Ground Improvement, Civil Engineering Notes - Civil Engineering (CE)

 Page 1


GROUND 
IMPROVEMENT 
NPTEL Course 
Prof. G L Sivakumar Babu
Department of Civil Engineering
Indian Institute of Science
Bangalore 560012
Email: gls@civil.iisc.ernet.in
Lecture  9
Page 2


GROUND 
IMPROVEMENT 
NPTEL Course 
Prof. G L Sivakumar Babu
Department of Civil Engineering
Indian Institute of Science
Bangalore 560012
Email: gls@civil.iisc.ernet.in
Lecture  9
Failure Mechanisms of Stone Columns 
suggested in IS code 
Fig1(a): Failure Mechanism of Single Stone Column 
in a Homogenous Soft Layer.
Page 3


GROUND 
IMPROVEMENT 
NPTEL Course 
Prof. G L Sivakumar Babu
Department of Civil Engineering
Indian Institute of Science
Bangalore 560012
Email: gls@civil.iisc.ernet.in
Lecture  9
Failure Mechanisms of Stone Columns 
suggested in IS code 
Fig1(a): Failure Mechanism of Single Stone Column 
in a Homogenous Soft Layer.
Fig1(b): Failure Mechanism of Single Stone Column in a 
Non-Homogenous Soft Layer.
Page 4


GROUND 
IMPROVEMENT 
NPTEL Course 
Prof. G L Sivakumar Babu
Department of Civil Engineering
Indian Institute of Science
Bangalore 560012
Email: gls@civil.iisc.ernet.in
Lecture  9
Failure Mechanisms of Stone Columns 
suggested in IS code 
Fig1(a): Failure Mechanism of Single Stone Column 
in a Homogenous Soft Layer.
Fig1(b): Failure Mechanism of Single Stone Column in a 
Non-Homogenous Soft Layer.
Type of loading:
Fig1(c): Different types of 
loadings applied on Stone 
Columns. 
• In the case as 
shown in the fig1(b). 
where the loaded 
area is more than 
that of Stone columns 
experiences less 
bulging leading to 
ultimate load bearing 
capacity and reduced 
settlements since the 
load is carried by 
both soil and the 
stone columns. 
Page 5


GROUND 
IMPROVEMENT 
NPTEL Course 
Prof. G L Sivakumar Babu
Department of Civil Engineering
Indian Institute of Science
Bangalore 560012
Email: gls@civil.iisc.ernet.in
Lecture  9
Failure Mechanisms of Stone Columns 
suggested in IS code 
Fig1(a): Failure Mechanism of Single Stone Column 
in a Homogenous Soft Layer.
Fig1(b): Failure Mechanism of Single Stone Column in a 
Non-Homogenous Soft Layer.
Type of loading:
Fig1(c): Different types of 
loadings applied on Stone 
Columns. 
• In the case as 
shown in the fig1(b). 
where the loaded 
area is more than 
that of Stone columns 
experiences less 
bulging leading to 
ultimate load bearing 
capacity and reduced 
settlements since the 
load is carried by 
both soil and the 
stone columns. 
Load Tests:
? From the Load test we can determine the ultimate load 
bearing capacity and settlement of  single column with 
reasonable accuracy.
? A good experience with foundations on similar 
structures & calculations on the basis of principals of 
soil mechanics shall be made before final design.
Factor of Safety:
• The minimum Factor of safety against ultimate 
load capacity of column obtained from load test 
shall be 2.5.