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GROUND IMPROVEMENT
NPTEL Course
Prof. G L Sivakumar BabuDepartment of Civil EngineeringIndian Institute of ScienceBangalore 560012Email: [email protected]
Lecture 3
Module I
Need for Ground Improvement Classification of ground modification
techniques Emerging trends in ground Improvement
Recap:Classification of Ground Improvement techniquesMethods and techniques of Ground ImprovementFactors affecting the selection of techniques
Need for Soil Improvement
Soft Clay Liquefaction and sinkhole formation
Methods for Soil ImprovementGround
ReinforcementGround
ImprovementGround
Treatment
• Stone Columns• Soil Nails• Micropiles• Jet Grouting• Ground Anchors• Geosynthetics• Fibers • Lime Columns• Vibro-Concrete
Column• Mechanically
Stabilized Earth• Biotechnical
• Surface Compaction
• Drainage/Surcharge• Electro-osmosis• Compaction
grouting• Blasting• Dynamic
Compaction
• Soil Cement• Lime Admixtures• Flyash• Dewatering• Heating/Freezing• Vitrification
Benefits/Objectives of ground improvement techniques
Increase of strength Reduce distortion under stress (Increases
stress-strain modulus) Reduce compressibility (volume decreases
due to a reduction in air voids or water content under loads)
Continued :
Prevent detrimental physical or chemical changes due to environmental conditions (freezing / thawing, wetting / drying)
Reduce susceptibility to liquefaction Reduce natural variability of borrow
materials and foundation soils
Jet grouted soilcretecolumns
Stone columns
Nailing and Reinforced soil
Geosynthetic products
Fibers and reinforced earth
Effect of fibers on strength response
0
200
400
600
800
1000
1200
1400
0 5 10 15 20 25Strain(%)
Dev
iato
r stre
ss(k
Pa)
0%0.50%1.00%1.25%1.50%2.00%2.50%
Red soilfl =15 mmfd = 0.25mmσ3 =50 kPa
Effect of fibers on compressibility
0.3
0.4
0.5
0.6
0.7
1 10 100 1000log p(kPa)
void
ratio
0%0.50%1.0%1.50%2.00%2.5%
red soilfl = 10mmfd = 0.25mm
Effect of fibers on swell response
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
1 10 100 1000 10000Time (minutes)
Swel
l (%
)
0%0.50%1.00%1.50%
Black cotton soilfl =15mmfd = 0.25mm
Effect of fibers on piping resistance
0.00
0.05
0.10
0.15
0.20
0.25
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5Hydraulic gradient
Seep
age
velo
city
(cm
/sec
)
0%0.25%0.50%0.75%1.00%
Red soilfl = 50 mm
Trends Today
Environmental Geotechnics and solid waste management using ground improvement techniques
Containment and constructive use of waste materials
Low-cost technologies with soil and additives
Geosynthetics Biotechnical stabilization
Catalysts and accelerators
Development of new machinery, particularly for deep compaction
Availability of new construction materials such as geofoams, geocomposites
Emergence of better guidelines for determining the suitability of specific techniques for certain types of soils and site conditions.
Better understanding of the geotechnical processes involved and appreciation of the significance of the construction sequence.
Refinement of methods of analysis and computer modeling techniques
Likely Trends Tomorrow Microbes to stabilize or remediate soils, Nanotechnology to modify the behavior of clay, Nano-sensors and MEMS to characterize and
monitor the behavior of geomaterials and geosystems,
Remote sensing and noninvasive ground-based sensing techniques, and
Next-generation geologic data models to bridge sensing, computation, and real-time simulation of behavior for adaptive management purposes and geophysics for urban infrastructure detection.
