Physical stabilization of expansive subgrade soil using locally produced geogrid material

Abstract This paper illustrates application of a locally produced geogrid material for strength improvement of expansive subgrade soil. Samples of black, soft soil predominating the study area were collected from south western parts of Modjo town, inside the rift valley region of central parts of Ethiopia. X-Ray diffraction as well as index property tests were executed to identify and categorize the expansiveness of the highly plastic soft soil. The effects of two locally manufactured geogrid reinforcement materials; namely, polypropylene (PP) and high density polyethylene (HDPE) on the California bearing ratio (CBR) values of the expansive soil have been investigated. The test results indicated that the use of the geogrid reinforcement can significantly improve the bearing capacity of weak subgrade soil. The soaked CBR of the untreated soil sample, which was about 2.98%, was able to be raised to 10.16% and 7.48% by the application of PP and HDPE type of geogrid respectively, that were placed at 0.35H from the top of specimen. The research demonstrated the potential of using locally produced geogrid material for the improvement of weak subgrade soil.