Modified Geogrid for Geobarrier System Incorporating Unsaturated Soil

Abstract

The Geobarrier System (GBS) is a three-component system to improve slope stability by combining capillary barrier, retaining system and vegetative cover. Currently, the retaining system of the conventional configuration is mainly controlled by the geogrid. However, the embedment length of the geogrid requires massive excavation which also leads to the longer construction duration. Considering this limitation, reducing the length of the geogrid while maintaining sufficient stability became the primary objective of this study. On the other hand, although earth nailing systems have been widely applied in slope stabilization practice, integration between geogrid reinforcement and earth mechanical anchorage has not been demonstrated within a unified framework. Therefore, J-pin attachments to the tip of geogrid are introduced in this study to compensate for the tensile resistance loss of the reduced geogrid embedment length. To conduct this, the conventional model with geogrid embedment length of 0.7 times the slope’s height (H) was modified into 0.6 H, 0.5 H, and 0.4 H. Attachment of J-pins were carried out gradually from the lowest layer of the geogrid. Analysis was conducted with two finite element software: PLAXIS 2D and ABAQUS, each with different purposes. PLAXIS 2D was utilized to perform unsaturated seepage analysis and mechanical analysis for calibration of ABAQUS numerical control settings. ABAQUS was used to perform mechanical analysis calibrated from PLAXIS 2D for modified models with J-pin attachments. Results show that modification on the geogrid embedment length has no significant influence on the pore-water pressure. The mechanical analysis concluded that J-pin attachment only effectively compensates for Model 0.6 H and 0.5 H with the optimum number is five J-pins, confirming that increasing anchorage density cannot compensate for insufficient geogrid embedment length. Furthermore, J-pin contributed up to 19.3% of total reinforcement force demonstrating effective composite interaction with geogrid.