초록
By use of thermal bonding method, 2-phase geotextile composed of bonded and nonbonded parts for reinforcement was made from a needle punched polypropylene nonwoven to analyze the viscoelastic behaviors. The yield strain of 2-phase geotextiles is lower than that of simply needle punched geotextile and this is due to the increase of stiffness by uniform distributions of bonded parts. The interpretation of stress relaxation behaviors of 2-phase gootextile was based on Schapery's theory. The equilibrium state of stress relaxations approached to 10 sec independent of additional strains, and relaxation times existed within the range of 10 sec. The strain function, h(e), was divided into elastic and plastic regions and the transition between these regions occurred at 15∼25% strain ranges. Finally, the relaxation behavior of bonded parts was governed by (∞) and the behavior of unbonded parts was governed by (0)- (∞).