Strength and mechanical behavior of short polypropylene fiber reinforced and cement stabilized clayey soil

An experimental program was undertaken to investigate the effects of discrete short polypropylene fiber (PP-fiber) on the strength and mechanical behavior of uncemented and cemented clayey soil. In the present investigation, 12 groups of soil samples were prepared at three different percentages of PP-fiber content (i.e. 0.05%, 0.15% and 0.25% by weight of soil) and two different percentages of cement content (i.e. 5% and 8% by weight of soil), and unconfined compression and direct shear tests were carried out after 7-, 14- and 28-day curing periods. The test results indicated that the inclusion of fiber reinforcement within uncemented and cemented soil caused an increase in the unconfined compressive strength (UCS), shear strength and axial strain at failure, decreased the stiffness and the loss of post-peak strength, and changed the cemented soil's brittle behavior to a more ductile one. The interactions at the interface between fiber surface and soil matrix were analyzed by using scanning electron microscopy (SEM). It is found that the bond strength and friction at the interface seem to be the dominant mechanism controlling the reinforcement benefit. The behavior at the interface in fiber-reinforced uncemented soil was different from that in fiber-rei n forced cemented soil. The micromechanical properties of fiber/matrix interface were influenced by several factors, e.g. binding materials in soil, normal stress around the fiber body, effective contact area of the interface and fiber surface roughness, etc. (C) 2006 Elsevier Ltd. All rights reserved.