The Subgrade Improvement of the Road Construction with Geotextile Reinforcement on Kolaka Clay

Civil Engineering Department, Faculty of Engineering, Tadulako University, Palu, Indonesia

^* Corresponding author: irdhiani@yahoo.co.id

Abstract

Subgrade is an important part of road construction. Construction built on fine-grained subgrade such as clay is very susceptible to damage. The purpose of this study was to determine the CBR value with and without geotextile reinforcement as well as to know the effect of geotextile placement on CBR value. Soil material samples was from Kolaka Village, Mori Atas District, North Morowali Regency, Central Sulawesi Province and the geotextile material used was the Woven UW-150 type. Geotextile used for CBR testing was 2 reinforcement sheets with 6 variations of geotextile placement that are successively on each space 1 and 2, 1 and 3, 1 and 4, 2 and 3, 2 and 4 and 3 and 4. The distance between spaces was 3 cm. According to the Unified Classification System, soil samples were included in the CH group (non-organic clays with high plasticity, fat clays), and according to AASTHO was classified in the A-7-5 (53) group, that is clay. Compaction test resulted an optimum water content of 20. 80% and maximum dry density of 1. 54 gr/cm3. Laboratory CBR values without reinforcement at soaked and unsoaked conditions were respectively 4. 61% and 9. 68%. The farther the distance between reinforcement as well as the farther the reinforcement distance to the ground surface, the greater the CBR value gained.