Geogrid as reinforcement Notes

 Page 1


Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
 
The Lecture Contains: 
Applications
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_1.htm [10/12/2011 11:54:41 AM]
Page 2


Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
 
The Lecture Contains: 
Applications
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_1.htm [10/12/2011 11:54:41 AM]
Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
Geogrid
Reinforcement:
 
Unpaved Roads: 
Mechanism of reinforcement
?     Increased soil strength.
?     Load spreading.
?     Membrane support via controlled rutting.
The difference in required thickness of stone base is obtained and then compared to the cost of Geogrid.
Figure 28.1
Three Mechanisms:
(1).An increased in soil subgrade strength from the non-reinforced case to the reinforced case.
 = bearing capacity pressured based on the elastic limit.
 
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_2.htm (1 of 2) [10/12/2011 11:54:42 AM]
Page 3


Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
 
The Lecture Contains: 
Applications
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_1.htm [10/12/2011 11:54:41 AM]
Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
Geogrid
Reinforcement:
 
Unpaved Roads: 
Mechanism of reinforcement
?     Increased soil strength.
?     Load spreading.
?     Membrane support via controlled rutting.
The difference in required thickness of stone base is obtained and then compared to the cost of Geogrid.
Figure 28.1
Three Mechanisms:
(1).An increased in soil subgrade strength from the non-reinforced case to the reinforced case.
 = bearing capacity pressured based on the elastic limit.
 
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_2.htm (1 of 2) [10/12/2011 11:54:42 AM]
Objectives_template
 = bearing capacity pressured based on the plastic limit.
 = undrained soil strength at the   vehicle passage
 = aggregate thickness without reinforcement
h = aggregate thickness with reinforcement.
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_2.htm (2 of 2) [10/12/2011 11:54:42 AM]
Page 4


Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
 
The Lecture Contains: 
Applications
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_1.htm [10/12/2011 11:54:41 AM]
Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
Geogrid
Reinforcement:
 
Unpaved Roads: 
Mechanism of reinforcement
?     Increased soil strength.
?     Load spreading.
?     Membrane support via controlled rutting.
The difference in required thickness of stone base is obtained and then compared to the cost of Geogrid.
Figure 28.1
Three Mechanisms:
(1).An increased in soil subgrade strength from the non-reinforced case to the reinforced case.
 = bearing capacity pressured based on the elastic limit.
 
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_2.htm (1 of 2) [10/12/2011 11:54:42 AM]
Objectives_template
 = bearing capacity pressured based on the plastic limit.
 = undrained soil strength at the   vehicle passage
 = aggregate thickness without reinforcement
h = aggregate thickness with reinforcement.
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_2.htm (2 of 2) [10/12/2011 11:54:42 AM]
Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
 
Geogrid
(2) An improved load distribution to the soil sub grade due to load spreading.
 = New angle
(3) A tensioned membrane effect, which is a function of tensile modulus and elongation of Geogrid and to 
deformed surface of the sub grade soil i.e. the rut depth.
Girood et al(1984) have developed the design chart.
 
 
Figure 28.2
In the right hand of the graph, for a standard axle load and any number of vehicle passes from 10 to 
10000, a thickness of non-reinforcement stone base  can be obtained knowing the soil sub grade 
strength.
Knowing this value of ,carried to the left side of the figure, where it intersect any arc of curve then you 
get R , h could be found out. 
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_3.htm (1 of 2) [10/12/2011 11:54:42 AM]
Page 5


Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
 
The Lecture Contains: 
Applications
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_1.htm [10/12/2011 11:54:41 AM]
Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
Geogrid
Reinforcement:
 
Unpaved Roads: 
Mechanism of reinforcement
?     Increased soil strength.
?     Load spreading.
?     Membrane support via controlled rutting.
The difference in required thickness of stone base is obtained and then compared to the cost of Geogrid.
Figure 28.1
Three Mechanisms:
(1).An increased in soil subgrade strength from the non-reinforced case to the reinforced case.
 = bearing capacity pressured based on the elastic limit.
 
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_2.htm (1 of 2) [10/12/2011 11:54:42 AM]
Objectives_template
 = bearing capacity pressured based on the plastic limit.
 = undrained soil strength at the   vehicle passage
 = aggregate thickness without reinforcement
h = aggregate thickness with reinforcement.
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_2.htm (2 of 2) [10/12/2011 11:54:42 AM]
Objectives_template
 Module 10:Design methods of Geogrids, Geonets and geomembranes 
 Lecture 28:Geogrid as reinforcement 
 
 
Geogrid
(2) An improved load distribution to the soil sub grade due to load spreading.
 = New angle
(3) A tensioned membrane effect, which is a function of tensile modulus and elongation of Geogrid and to 
deformed surface of the sub grade soil i.e. the rut depth.
Girood et al(1984) have developed the design chart.
 
 
Figure 28.2
In the right hand of the graph, for a standard axle load and any number of vehicle passes from 10 to 
10000, a thickness of non-reinforcement stone base  can be obtained knowing the soil sub grade 
strength.
Knowing this value of ,carried to the left side of the figure, where it intersect any arc of curve then you 
get R , h could be found out. 
 
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_3.htm (1 of 2) [10/12/2011 11:54:42 AM]
Objectives_template
  
 
 
 
 
 
 
 
 
file:///D|/Dr.patra/ground_improvement_techniques/lecture28/28_3.htm (2 of 2) [10/12/2011 11:54:42 AM]