Experimental Study on Volume Change Indices of Bentonite Soils

Introduction Bentonites are used as barrier and backfillingmaterials in many countries for storing the high leveltoxic wastes1-4]. The clays have several advantageousproperties with regard to the hydro-mechanical re-quirements; for exmple, low permeability, highswelling capability and good thermal conductivity aresome of the features. Determination of swelling prop-erties of bentonites is important and has been carriedout by many researchers5,6]The volume change behavior of bentonites ispri…

Experimental Study on Volume Change Indices of Bentonite Soils

This paper reports experimental results regarding statically compacted clay specimens to study the volume change behavior of bentonites. The volume change indices such as the coefficients of compressibility, volume compressibility, and consolidation (i.e. av, mv and cv respectively) and the saturated coefficient of permeability k at different surcharge pressures were determined with the commonly adopted procedures. The swell potentials, swelling pressures, different phases of the swollen specimens were analyzed for the volume change behavior during compression. Experimental results revealed that the swell potential is dependent on the initial dry density, the initial water content and the vertical pressure at which the clay specimens were allowed to swell. The swelling pressure was found to be similar for the specimens with varying water content, showing strong dependency on the initial void ratio. The compression indices (viz. mv and av) of saturated specimens decreased with an increase in the vertical pressure. About 80% to 90% of the volume change occurred in the primary compression phase under any given vertical pressure. The coefficient of consolidation cv and the saturated coefficient of permeability k decreased with an increase in the vertical pressure.