PRESENTED BY ARCHANA MALLICK 7 TH SEMCIVIL INTRODUCTION T ransportation contributes to the economicindustrialsocial and cultural development of any country Transportation by road or highways is the only mode which could give maximum service to one and all ID: 562315
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Slide1
Modern GROUND IMPROVEMENT TECHNIQUES FOR HIGHWAYS
PRESENTED BY
ARCHANA MALLICK
7
TH
SEM,CIVILSlide2
INTRODUCTION
T
ransportation 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:Slide3
METHODS FOR GROUND IMPROVEMENT
1. VERTICAL DRAINS
2
. SOIL NAILING
3
. STONE COLUMNS
4
. VIBRO COMPACTION
5
. DYNAMIC COMPACTION
6
. VIBRO PIERSSlide4
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 belowSlide5
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. Slide6
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.
M
ost common application of wick drains is for accelerating the settlement rate of compressible soils.Slide7
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.)
Slide8
APPLYING SHOTCRETE
HOLES DRILLED THROUGH MACHINESSlide9
SOIL NAILINGSlide10
STONE COLUMNS
A
lso 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.Slide11
STONE COLUMNSSlide12Slide13
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.Slide14
PROCESS OF VIBRO COMPACTIONSlide15
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. Slide16
MACHINE WITH TAMPER
COMPACTION BY TAMPERSlide17
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.Slide18
BOTTOM FEED PROCESS
AGGREGATE INTRODUCED THROUGH PREDRILLED HOLESSlide19
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.Slide20
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.Slide21
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