Soil compaction is very important and essential procedure in the process of road construction, construction of airfields, foundations, parking lots, residential buildings and many other construction projects. The durability and stability of the ground can only be increased through proper soil compaction. Any failure to achieve this at the beginning of the construction process will result in huge damages and costly repairs. The soil compaction is defined as a process of mechanic densification of earth. It is best achieved by using mechanical energy which is provided by compaction machines known as compactors. The ground is compacted by removing the water and the air from between the soil particles. A soil that is well compacted prevents the moisture from getting in and out very easily.
The compaction process provides the following:
- maximizes the amount of the weight that is going to be put on top of the soil
- prevents any frost damage
- minimizes the contraction of the soil and also the swelling of the ground
Several methods can be used for determining the degree of compaction that is needed. The most commonly used ones are:
To determine if the soil needs to be compacted, soil samples are tested and analyzed in a lab. One particular and widely used lab test for soil compaction is the Proctor Compaction Test. In this test, the soil is compacted at various moisture levels. There are two Proctor tests that are used: The Standard Proctor Test and The Modified Proctor Test. The standard proctor test is generally used for the construction of small parking lots, sidewalks and residential buildings. The modified proctor test, on the other hand, is used for the construction of large projects such as highways and airport runways.
Field compaction of the soil is generally accomplished by using different types of soil compactors. The three most commonly used compactors are: sheep foot roller compactors which are used for clay and silty soil, smooth drum roller compactors used for granular soil, and vibratory roller compactors which are also used for granular soils. Several important factors can affect the degree of compaction that is needed such as moisture level of the soil and the depth of the fill. Usually, a percentage of optimum compaction is given to the construction engineer and this percentage is known as the Relative Density or R% which ranges from 90%- 95%.
Determining the degree of the soil compaction which is needed for particular construction project is essential for getting the relative compaction of the soil. The most commonly used field tests for soil compaction are: Sand Cone Method, Drive Tube Method and the Nuclear Method. All three field tests provide very accurate results for determining the degree of soil compaction that is needed.