Monitoring of swelling pressure in bentonite

Abstract

1 This paper presents a methodology for determining the radial swelling pressure that develops in a cylindrical plastic cell when the bentonite sample it contains is hydrated. Strains in the cylindrical cell wall are measured using strain gauges fixed to its external surface. The plastic cell material is assumed to behave in an elastic manner at the level of strain developed, and a best-fit solution for the pressure that results in the measured strains is calculated using an algorithm of optimisation. Even though the solution obtained is unique, it is also checked to verify that the calculated radial pressure results in the quantity of elastic energy developed in the cylindrical cell wall being a minimum. While the measurements obtained using the strain gauges allow the evolution of swelling pressure to be monitored from a qualitative viewpoint, the precise quantification of swelling pressure is difficult because not all the required pressure measurements were available. This paper demonstrates that the proposed methodology allows the qualitative monitoring of swelling pressures in bentonite cores during hydration. It also provides the basis for a quantitative procedure to be developed in the future.