Consolidated undrained shearing response of hydrophobic sands

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Civil Engineering, Turkey

Approval Date: 2018




The geotechnical properties of hydrophilic (wettable) sands have been widely discussed in the literature. However, sands may gain hydrophobic (non-wettable) property after certain processes. Available studies regarding the response of hydrophobic sands mostly focused on its environmental and hydrological aspects. The current state of knowledge about the geotechnical aspects of hydrophobic sands is quite limited and consists of the results of a limited number of direct shear tests. To close this gap, a comparative laboratory testing program consisting of 18 static strain-controlled consolidated undrained triaxial shear tests was designed. Tests were performed on fully saturated hydrophilic and hydrophobic reconstituted Kızılırmak sand samples of different relative densities with pore water measurements. Additionally, soil classification tests including specific gravity , minimum void ratio and maximum void ratio determination and sieve analysis were performed. Hydrophobic samples were prepared by using varying amounts of WD-40 lubricant. The effects of hydrophobic agent was examined by comparing the stress – excess pore water pressure - strain responses of hydrophobic sand samples with those of conventional (hydrophilic) sand samples. Test results revealed that addition of hydrophobic agent increases the dilatancy of sands at low confining stresses (~100kPa) by decreasing the excess pore water pressure generation. At higher confining stresses (~400kPa) this effect is less pronounced. Moreover, the addition of hydrophobic agent does not significantly and systematically change the shear strength of sand samples independent of their initial relative density and confining stress levels.