Effects of foams and polymers on the small strain behavior of kaolin

摘要

Soil conditioners such as polymers and foams arc often used in earth pressure balanced machines to improve the mechanical properties of the excavated soil and to guarantee safe tunneling with acceptable settlements. In clay soils, foams and polymers are expected to increase compressibility and workability and to reduce soil strength and adhesion potential of the soil mixture supporting the face of the tunnel. Application of conditioners often produces soft soil pastes, which do not behave like solid soil materials but also possess liquid and viscous properties. The detailed working mechanisms and effects on mechanical properties of the used chemicals arc still largely unknown. In this paper the drastic effects of a conventionally used polymer and foam on kaolin arc investigated. Undrained shear strength measurements using a newly developed vane shear device are analysed. The results show the dispersing power of polymers, increased viscous properties and drastically changed small strain behavior of the mixtures. All these effects are assumed to be a consequence of the reduced attraction forces between clay particles.