Compressibility behavior of conditioned sandy clay considering the physical degradation of foam: tunneling issue

Surfactants in the form of liquid foam are commonly used for ensuring the fluidity of conditioned soil during shield tunneling in mining zone. The compressibility can be significantly affected, depending on the percentage of fine soil. Thus, this paper investigates the compressibility of foam-conditioned fine soil. Oedometric tests as a function of the percentage of foam have been performed. Foam’s stability was analyzed, considering a laboratory soil made from 40% kaolinite and 60% of sand and mixed with a foaming agent based on an anionic surfactant. Experimental results showed that the foam stability was manifested through a reduction of the foam’s volume followed by liquid drainage, under loading and due to the foam’s physical degradation over time. The compressibility increases with the adding rate of the foam in the soil. Therefore, consolidation and foam’s degradation over time are two factors that allow the recovery of the compressibility property of conditioned soil.