Abstract
In order to use the advantages of unconfined compression tests, a new testing procedure using S (or Small size) specimens (15 mm in diameter and 35 mm in height) is proposed and a new portable unconfined compression test apparatus with suction measurement is outlined. The effect of specimen size on unconfined compressive strength properties of natural deposits is discussed from laboratory tests. The standard deviations of the ratios of qu and E50 values of the S specimens to O (or Ordinary size) specimens (35 mm d and 80 mm h) were in the range of 0.09 to 0.16. The 10% variation from the mean value reflects the homogeneity of soils since the coefficient of variations of the undrained shear strength for the undisturbed and reconstituted soils were 8% to 17% (Matsuo and Shogaki, 1988). In an engineering sense, there was no difference in shear strength and deformation characteristics between the S and O specimens for soils having plasticity indexes ranging from 10 to 370 and unconfined compressive strengths of 18 kPa to 1000 kPa, that were taken from 26 different sites in the United Kingdom, Korea and Japan. These soils consisted of Holocene and Pleistocene clays plus diatomaceous mudstone and highly organic soils.
