Influence of Fine Materials on the Mechanical Behaviour of Treated Gypseous Soils under Unconfined Compression

Abstract

Gypsum soils in Iraq suffer from collapse problems and poor stability when exposed to moisture, leading to subsidence and cracking of structures over time. This challenge is one of the most prominent geotechnical problems facing infrastructure projects in areas where these soils are common. The objective of this effort is to study the unconfined compression strength of gypseous soil by using three distinct stabilizer materials (fly ash = 8%, silica fume = 4%, and nano-silica fume = 2%), as well as fine particles of 10, 20, 30, and 40%. This investigation employed a soil sample that contained 53% gypsum.  This sample was taken between 0.5 and 1 meters below the surface of the natural ground and was donated by Tikrit University. To evaluate the strength characteristics of the studied soils, the Unconfined Compressive Strength (UCS) test was conducted on both natural gypseous soil samples and those treated with different additives. The main results show that dual treatment of additive materials and fine particles provides an effective solution to improve the compressive strength of gypseous soil, with an optimum fine particles ratio achieving maximum strength. Nano-silica fume-treated gypseous soil with 10% of fine particles achieved approximately 93% unconfined enhancement ratio, while silica fume and fly ash-treated gypseous soil with 20% of fine particles achieved approximately 82 and 73% unconfined enhancement ratio respectively.