presented by:
ARCHANA MALLICK

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Modern GROUND IMPROVEMENT TECHNIQUES FOR HIGHWAYS
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:
METHODS FOR GROUND IMPROVEMENT
1. VERTICAL DRAINS
2. SOIL NAILING
3. STONE COLUMNS
4. VIBRO COMPACTION
5. DYNAMIC COMPACTION
6. VIBRO PIERS
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
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.
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.
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:
1. Soft, plastic clays
2. Organics/Peat
3. Fills (rubble, cinder, ash, etc.)
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.
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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