EVALUATION OF CHARACTERISTICS OF SUBGRADE STABILIZED WITH RANDOM POLYPROPYLENE SHORT FIBER

Construction of pavement on weak soil is highly risky because such soil is susceptible to differential settlements, poor shear strength and high compressibility. Reinforced earth technique is considered as an effective ground improvement method Therefore, in this investigation, polypropylene cross fiber was used as stabilization material where it was randomly included in to the soil at four different percentages. Three elastic modulus of the soil were also considered. The scope of the study was investigating the effect of fiber dosage and elastic modulus of the soil on subgrade normal strength, the modulus of subgrade reaction Ks and the plastic deformation. Moreover the relationship between the vertical applied stress and the corresponding vertical deformation was studied experimentally using loading test and theoretically using BISAR computer program. The effect of loading cycles on the accumulated elastic and plastic deformation was studied. Non linear relationships were achieved using computer program DATAFIT. From the laboratory test results, it was concluded that the cross polypropylene fibers can be considered as a good earth reinforcement material especially at fiber content of 0.5%. Moreover, equations of deformation ratio were produced to be used for estimating the vertical deflection and consequently the modulus of subgrade reaction Ks using computer program BISAR.