Stabilization of sand using different types of short fibers and organic polymer

Abstract

Due to the loose packing of natural sand, great efforts have been intended to achieve its stabilization and prevent associated engineering failures. As a new soil reinforcement technique, the combined treatment using chemical stabilization and fiber reinforcement has drawn increasing attentions. The focus of this study is to investigate the effect of short fiber types (including polypropylene, basalt and glass fibers) on the mechanical performance of polyurethane (PU) polymer treated sand. Unconfined compressive and tensile tests were performed and analyzed to infer the degree of strength enhancement with different types of fiber reinforcements. Also, intrinsic mechanism and variation in the microstructure were studied by scanning electron microscopy (SEM). The results showed that the strength properties and brittle behaviors were improved greatly by fiber incorporation in comparison with only polymer reinforcement. With same content, polypropylene fiber imparted greater strength to the treated soil due to its well flexible structure and strength properties as compared to other fibers. As observed, 0.8% polypropylene fiber addition led to an increment in compressive and tensile strength by 108.07% and 295.42% respectively, while with same content basalt fiber imparted 63.91% and 147.06%, and fiberglass imparted 47.92% and 253.08% respectively. Additionally, the change in stress-strain curves and failure mode and enhanced value of brittleness index (about 2 to 4 times) indicated increasing ductility. The presence of polymer provided cementation the soil matrix, which also led to great bond strength in grains contacts and fiber-grains contacts. The fibers exhibited stretching and breakage rather than sliding through the soil during failure, which was commonly observed in monofilament polypropylene fiber reinforcement. Soil mechanical properties were also influenced by dry density. As observed, the strength properties got better with increasing dry density while the brittleness became worse, due to enhanced interfacial friction at fiber-sand and sand-sand interface. It was observed that the soil reinforcement with polymer and fiber displayed high strength and modulus for its efficient use being influenced by softness, strength properties, density and size of different fiber types.