Laboratory experiments on performance evaluation of geocomposite drainage materials

Abstract

Method of geocomposite drainage systems (GCDs) is relatively new and has been used as an alternative drainage system for geotechnical applications. The advantages of this system are cost- and time efficiency, environmentally sustainable, and at the same time, having comparable or higher drainage capability compared to current practices. However, the geocomposite materials, which are the main products of the GCD systems, need to meet certain criteria that are required for the sufficient drainage systems. These criteria are mainly related to their hydraulic and mechanical parameters that control the drainage capacity and durability of the systems during/after the construction. In this study, laboratory testing and evaluation of five different commercially available geocomposite products are conducted to improve the understanding of their physical, hydraulic and mechanical properties. Physical properties are defined by measuring their thicknesses and apparent opening sizes. Hydraulic parameters; permittivity (volumetric flow rate of water in normal direction) under various hydraulic head was measured using a constant-head equipment. Additional transmissivity and flow rate are defined under various hydraulic gradient and normal compressive stresses using in-plane flow rate testing apparatus. A number of strength testing; compressive strength, grab tensile strength, elongations, trapezoidal and puncture strength are conducted to evaluate the mechanical behavior of the geocomposite products. Results show that the parameters defined for each product are in the same order of magnitude in corresponding testing program, yet some differences are observed when compared with the manufacturer values. The reason of differences and recommendations on the selection of standard testing methods are discussed. Use of a factor of safety (FS) was suggested in the design of geocomposite drainage system when selecting the geocomposite materials.