Influence of Rock Powder on the Geotechnical Behaviour of Expansive Soil

Expansive soils create challenges in civil engineering projects due to their tendency to significant volume changes with variation in moisture content. In this study, an experimental study was carried out to evaluate the influences of rock powder on the geotechnical properties of expansive soil. This paper presents the results of some index and engineering properties of expansive soil mixed with the rock powder, including Atterberg limits, compaction, free swelling, unconfined compressive strength (UCS), California bearing ratio (CBR), direct shear, and permeability at different percentages (0%, 8%, 16%, 24%, 32, and 40% by dry soil weight). The results reveal that the index properties, optimum moisture content, free swelling, cohesion, and coefficient of permeability decrease with the addition of rock powder up to 40%. Whereas, the maximum dry density, UCS, and CBR increase up to 24% of rock powder thereafter reversed. Furthermore, the internal friction angle increases by 95.32%, while the subbase thickness layer for a roadway could be reduced by 40% with the addition of 40% rock powder to the soil samples. Based on the test results, the optimum ratio of rock powder for the improvement of expansive soil is about 24%.