In-Situ Tests for Dynamic Properties of Soils

Several problems in geotechnical earthquake engineering and soil dynamics require knowledge of dynamic soil properties. Problems involving dynamic loading of soils are divided into small and large strain response problems. For example a foundation supporting a well balanced machine represents a low strain situation. A structure subjected to an earthquake or blast loading or an off-shore struture subjected to storm loading exemplify a large strain problem. For solution of almost all problems dealing with dynamic loading of soil we need information on dynamic shear modulus and damping. The dynamic soil properties are affected by several factors. In fact it is the understanding of these factors which has lead to procedures for determination and rational evaluation of the dynamic soil properties for a given design or analysis problem (Prakash 1981, Prakash and Puri 1981, 1988, Woods 1991). The factors affecting the dynamic soil properties are: Type of soil and soil properties such as void ratio. Shear strain level. Nature of applied stress e.g. static, static + dynamic, or dynamic only. Confining pressure (mean effective confining pressure). Particle size and shape in coarse sands. Percent finer in fine grained soils. Depositional history of soil. Ageing. Degree of cementation. Mineral composition Stress history. Dynamic pre-strain. Stress path. Frequency of loading.