Classification of Ground Modification Techniques - Self Help Learning PDF Download

 Page 1


NPTEL Online - IIT Bombay
 
 
Course Name Ground Improvement 
                          Techniques  
 
 
Department   Civil Engineering 
                          IIT Kanpur  
 
Instructor       Dr. N.R. Patra 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/main.html [10/11/2011 12:31:05 PM]
Page 2


NPTEL Online - IIT Bombay
 
 
Course Name Ground Improvement 
                          Techniques  
 
 
Department   Civil Engineering 
                          IIT Kanpur  
 
Instructor       Dr. N.R. Patra 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/main.html [10/11/2011 12:31:05 PM]
Objectives_template
 Module 1:Introduction 
 Lecture 1:Classification of Ground modification Techniques 
 
 
The Lecture Contains: 
Introduction
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/1_1.htm [10/11/2011 12:31:06 PM]
Page 3


NPTEL Online - IIT Bombay
 
 
Course Name Ground Improvement 
                          Techniques  
 
 
Department   Civil Engineering 
                          IIT Kanpur  
 
Instructor       Dr. N.R. Patra 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/main.html [10/11/2011 12:31:05 PM]
Objectives_template
 Module 1:Introduction 
 Lecture 1:Classification of Ground modification Techniques 
 
 
The Lecture Contains: 
Introduction
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/1_1.htm [10/11/2011 12:31:06 PM]
Objectives_template
 Module 1:Introduction 
 Lecture 1:Classification of Ground modification Techniques 
 
 
Introduction 
Need for Engineering ground Improvement 
When a project encounters difficult foundation conditions, possible alternate solutions are:
?     Avoid the particular site
?     Design the planned structure accordingly.
      Use a soft foundation supported by piles, design a very stiff structure which is not damaged by settlements
?     Remove and replace unsuitable soils.
?     Attempt to modify the existing ground.
  Classification of Ground modification Techniques:   
       4 Groups of Ground Improvement techniques 
  Mechanical Modification: 
 Soil density is increased by the application of mechanical force, including compaction of surface layers  by static vibratory such 
as compact roller and plate vibrators.
  Hydraulic Modification:
?     Free pore water is forced out of soil via drains or wells.
?     Course grained soils; it is achieved by lowering the ground water level through pumping from boreholes, or trenches.
?     In fine grained soils the long term application of external loads (preloading) or electrical forces (electrometic stabilization)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/1_2.htm [10/11/2011 12:31:06 PM]
Page 4


NPTEL Online - IIT Bombay
 
 
Course Name Ground Improvement 
                          Techniques  
 
 
Department   Civil Engineering 
                          IIT Kanpur  
 
Instructor       Dr. N.R. Patra 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/main.html [10/11/2011 12:31:05 PM]
Objectives_template
 Module 1:Introduction 
 Lecture 1:Classification of Ground modification Techniques 
 
 
The Lecture Contains: 
Introduction
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/1_1.htm [10/11/2011 12:31:06 PM]
Objectives_template
 Module 1:Introduction 
 Lecture 1:Classification of Ground modification Techniques 
 
 
Introduction 
Need for Engineering ground Improvement 
When a project encounters difficult foundation conditions, possible alternate solutions are:
?     Avoid the particular site
?     Design the planned structure accordingly.
      Use a soft foundation supported by piles, design a very stiff structure which is not damaged by settlements
?     Remove and replace unsuitable soils.
?     Attempt to modify the existing ground.
  Classification of Ground modification Techniques:   
       4 Groups of Ground Improvement techniques 
  Mechanical Modification: 
 Soil density is increased by the application of mechanical force, including compaction of surface layers  by static vibratory such 
as compact roller and plate vibrators.
  Hydraulic Modification:
?     Free pore water is forced out of soil via drains or wells.
?     Course grained soils; it is achieved by lowering the ground water level through pumping from boreholes, or trenches.
?     In fine grained soils the long term application of external loads (preloading) or electrical forces (electrometic stabilization)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/1_2.htm [10/11/2011 12:31:06 PM]
Objectives_template
 Module 1:Introduction 
 Lecture 1:Classification of Ground modification Techniques 
 
 
Physical and chemical modification: 
Stabilization by physical mixing adhesives with surface layers or columns of soil. 
Adhesive includes natural soils industrial byproducts or waste. Materials or cementations or other chemicals which react with 
each other and/or the ground. 
When adhesives are injected via boreholes under pressure into voids within the ground or between it and a structure the process 
is called grouting.
Soil stabilization by heating and by freezing the ground is considered thermal methods of modifications.
Modification by inclusions and confinement: 
Reinforcement by fibers, strips bars meshes   and fabrics imparts tensile strength to a constructed soil mass.
In-situ reinforcement is achieved by nails and anchors. Stable earth retaining stucture can also be formed by confining soil with 
concrete, Steel, or fabric elements 
Suitability, Feasibility and Desirability 
The choice of a method of ground improvement for a particular object will depend on the following factors.
?     Type and degree of improvement required 
?     Type of soil , geological structure, seepage conditions 
?     cost                                                                                                                                   
?     Availability of equipment and materials and the quality of work required 
?     Construction time available 
?     Possible damage to adjacent structures or pollution of ground water resources
?     Durability of material involved ( as related to the expected life of structure for a given environmental and stress conditions)
?     Toxicity or corrosivity of any chemical additives .
?     Reliability of method of analysis and design.
?     Feasibility of construction control and performance measurements
If soil is moist, freezing is applicable to all type of soil.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture1/1_3.htm [10/11/2011 12:31:07 PM]