Multiscale transmissivity study of drain-tube planar geocomposites: effect of experimental device on test representativeness

摘要

Hydraulic transmissivity is the most important design parameter of geocomposites usednfor in-plane drainage applications. This paper presents an in-depth investigation of the hydraulicnbehaviour of drain-tube planar geocomposites (DTPGs) and characterises the locations and causes ofnhead losses based on a multiscale experimental approach using three different apparatus. Innparticular, a transmissivity rig that accommodates specimens up to 1 m2 was developed to define thenminimum representative surface area required to characterise DTPGs. The experimental data acquirednin this study support a theoretical relationship linking head losses that occur within DPTGs to flownrate. This relationship is used to analyse the results obtained with other transmissivity rigs and tonidentify the key locations where head losses develop. In addition, evidence that Colebrook’s equationncan be applied to corrugated tubes is presented. Based on this study, it is concluded that thenmeasured DTPG transmissivity is significantly affected by specimen length and by the experimentalndevice used to make the measurement. For example, the DTPG transmissivity measured innaccordance with ASTM D4716-08 was found to be 14% lower than the actual DTPG transmissivity.