ABSTRACT
This paper provides an overview of recent experimental results regarding the influence of pressure on foam and foam-conditioned sands. A series of experimental investigations were performed using pressurized chambers and a foam capture device to investigate the fundamental and engineering properties of foam and foam-conditioned sand. Foam development experiments reveal significant energy losses through the bead-filled generator and foam transport pipe. Energy loss in the generator increases with foam/air velocity, pressure and generator length. The hydraulic gradient in the foam transport pipe increased sharply with a decrease in pipe diameter, affiliated with a decrease in foam bubble size. An investigation of foam stability showed that foam and air volume loss with time is insignificant during significant liquid volume loss. During this period of time, air bubbles are coalescing to form bigger bubbles yet very little air (e.g. less than 2–3%) is released to the atmosphere. The corresponding engineering properties of foam, such as compressibility, elasticity and plastic strain accumulation do not change appreciably. Foam was also found to be much less time-varying under higher pressure, largely due to smaller, more uniform bubbles. A series of conditioned sand experiments under pressure confirmed the role of relative density of conditioned soil in assessing the efficacy of conditioning. The transition pressure, above which the foam governs behavior and below which the soil governs behavior, increases with increasing foam. Shear strength and abrasivity increase rapidly at chamber pressures above the transition.
