Interaction of nonwoven needle-punched geotextiles under axisymmetric loading conditions

Geotextiles have been successfully used for reinforcement of unpaved roads on soft subgrade to improve the performance of a reinforced fill layer plac ed on soft ground. The tension-strain behavior of a nonwoven needle-punched geotextile under axisymmetric loading condition as well as the mechanism a nd effects of the different grades of geotextile on the increase in bearing capacity of reinforced unpaved roads over weak subgrade under traffic load were considered. The strain energy capacity concept is proposed to describ e the tension-strain of geotextile under an axisymmetric loading condition. Modified CBR tests on soft and weathered clay overlain by compacted sand a s well as on soft and weathered clay overlain by compacted sand reinforced with fix- or free-end nonwoven needle punched geotextile were carried out. Finite element method (FEM) using the PLAXIS software was utilized to back- analyze the results of the modified CBR tests. No significant difference be tween in-air and in-soil stiffness has been found for geotextile reinforcem ent of unpaved road. The calculated results indicate an additional load cap acity due to the presence of the geotextile using an axisymmetric stiffness which demonstrated a significant contribution of membrane action by the di fferent types of geotextile on the increase in bearing capacity of soil-geo textile system. The effects of the different types of geotextile obtained i n this study can be used to preliminary select the appropriate grades of no nwoven needle-punched geotextile corresponding to the allowable rat depth i n the design of the reinforced unpaved roads under traffic load. (C) 2001 P ublished by Elsevier Science Ltd.