LABORATORY STUDIES ON FIBER REINFORCED SOILS

Abstract

Studies indicate that around 75% of the failures of the pavement are due to failure of the subgrade only. Stabilization of weak soil has been the age old practice of improving subgrade soil. The conventional soil improvement practices are generally expensive, involving large quantity of costly materials and construction operations. Therefore, soil reinforcement is an effective and reliable technique for strength and stability of soils. Traditional methods of earth reinforcement consist of introducing the continuous inclusions like strips, fabrics, and grids into an earth mass. These are normally oriented in a preferred direction and are introduced sequentially in alternating layers. An earth mass stabilized with discrete, randomly distributed fibers resembles traditional earth reinforcement in many of its properties. One of the main advantages of randomly distributed fibers is the maintenance of strength isotropy and the absence of potential planes of weakness that can develop parallel to oriented reinforcement. The laboratory studies were conducted on sandy and clayey soils reinforced with Polypropylene fiber. The fiber aspect ratio was varied from 50 to 100 and fiber content from 0.75% to 3.0% by weight of dry soil. The tests like, CBR, E- value,, static triaxial and repeated triaxial were conducted on two types of soils. The results indicate that The CBR value of reinforced sand is 2.9 times its unreinforced value. The elastic modulus of reinforced sand and clay soil is 236 kg/cm2 and 190.7 kg/cm2 at a confining pressure of 1.2 kg/cm2, which are respectively 9.44 and 4.76 times these values for unreinforced samples. Angle of internal friction (0) increases and cohesion decreases due to reinforcement by fiber. The resilient strain and permanent strain at a given deviator stress are higher for unreinforced samples than reinforced samples. Reinforced samples have higher resilient modulus than that of unreinforced soils.