Geotechnical investigation and testing - Laboratory testing of soil - Part 5 : incremental loading oedometer test
ISO/TS 17892-5:2004 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) compressibility parameters;
2) coefficient of consolidation;
3) apparent preconsolidation pressure or yield stress;
4) coefficient of secondary compression;
5) swelling parameters.
The fundamentals of the incremental loading oedometer test include: stress path corresponds to one-dimensional straining; 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.