Effect of geosynthetic inclusion on the bearing ratio of two-layered soil

In this article, the load-settlement characteristics of unreinforced and reinforced two-layered soil during the loading process are investigated. A series of bearing ratio tests was performed on a granular soil as the base layer overlaying a cohesive soil as the subgrade layer. Three reinforcing conditions (unreinforced, reinforced with nonwoven geotextile, and reinforced with geogrid) at the interface of layers, with four compaction moisture contents (CMCs) of the subgrade layer and three thicknesses of the base layer for both soaked and non-soaked conditions are considered. The results show that the CMC of the subgrade layer has a significant effect on the behavior of two-layered soil, such as swelling amount and the efficiency of the reinforcements. Reinforcing with geogrid resulted in a considerable increase in strength of the soaked samples due to adhesion between geogrids and clayey subgrade layer. For nonwoven geotextiles, strength of the two-layered soil decreased at shallow penetration depths due to reinforcements; and as the penetration increased in depth, the strength also increased. Also, it was found that with decreases in base layer thickness, the test variable's value (i.e., CMC), and the type of geosynthetic reinforcement have significant effects on the behavior of two-layered soil.