Soil is man’s oldest, perhaps most common, and probably the most complex construction material. Because of its function as the support for virtually all structures, soil become an indisensable component of the construction and, therefore, in a broad sense, plays a mosr prominent role in civil engineering design. hence, in spite of its complexity, we must work with it; we must determne its behaviour under load; we must evaluate its interactions with the structures it supports. in the final analysis, we must fit it into its designated role such that a given design is economical and safe. these are rather demanding tasks that ordinarily  require a working knowledge of soil mechanics, some relevant experience, and a great ideal of engineering judgement.

Up to this point the typical civil engineering student has taken a series of courses in mathematics, analythical mechanics, or mechanics of materials in which the problem as well as the variables were relatively well defined. for example, the student may be able to readily solve for the reactions, moments, stresses, or deflections in a continuous-steel beam of a given size and length, which supports a designated load. the student may also knoe quite well that the modulus of elasticity for steel is a constant, that the material is reasonably homogeneous nd a quality-controlled product. hence, the behaviour of steel under load can be predicted with reasonable accuracy. by contrast, the practicing civil engineer may be called upon to analyze, design, or construct a structure whose design parameters are not nearly as well defined. for example, let us imagine the problem of designing a dam, a dock, a tower, and airport, a retaining wall, a highway-all structurs founded on soil or ledge. in their overall scope, this projects encompass much more than the idealized or hypothesized conditions and variables cited above. these are situations where one must employ the use of good judgement to solve the problem. in other words the interaction of reasonably “homogeneous” ateel beam, supported by “elastic” columns that rest on rather “unpredictable” material such as soil poses a problem that is not clear-cut, and one that may or may ot have a ingle and unique solution.

Geotechnical Engineering is commonly regardedas the whole of two parts : Soil Mechanics and Foundation design (or Foundation engineering). Soil Mechanics encompasses topics associated with the physical and index properties of soi, waterflow through soils, stress and deformation  phenomena in soils, strength parameters, bearing capcity, field exploration techniques. laboratory testing, and a brief reflection on geology. Foundation Design/Foundation Engineering focuses on bearing capacity, methodologies for designing various types of spread and combined footings, retaining wall, sheet piles, deep foundations and techniques for site improvements.