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
