The swelling behavior of rocks can be significantly affected by variations in moisture history, particularly through cyclic wetting and drying. The oedometer swelling test is widely utilized to assess the swelling characteristics of rock specimens. In this study, a comparison was made between conventional oedometer swelling tests and cyclic wetting and drying oedometer swelling tests on rock specimens. The objective was to evaluate the influence of cyclic wetting and drying on the resulting swelling curve. The slope of the swelling curve obtained from the cyclic test was more than double that of the conventional test. This comparison underscores the importance of accounting for cyclic wetting and drying conditions when assessing the swelling behavior of rocks and highlights the potential implications for long-term engineering projects involving rock structures.
When certain types of rock come into contact with water, they have the ability to absorb and retain water within their structure, resulting in an increase in volume. This phenomenon is commonly known as rock swelling.
Swelling rocks and swelling rock masses can have detrimental effects on the performance of foundations and the stability of underground excavations. When encountered in tunneling projects, swelling rocks can lead to perimeter convergence and cause damage to the support system of the tunnel.
Rock masses may undergo repeated fluctuations in water content due to changes in groundwater levels and evaporation, leading to continuous damage and weathering that affects its physical and mechanical properties. The disintegration of rock caused by wetting and drying cycles can increase water absorption and enhance swelling behavior. This phenomenon has been observed in various types of rock, as reported in studies by Diop et al. (2008), Hua et al. (2017), Jiang et al. (2022), Doostmohammadi et al. (2009), Vergara & Triantafyllidis (2015), and Selen et al. (2020).
The logarithmic equation that describes the relationship between swelling strain and swelling pressure, known as the swelling curve (Grob 1972), shows that swelling strain increases as pressure decreases. In this equation, the parameter K corresponds to a material constant and σ0 is the swelling pressure obtained under constricted deformation (maximum swelling pressure).
