Formation of Soil
Soil is a combination of minerals and organic constituents in solid, gaseous, and aqueous forms. It truly possesses layers of particles that differ in physical, mineralogical, and chemical properties from the original materials because of the actions of the atmosphere, hydrosphere, and other causes. Soil particles are the products of broken rocks changed by the impacts of the chemical and environmental effects that include weather and erosion. Soil particles fill loosely creating a formation of soil filled with pore spaces. The modes of soil formation are important to study since they help in determining properties of some soils. Knowing the type of soil one has to deal with can easily tell about its cohesiveness, adhesiveness, acidity, and other related factors. We cannot draw any concrete inferences merely by doing soil studies, but we surely can narrow our research parameters by studying the basic characteristics of soil, such as color, texture, and nature of soil.
Basic characteristics of soil
In general, soil consists of solid, liquid, and gas phases. Therefore, its properties are determined by the interactions among these phases and by applied stress. Varied categories of the solid phase making up the soil include clay, non-clay minerals, and organic material. These latter three are classified according to their size: as clay, sand, and gravel. While the liquid phase is essentially made up of water containing the available organic compounds resulting from chemical spills, wastes, and ground water, the gas phase is usually air. A science related with the chemistry, structure, and physical properties of minerals, soil mineralogy establishes the size, form, chemical properties, compressibility, and load carrying capability of the soil particles. Soil structure depends on the arrangement of particles, groups of particles, pore spaces, and the composition. Based on these basic characteristics, it can be determined what type of structure needs to be built and what external support measures, if any, has to be taken for the structure to last long and bear the effects of earthquake, water seepage, and other external factors.
Another important factor that needs to be studied in order to make a structure very strong and durable is the consolidation of soils. Consolidation is one kind of process according to which the volume of soil will get reduced due to the application of some stress, because of which the particles of the soils would pack together firmly, thereby decreasing their volume. Removal of the applied stress will result in the soil rebounding and recovering some of the volume lost during the process of consolidation. In studying consolidation, the key factors to be looked upon are the rate of consolidation and the amount of consolidation. Another important factor is permeability of the soil. All the factors are closely associated with each other and they affect the overall design and construction process.
For instance, in fine grained soil with low permeability, if a structure is to be made on it, the water will flow little through the voids of the soil. If there is large water content in this soil, it may cause the structure to sink due to its weight. The process of consolidation in fine grained soils is slow. However, coarse grained soils do not have complicated pore water extraction since the pore water moves freely throughout the region. The rate of consolidation will get influenced by the history of soil, nature of the soil, and the load on the soil. Thus, all the factors like the content of water, permeability, consolidation, liquid limit, are analyzed collective barring a few exceptions.
Some of the major studies in this discipline are lateral earth pressure, bearing capacity of soil, and slope stability analyses. All these studies always help a civil engineer to design better structures and construct them. Indirectly, these studies help in mitigation of risk too because we know beforehand how the mass of soil is going to behave, so precautionary measures can be taken at the time of construction itself.
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