The strength of unsaturated bentonite-enhanced sand

Abstract

A modi®cation to Rowe's stress-dilatancy equation is presented that extends its range of application to include unsaturated soil behaviour. The results of a programme of constant water content triaxial tests on unsaturated bentonite-enhanced sand (BES) are reported, together with those of a programme of saturated drained triaxial tests on the sand. It is shown that the variation in the rate of dilation at failure with the sand relative density is similar for the two materials. It is proposed that the packing and friction angle of the sand particles and the degree of saturation control the shear strength of unsaturated BES containing modest amounts of bentonite, and that the shear strength of the bentonite component can be ignored.

Determination of Residual Concentration of Active Polymer in a Polymeric Support Fluid

“…It was chosen for its well characterized chemical structure and properties (e.g. Kawatra and Ripke 2001;Stewart et al 2001). Also sodium bentonite, because of its high specific surface area, should represent a worst-case sorption scenario for polymer sorption in the field (note that the best-case scenario in terms of sorption would be drilling in clean coarse sand).…”