Lecture

Topics: Waste management, Geotechnical engineering, Waste Pages: 5 (546 words) Published: September 14, 2013
Lecture 3

NPTEL Course

GROUND IMPROVEMENT
Prof. G L Sivakumar Babu Department of Civil Engineering Indian Institute of Science Bangalore 560012 Email: gls@civil.iisc.ernet.in

Module I



Need for Ground Improvement Classification of ground modification techniques



Emerging trends in ground Improvement

Recap: Classification of Ground Improvement techniques Methods and techniques of Ground Improvement Factors affecting the selection of techniques

Need for Soil Improvement

Soft Clay

Liquefaction and sinkhole formation

Methods for Soil Improvement
Ground Reinforcement • Stone Columns • Soil Nails • Micropiles • Jet Grouting • Ground Anchors • Geosynthetics • Fibers • Lime Columns • Vibro-Concrete Column • Mechanically Stabilized Earth • Biotechnical Ground Improvement Ground Treatment

• Surface • Soil Cement Compaction • Lime Admixtures • Drainage/Surcharge • Flyash • Electro-osmosis • Dewatering • Compaction • Heating/Freezing grouting • Vitrification • Blasting • Dynamic Compaction

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 soilcrete columns

Stone columns

Nailing and Reinforced soil

Geosynthetic products

Fibers and reinforced earth

Effect of fibers on strength response
1400 1200 1000 D eviator stress(kPa) 800 600 400 200 0 0 5 10 Strain(%) 15 20 25 Red soil fl =15 mm fd = 0.25mm σ3 =50 kPa 0% 0.50% 1.00% 1.25% 1.50% 2.00% 2.50%

Effect of fibers on compressibility
0.7
red soil fl = 10mm fd = 0.25mm

0.6

0% 0.50% 1.0% 1.50% 2.00% 2.5%

void ratio

0.5

0.4

0.3 1 10 log p(kPa) 100 1000

Effect of fibers on swell response
7.0 6.0 5.0 Swell (%) 4.0 3.0 2.0 1.0 0.0 1 10 100 Time (minutes) 1000 10000 Black cotton soil fl =15mm fd = 0.25mm 0% 0.50% 1.00% 1.50%

Effect of fibers on piping resistance
0.25
Red soil fl = 50 mm

Seepage velocity (cm/sec)

0.20

0.15

0.10 0% 0.25% 0.50% 0.75% 1.00% 0.0 0.5 1.0 1.5 2.0 Hydraulic gradient 2.5 3.0 3.5

0.05

0.00

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.

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