Geotechnical characterization of a novel material obtained by injecting a closed cell expansive polyurethane resin into a sand mass

Abstract

This paper reports the findings of experimental studies on a novel application of a closed cell expansive polyurethane resin injection into a sand mass, regarding some common engineering properties. Previous papers on injecting expansive polyurethane resins into sand masses as mitigation measures of different hazards, e.g., liquefaction, settlements and seismic displacements, deal with the open cell sub-class of polyurethane resins. Seeking to make up for the shortcomings of open cell methods, the paper addresses a prototype application of a closed cell polyurethane resin for ground improvement/control on sands. A new system for the preparation of the sand-resin mixture (SRM), which mimics the field application conditions, is introduced. It allows to inject the polyurethane resin into saturated sand with a prescribed mass density. The results of an extensive laboratory testing program are presented and discussed regarding some relevant engineering properties, e.g., Young’s modulus, Poisson’s ratio, uniaxial compressive strength and peak and residual friction angles. Namely, it was concluded that the SRM may be studied as a soft rock and that it shows an essentially plastic behaviour for large deformations, as well as a high shear strength and low permeability. It is envisaged that these fundamental results may encourage and assist the execution of in situ tests under controlled conditions, concerning the resin injection and its performance assessment, further promoting the application of closed cell polyurethane resins in geotechnical practice in a near future.