Improvement of Sand Subgrade Soil Strength with Geogride Reinforcement

Abstract

The quality and life of pavement is greatly affected by the type of sub-grade, sub base and base course materials. The most important of these are the type and quality of sub-grade soil. But in Iraq most of the flexible pavements are needed to be constructed over weak and problematic sub-grade. Flexible pavements constructed on weak subgrade with low California bearing ratio (CBR) are required to increase its total thickness. On the other hand the decrease in granular subbase course material has forced to a search for improvement in problematic subgrade soil to be suitable construction materials. The present research aims to study the effect of geo-grid reinforcement on CBR of sub-grade soil and on total pavement thickness. The soft sand type of soil and one type of geo-grid were selected for this study. From the study it is clear that there is considerable improvement in CBR of sub-grade due to geo-grid reinforcement. In case of without reinforcement (Geo-grid) the soaked CBR value was 2.14% and when geo-grid was placed at 0.2H from the top of the specimen the CBR increases to 12.84%. Also, the reinforcement of subgrade with geogride at 0.2 subgrade layer thickness from subgrade top will reduce the total pavement thickness by 60%.