Analysis of cyclic swelling of mudrocks

Mudrocks are very common rocks that when in contact with water can present considerable volume change and breakdown. The many factors interacting in the swelling phenomenon complicated the approach required to carry out the present work, which focuses on the impact of cyclic wetting and drying on swelling behavior of mudrocks. The samples studied are Cretaceous Age mudrocks (Terres Noires) from the French Alps, Toarcien mudrocks from the Banassac area (south of France), and Tertiary Age mudrocks from the French Central Massif (Marnes of Limagne). Analyses of grain-size distribution, mineralogical composition, pore-size distribution, and cation-exchange capacity were made. Scanning electron microscopy (SEM) registered the condition of samples before and after free and pressure swelling tests. The results showed the importance of rock texture and structure in addition to mineralogical composition. Cyclic wetting and drying of the samples demonstrated the different mudrock behaviors that could be determined with the coefficient proposed in this work.