Geomechanical characterization of different lithofacies of the Cuitzeo ignimbrites

Volcanic rocks, especially ignimbrites exhibit complex mechanical behaviors due to their large variation in welding, porosity, textural and granulometrical characteristics. It is well known that the mechanical properties of rocks (mainly the uniaxial strength) are greatly controlled by variables such as grain and pore size and their shapes. In order to understand such variations the authors combined field and laboratory study of ignimbrites applying different analyses. The authors studied a well-exposed ignimbrite succession located at the southern edge of the Cuitzeo lake in Michoacán, México. The distribution of each ignimbrite lithofacies was spatially and temporally assigned, while only the most representatives ones were physical-mechanically characterized. Strength, deformation, as well as the failure behavior of selected lithofacies were directly related to micro-textural and granulometrical characteristics by a series of uniaxial and pre- and post-failure nondestructive analyses, including ultrasonic pulse velocity and X-ray image tomographies. Results were compared and evaluated allowing to explore the variation in the mechanical properties, directly related to the characteristics derived from their diagenesis.The results emphasized the importance of the physical-mechanical characterization of each ignimbrite lithofacies to construct conceptual and numerical models of different slope instabilities occurred in the zone, particularly along the Guadalajara-Mexico City highway.