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Soil compaction is a vital part of the construction process. It is used for support of structural entities such as building foundations, roadways, walkways, and earth retaining structures to name a few. For a given soil type certain properties may deem it more or less desirable to perform adequately for a particular circumstance.
Soil bulk density, when determined at standardized moisture conditions, is an estimate of soil compaction. [3] Soil porosity consists of the void part of the soil volume and is occupied by gases or water. Soil consistency is the ability of soil materials to stick together. Soil temperature and colour are self-defining.
The pore space of soil contains the liquid and gas phases of soil, i.e., everything but the solid phase that contains mainly minerals of varying sizes as well as organic compounds. In order to understand porosity better a series of equations have been used to express the quantitative interactions between the three phases of soil.
Tilling the soil results in dislodging the cohesiveness of the soil particles, thereby inducing erosion. Chemical runoff. [17] [note 3] Reduces organic matter in the soil. [17] [note 4] Reduces microbes, earthworms, ants, etc. [20] Destroys soil aggregates. [17] [20] Compaction of the soil, also known as a tillage pan. [17] [20] [note 2] [note 3]
Soil compaction causes reductions in crop growth, yield and quality. Locally, these effects may have minor impacts on food security. If one aggregates the losses in food supply due to soil compaction, however, compaction may threaten food security. This is especially relevant for regions that are prone to droughts and floodings.
Soil bulk density, when determined at standardized moisture conditions, is an estimate of soil compaction. [60] Soil porosity consists of the void part of the soil volume and is occupied by gases or water. Soil consistency is the ability of soil materials to stick together. Soil temperature and colour are self-defining.
The AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, and is used as a guide for the classification of soils and soil-aggregate mixtures for highway construction purposes.
[4] [10] The plastic limit is the water content below which it is not possible to roll by hand the soil into 3 mm diameter cylinders. The soil cracks or breaks up as it is rolled down to this diameter. Remolded soil at the plastic limit is quite stiff, having an undrained shear strength of the order of about 200 kPa. [4] [10]