Determination of static and dynamic properties of problematic soils stabilized by silica fume and comparative analysis

Soils classified as problematic, such as dispersive and swelling clays, are considered a natural hazard even though they do not directly threaten life compared to other natural disasters. Problematic soils encountered during engineering projects such as airports, highways, and railways may not possess the desired engineering properties. Various studies have been conducted to improve these problematic clay soils, which are found in many countries and cause significant damage, using different additives. Following stabilization with silica fume, the swelling and dispersive properties of the soils improve, and their strength characteristics and workability are significantly enhanced. In this thesis study, necessary clay samples were obtained from a designated site, and soil identification tests were conducted. Soil-silica fume samples prepared at different ratios (0%, 5%, 10%, 15%, 20%, 25%, and 30%) were compacted under specified compaction conditions, and swelling and dispersibility tests were performed to evaluate the additive's performance in detail. Unconsolidated-undrained (UU) tests, resonant column tests, dynamic triaxial tests, and bender element tests were conducted on samples subjected to different confining pressures (20, 40, and 60 kPa) and curing times (1 day, 7 days, and 28 days) to examine the strength parameters of soil samples under static and dynamic loads, such as cohesion (c), internal friction angle (φ), damping ratio (D), shear modulus (G), modulus reduction ratio (G/Gmax), and shear wave velocity relationships. The changes in the strength characteristics of the stabilized soil pre- and post-cyclic loading were determined in two stages by performing UU tests on the samples subjected to dynamic loading. The results indicate that the dispersive and swelling properties of the soil sample improved with the addition of silica fume (SF). This improvement increased with curing time, and the static and dynamic strength properties developed depending on the silica fume content.