Interface characteristics and stability mechanisms of bubbles in high-concentration bentonite slurry

Abstract

Foam and slurry are important materials for preventing spewing of the earth pressure balance (EPB) shields, but their interaction at the interface level is not entirely understood. Herein, an anionic surfactant was used to foam bentonite slurry with a concentration of 10–30 wt%. The mechanism of the slurry on the foamability of the surfactant and the bubbles stability were analysed through surface viscoelastic modulus, ζ-potential, FT-IR, surface tension, contact angle, and microscopic observation. The results show that the bentonite slurry forms a stable three-dimensional grid structure, which increases the surface tension and free energy required for the formation of the gas–water interface. Surfactants are adsorbed on the bound water layer on the surface of bentonite particles. This increases both the electrostatic repulsion of system and the hydrophobicity of the particle and forms a multi-layered gas–water interface with high viscoelasticity, thus slowing down the drainage, coarsening, and coalescence.