'Cohesive Soil:' A Dangerous Oxymoron

by Carlos Santamarina
Year: 1997


Santamarina, J. C. (1997). "'Cohesive Soil:' A Dangerous Oxymoron." The Electronic Journal of Geotechnical Engineering, Vol. August


​Oxymorons or self-contradictions are often used in our daily lives. An oxymoron is also said to be "a wittily paradoxical turn of phrase which appeals to unconscious responses instead of rational examinations “(Robertson, 1997). Consider for example, “organized chaos” and “incomplete solution”. Oxymorons often express a wish or an assumption, yet, they may also capture a misconception. The geotechnical literature is not exempt from oxymorons. For example, analytical solutions for interparticle contact clearly show that soils and all particulate materials are inherently non-linear -Hertz theory- and non-elastic -Mindlin’s theory (See Richart, Hall and Woods, 1970; Cascante and Santamarina, 1996). Yet, “linearelastic soil behavior” is a common expression. In most cases it refers to the model selected to interpret test results or to the assumption made in the design of geosystems subjected to small strains. For many reasons, linear elasticity has proven quite useful (insensitivity of the induced field of stress to material parameters and difficulty in gathering parameters for more sophisticated and complex constitutive models). The purpose of this electronic note is to argue against the use of “cohesive soil”, probably the most pervasive oxymoron in the geotechnical field today. Indeed, the terms “cohesive soil” and “cohesionless soil” are almost equivalent to soil classification. The use of these terms creates a confusing framework for teaching purposes, and pre-sets the engineering mind with the wrong model of behavior. Ultimately, it leads to less reliable geotechnical systems when fine-grained soils are involved.