PORE SIZE DISTRIBUTION OF CLAYEY  SOILS MEASURED BY MERCURY INTRUSION POROSIMETRY AND ITS RELATION TO HYDRAULIC CONDUCTIVITY

HIROYUKI TANAKA, DINESH R. SHIWAKOTI, NAOKI OMUKAI, FUSAO RITO, JACQUES LOCAT and MASANORI TANAKA

ABSTRACT: Pore Size Distribution (PSD) of naturally deposited clayey soil samples recovered from various parts of the world and at varying depths was measured by Mercury Intrusion Porosimetry (MIP). In addition to naturally deposited samples, the artificially mixed soils, namely Singapore clay with Toyoura sand or diatomite, are studied in order to know the influence of grain size component on the PSD. Characteristics of the PSD were represented by the mean pore size (D_p50). As an application of the PSD characteristics to the practical geotechnical engineering, an attempt has been made to relate the hydraulic conductivity (k) with the PSD. The following interesting findings are obtained:
1) With an increase in the consolidation pressure (p�f), D_p50 also decreases in the same manner as that of the e-log p�f relation. 
2) The range of D_p50 for naturally deposited soils is relatively narrow, namely between 0.03 and 2 mm, except for London clay which is the old deposit clay, i.e., Tertiary.
3) It is found from the artificially mixed soils that D_p50 generally increases with increase in silt and sand content. 
4) There is a unique relation between the hydraulic conductivity (k) and nD_p50², where n is the porosity.

Key words: clayey soil, diatomite, hydraulic conductivity, mercury intrusion porosimetry, permeability, pore size distribution, Toyoura sand (IGC: D6)