Experimental and analytical investigations of volume change behaviour of saturated expansive soils in oedometer test

The University of Tokyo, Department of Civil Engineering, 7-3-1 Hongo Bunkyo-ku Tokyo, Japan

^* Corresponding author: misahiraga.23@geot.t.u-tokyo.ac.jp

Abstract

The chemical and mechanical behaviours of saturated bentonite were experimentally and analytically investigated. A series of oedometer tests on saturated bentonite was conducted. By replacing the cell fluid during the oedometer test, one-dimensional osmotic consolidation and swelling behaviour were observed. The experimental results were simulated numerically using a constitutive model by considering the influence of electrochemical phenomena of clay mineral crystals on the macrostructural behaviour. It was concluded that the typical mechanical swellability of water-saturated bentonite in oedometer test is affected by a positive dilatancy behaviour due to the lower shear strength. After the osmotic consolidation test, a lateral contraction of the specimen in the oedometer was observed; this affected the compressibility during the subsequent mechanical consolidation. It was also concluded that the concentration of Na⁺ in the pore fluid affects the specific mechanical properties of bentonite.