above and below the water
  table.

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• PROCESS OF VIBRO COMPACTION

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DYNAMIC COMPACTION

• Dynamic Compaction is the dropping of heavy
  weights on the ground surface to densify soils at
  depth.
• It involves the repeated dropping of large steel
  tampers by means of crawler cranes.
• Tampers typically range from 6 to 20 tons and
  are dropped from heights of about 40 to 80 feet.

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• MACHINE WITH TAMPER

• COMPACTION BY TAMPER

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VIBRO PIERS

• Vibro Piers, also known as aggregate piers, are
  typically installed to intermediate depths of 5
  to 20 feet for the support of new loads.
• Vibro Piers are quick to install and very
  effective at reinforcing the surrounding soil.
• Typical Vibro Pier construction begins with
  pre-drilling a full-depth hole with a diameter
  that is equal to the final pier design diameter.
• For soils in which the pre-drilled hole will not
  stay open, the bottom feed process can be used to
  avoid the need for casing.

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• AGGREGATE INTRODUCED THROUGH PREDRILLED HOLES

• BOTTOM FEED PROCESS

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CONCLUSION

• Though the term Ground Improvement has been
  familiar to Civil Engineers, the design approach
  is still empirical, mostly based on past
  experience.
• The Importance of Ground Improvement is
  immeasurable. Ground stability is a
  vital part of any construction project.
• Method adopted to be applied on the field should
  be according to site condition and economical.
• Application of Ground Improvement Techniques is
  not only cheaper but also reduce the
  construction time significantly.
• Ground improvement technique also plays a vital
  role in the development of our mother land by
  2020.

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REFERENCES

• K.R.Arora, (2005)"Soil Mechanics and Foundation
  Engineering", Standard Publishers Distributors,
  Delhi.
• www.haywardbaker.com .
• TerraSystems(Geotechnical Contracting Firm) .
• www.google.com
• Rembco Geotechnical Contractors Inc.

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THANK YOU