Improvement Of Expansive Subgrade Soil Using Geotextile And Sugarcane Bagasse Ash (Scba): A Case Of Jimma City

Abstract

Most parts of Ethiopia have expansive clay soils, which have challenging engineering properties and present challenges for infrastructure construction in this place. The cost of construction significantly increases due to the need to transport materials from quarries that are far away to replace problematic soils with those that have appropriate engineering properties. Large-scale building material transportation harms the environment and is not a sustainable practice. The main objective of this research was to improve expansive subgrade soil using non-woven Geotextile and sugarcane bagasse ash (SCBA). Two representative samples were collected, from Jimma City next to Bechobore (Technic Sefer) and inside the campus of Jimma institute of technology close to the new stadium, to address the specified aims. The soil samples were collected at a depth of 1.5 meters below the ground surface. The preparation and testing of the soil sample was based on the various test requirements and standards set by the American Society for Testing and Materials (ASTM) and American Association of State Highway and Transportation Officials (AASHTO) procedures. These tests included X-ray diffraction, moisture content, grain size distribution, specific gravity, free swell, Atterberg limits, compaction, CBR, and unconfined compressive strength. To examine the sample, this research used expansive clay soil, expansive soil + Sugarcane bagasse Ash (SCBA), expansive soil + non-woven Geotextile, and expansive soil + SCBA + non-woven Geotextile. Non-woven Geotextile materials were included at different depths during the molding process for California bearing ratio (CBR). Both descriptive and analytical methods were used to analyze the results. According to AASHTO and the unified soil classification system (USCS), the test results showed that the natural subgrade soil is A-7-5 and highly plastic clay (CH). For both samples, the 96-hour soaked CBR result for the optimum amount of sugarcane bagasse ash was changed from 2.19% and 2.23%, at their natural state, to 6.88% and 6.92%, respectively. For the optimum dosage of SCBA plus nonwoven Geotextile (inclusion of it at two depths), the CBR values increased to 19.67% and 20.17% for samples A and B. Generally, the use of sugarcane bagasse ash has improved the soils to a moderate level. Bagasse ash has both economic and environmental advantages and can be used as a soil-improving ingredient in non-woven Geotextile