Impacts of Void Existence on Mechanical Behavior of Tuff-like Lithophysal Material

In the current literature, the existence of lithophysae can cause a substantial change in the mechanical properties of tuff rock. However, since the shapes and distributions of the lithophysae are typically irregular and random, exploring the influence of lithophysae existence on the engineering behavior of lithophysae-rich tuff rock using the actual samples is very challenging. Besides, it is almost impossible to control the geometry of the lithophysae in the actual samples. Accordingly, in an attempt to explore the influence of void porosity and geometry on the mechanical behavior of tuff rocks, solid cubes as well as porous cubes with voids having different geometries were made of tuff-like material, Hydro-StoneTB^®, and tested under uniaxial compression. The Hydro-StoneTB^® was chosen because it resembled the tuff rocks in regards to strength and deformation under uniaxial stresses. The results showed that void geometry along with void porosity has a significant impact on the mechanical behavior of tuff-like lithophysal material. However, the mechanical behavior of the tuff-like lithophysal material mainly depends on the void porosity. The compressive strength values decreased with increased specimen void porosity. The strength/void porosity relationship is essentially exponential over the 6–20% void porosity range. The percent change in uniaxial compressive strength from the solid cube value is roughly 59, 72, and 82% at 6, 13, and 19.5% void porosity, respectively. Additionally, considering the smallest bridge distance could improve the description of the influences of the void geometry on the mechanical properties of the tuff -like lithophysal material. Furthermore, for the void porosity ranging from 6 to 20%, the crack patterns of the Hydro-StoneTB^® porous cubes showed that the axial splittings (tension failures) are the dominant failure modes. However, based on the void alignments and bridge distances, shear failures can occur.