scope:

This Technical Specification is intended for determination of the compression, swelling and consolidation properties of soils. The cylindrical test specimen is confined laterally, is subjected to discrete increments of vertical axial loading or unloading and is allowed to drain axially from the top and bottom surfaces. The main parameters derived from the oedometer test relate to the compressibility and rate of primary consolidation of the soil. Estimates of preconsolidation pressure, rate of secondary compression, and swelling characteristics are sometimes also obtainable. The main parameters which can be derived from the oedometer test carried out on undisturbed samples are: 1) the compressibility parameters (mv, Eoed, Sc, Cc); 2) the coefficient of consolidation (cv); 3) the apparent preconsolidation pressure or yield stress (s'p); 4) the coefficient of secondary compression (ca); 5) the swelling parameters (Ss, Cs, swelling pressure). The fundamentals of the incremental loading oedometer test include: - the stress path corresponds to one-dimensional straining; - the drainage is one-dimensional and axial. The stress paths and drainage conditions in foundations are generally three dimensional and differences can occur in the calculated values of both the magnitude and the rate of settlement. The small size of the specimen generally does not adequately represent the fabric features present in natural soils. Analysis of consolidation tests is generally based on the assumption that the soil is saturated. In case of unsaturated soils, some of the derived parameters may have no physical meaning.