soil compaction
CE 353 Geotechnical Engineering
Dr M. Touahmia
6
Soil Compaction
Lecture Outline:
1.
2.
3.
4.
5.
6.
7.
General Principles
Standard Proctor Test
Factors Affecting Compaction
Modified Proctor Test
Field Compaction
Measurement of Field Compaction
Special Compaction Techniques
Textbook: Braja M. Das, "Principles of Geotechnical Engineering", 7th E. (Chapter 6).
1
General Principles
What is compaction?
• Many types of earth construction, such as roads, railways, embankments, retaining walls, earth dams, and airport, require man-placed soils, or fills.
These soils are loose (weak) and must be compacted to increase their strength characteristics.
• Soil compaction is defined as the method of mechanically increasing the density of soil by reducing volume of air.
2
General Principles
• The densification is accomplished by pressing the soil particles together into a close state of contact with air being expelled from the soil mass in the process, thereby increasing its unit weight.
• The degree of compaction is measured in terms of the dry unit weight (γd).
• For a given water content (w), the maximum degree of compaction that can be achieved is when all of the air voids have been removed.
• The dry unit weight correlates with the degree of packing of the soil grains:
G
1 e s w
d
• The smaller the void ratio (e) will be, the higher the dry unit weight (γd) will be. 3
General Principles
Objectives of Compaction:
•
1.
2.
3.
4.
Compaction is done to improve the Engineering properties of soil such as:
Increasing the shear strength of soil (i.e., larger loads can be applied).
Decreasing future settlements.
Reducing the compressibility of soil.
Decreasing permeability.
Affecting Factors
• There are 4 control factors affecting the extent of compaction:
1.
2.
3.
4.
Compaction effort.
Soil type and gradation.
Moisture content.
Dry unit weight (dry density).
4
Dr M. Touahmia
6
Soil Compaction
Lecture Outline:
1.
2.
3.
4.
5.
6.
7.
General Principles
Standard Proctor Test
Factors Affecting Compaction
Modified Proctor Test
Field Compaction
Measurement of Field Compaction
Special Compaction Techniques
Textbook: Braja M. Das, "Principles of Geotechnical Engineering", 7th E. (Chapter 6).
1
General Principles
What is compaction?
• Many types of earth construction, such as roads, railways, embankments, retaining walls, earth dams, and airport, require man-placed soils, or fills.
These soils are loose (weak) and must be compacted to increase their strength characteristics.
• Soil compaction is defined as the method of mechanically increasing the density of soil by reducing volume of air.
2
General Principles
• The densification is accomplished by pressing the soil particles together into a close state of contact with air being expelled from the soil mass in the process, thereby increasing its unit weight.
• The degree of compaction is measured in terms of the dry unit weight (γd).
• For a given water content (w), the maximum degree of compaction that can be achieved is when all of the air voids have been removed.
• The dry unit weight correlates with the degree of packing of the soil grains:
G
1 e s w
d
• The smaller the void ratio (e) will be, the higher the dry unit weight (γd) will be. 3
General Principles
Objectives of Compaction:
•
1.
2.
3.
4.
Compaction is done to improve the Engineering properties of soil such as:
Increasing the shear strength of soil (i.e., larger loads can be applied).
Decreasing future settlements.
Reducing the compressibility of soil.
Decreasing permeability.
Affecting Factors
• There are 4 control factors affecting the extent of compaction:
1.
2.
3.
4.
Compaction effort.
Soil type and gradation.
Moisture content.
Dry unit weight (dry density).
4