Soil engineering, soil mechanics or geotechnical engineering is one of the youngest disciplines of civil engineering involving the study of soil, its behaviour and application as an engineering material. Geotechnical engineering is the application of laws of mechanics and hydraulics to engineering problems dealing with sediments and other unconsolidated accumulations of solid particles produced by the mechanical or chemical disintegration of rocks regardless of whether they contain an admixture of organic constituents or not.
Geotechnical engineering can also be defined as a branch of civil engineering concerned with the engineering behaviour of the earth’s materials. It includes investigating existing subsurface conditions and materials; determining their physical/mechanical and chemical properties that are relevant to the project considered and assessing the risks posed by site conditions; designing earthworks and structure foundations and monitoring site conditions, earthwork and foundation construction.
A typical geotechnical engineering project begins with a review of project needs to define the required material properties. This is followed by a site investigation of soil, rock, fault distribution and bedrock properties on and below an area of interest to determine their engineering properties, including how they will interact with, on or in a proposed construction. Site investigations are needed to gain an understanding of the area in or on which the engineering will take place. Investigations can include assessment of the risk to humans, property and the environment from natural hazards, such as earthquakes, landslides, sinkholes, soil liquefaction, debris flows and rock falls.
A geotechnical engineer then determines and designs the type of foundations, earthworks and/or pavement subgrades required for the intended man-made structures to be built. Foundations are designed and constructed for structures of various sizes such as high-rise buildings, bridges, medium to large commercial buildings and smaller structures where the soil conditions do not allow code-based design. Foundations built for above-ground structures include shallow and deep foundations. Retaining structures include earth-filled dams and retaining walls. Earthworks include embankments, tunnels, dikes, channels, reservoirs, deposition of hazardous waste and sanitary landfills. Geotechnical engineering is also related to coastal and ocean engineering. Coastal engineering can involve the design and construction of wharves, marinas and jetties. Ocean engineering can involve foundation and anchor systems for offshore structures such as oil platforms. The fields of geotechnical engineering and engineering geology are closely related and have large areas of overlap. However, the field of geotechnical engineering is a specialty of engineering, whereas the field of engineering geology is a specialty of geology.
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