As suggested by Lars Forssblad (1981), the three main actions of compaction are static pressure, impact force and vibration. Different compactors contain one or more modes of these actions. For example, vibratory tampers perform mainly by the principle of impact while vibratory rollers work with principle of static pressure and vibration.
For sandy soils, vibration is adequate for normal compaction because the action of vibration sets the soil particles in motion and friction forces between soil particles are virtually demolished. During this vibration motion, the soil particles rearrange themselves to develop a dense state.
For normal soils, it is necessary to combine the action of vibration together with static pressure to breakdown the cohesion forces between soil particles in order to allow for better compaction. The static pressure of vibratory machines is adopted to exert a shearing force to eliminate the cohesion in clayey soils.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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Sir,
How is moisture content of soil determined using a moisture meter. Water reacts with calcium carbide producing gases and how is the moisture content shown on the guage.
Using Vibratory Roller in Non-Cohesive soils is OK and the static action with vibration can be applied to Silty and other fine grained soils of low plasticity,but in case of clayey sands and other soils having high plasticity Vibratory roller must be avoided as it may develop excess pore pressure hence developing the tendency to form cracks on the compacted soil bed. Sheep foot roller must be used to provide the kneading effect for better compaction and rubber Tyre roller should be used on the top layer for smooth surface finishing.