Unit I_ Soil Compaction methods - Moisture Density Relation
- 2. Compaction The process of bringing the soil particles closer to a dense state by mechanical means. The voids are reduced by expulsion of air and the soil particles are packed together, thereby increasing its unit weight. There is no substantial change in the volume of water in soil during compaction. Compaction is done to improve the Engineering properties of soil such as increase of shear, increase the bearing strength, reduce the compressibility of soil, change the soil properties like shrinkage, frost susceptibility and permeability of soils.
- 3. Uses of soil In the following cases, soil is used as fill: Backfill of excavation i.e. foundation To develop made up soils for the building. As sub grade, sub base, for roads railways and airfields. As an earthen dam. To develop site in a difficult terrain, where substantial cutting and filling is required.
- 4. Objectives of Compaction Increase the shear strength. Increased bearing capacity for foundation support. Reduce compressibility and smaller settlement of buildings and lesser deformation of earth structures. Reduce permeability, leading to less seepage of water. Improve stability and lower damage due to frost action. Heavy/highway vs. building foundation compaction operations. To reduce the degree of shrinkage and formation of cracks on drying.
- 5. Soil Compaction Soil Compaction can be achieved either by static or dynamic loading: 1- Smooth-wheel rollers 2- Sheep foot rollers 3- Rubber-tired rollers 4- Vibratory Rollers 5- Vibro flotation
- 6. Factors affecting Compaction Five factors affecting compaction 1. Physical & chemical properties 2. Moisture content 3. Method of compaction 4. Amount of compactive effort
- 8. Effect of Energy on Soil Compaction Increasing compaction energy Lower MC and higher dry density
Editor's Notes
- #1: Most soil classifications employ very simple index-type tests to obtain the characteristics of the soil needed to place it in a given group. Clearly a soil classification loses its value if the index tests become more complicated than the test to measure directly the fundamental property needed. The most commonly used characteristics are particle size and plasticity. Empirical correlations between index properties and fundamental soil behavior have many large deviations. The particle size distribution and the Atterberg limits are useful index tests inherently involves disturbance of the soil, they may not give a good indication of the behavior of the in situ, undisturbed soil.
- #2: Most soil classifications employ very simple index-type tests to obtain the characteristics of the soil needed to place it in a given group. Clearly a soil classification loses its value if the index tests become more complicated than the test to measure directly the fundamental property needed. The most commonly used characteristics are particle size and plasticity. Empirical correlations between index properties and fundamental soil behavior have many large deviations. The particle size distribution and the Atterberg limits are useful index tests inherently involves disturbance of the soil, they may not give a good indication of the behavior of the in situ, undisturbed soil.