Novel experimental techniques to assess the time-dependent deformations of geosynthetics under soil confinement

A new experimental approach to assess the impact of soil confinement on the long-term behavior of geosynthetics is presented in this paper. The experimental technique described herein includes a novel laboratory apparatus and the use of different types of tests that allow generation of experimental data suitable for evaluation of the time-dependent behavior of geosynthetics under soil confinement. The soil-geosynthetic interaction equipment involves a rigid box capable of accommodating a cubic soil mass under plane strain conditions. A geosynthetic specimen placed horizontally at the mid-height of the soil mass is subjected to sustained vertical pressures that, in turn, induce reinforcement axial loads applied from the soil to the geosynthetic. Unlike previously reported studies on geosynthetic behavior under soil confinement, the equipment was found to be particularly versatile. With minor setup modifications, not only interaction tests but also in-isolation geosynthetic stress relaxation tests and soil-only tests under a constant strain rate can be conducted using the same device. Also, the time histories of the reinforcement loads and corresponding strains are generated throughout the test. Results from typical tests conducted using sand and a polypropylene woven geotextile are presented to illustrate the proposed experimental approach. The testing procedure was found to provide adequate measurements during tests, including good repeatability of test results. The soilegeosynthetic interaction tests were found to lead to increasing geotextile strains with time and decreasing reinforcement tension with time. The test results highlighted the importance of measuring not only the time history of displacements but also that of reinforcement loads during testing. The approach of using different types of tests to analyze the soilegeosynthetic interaction behavior is an innovation that provides relevant insight into the impact of soil confinement on the time-dependent deformations of geosynthetics.