Rate- and Time-Dependent Mechanical Behavior of Foam-Grouted Coarse-Grained Soils

This paper experimentally investigates the mechanical properties of foam-injected gravel by means of uniaxial compression tests and uniaxial creep tests. Bonding of noncohesive soils by foam injection is a novel soil improvement method that can be applied for the stabilization of cohesionless soils at the tunnel face and behind soldier pile walls. Limited data on the mechanical behavior of foam-injected soils is available in the literature. A method for the preparation of homogeneous and reproducible test specimens was developed. The testing program included the variation of the factors that influence the mechanical behavior (e.g., initial soil density, grain size, strain rate, curing time, and stress level). Similar to cemented soils, the foam-injected soils show an elastoplastic stress-strain response and softening beyond the peak. The mechanical behavior is time-, stress- and rate dependent. The strength and stiffness can be described by the porosity-binder concept considering the influence of strain rate, soil density, and foam content.