Studies on the performance of geocomposite reinforced low-permeable slopes subjected to rainfall

Abstract

Slope instability due to rainwater infiltration is a common problem in many parts of the world, and causes thousands of deaths and damages to infrastructures annually. The problem becomes severe if the soil within the slope has low permeability, and cannot dissipate the pore water pressure generated during the rainfall event. In recent times, the unavailability of good quality backfill material has led to the use of locally available low-permeability soil in reinforced slopes/walls construction. A viable alternative is the inclusion of geocomposites within the slope, to provide the drainage and reinforcement actions necessary to maintain slope stability against rainfall. In the present paper, the effect of rainfall on the seepage characteristics and global stability of slopes with and without geocomposites was investigated numerically using Geostudio (2012). For this purpose, a typical low-permeable slope having 2V:1H inclination and 7.2 m height was considered, and the change in matric suction in the slope with time was studied by subjecting it to a medium rainfall of intensity 22 mm/hr for a duration of 24 hours. It was observed that, the low-permeable slope exhibited high pore water pressures and low factor of safety under the applied rainfall intensity. However, the same low-permeable slope when provided with geocomposite layers, showed significant lowering of phreatic surface and reduced pore pressures, and was stable even 24 hours after completion of duration of rainfall. A parametric study was also conducted to determine the optimum position of placement of geocomposite layers within the low-permeable slope subjected to rainfall. The results indicated that the placement of gecomposite layers at bottom portion of the slope was found to be most effective, as compared to middle and top positions. The use of dual-function geocomposites within slopes subjected to rainfall thus eliminates the necessity of procuring expensive high-permeability fill materials, thereby economizing the project.