Experimental investigation of the mechanical and permeability characteristics of volcanic breccia

In this paper, a series of experiments were conducted on typical volcanic breccia collected from the foundation of Baihetan Dam. Considering previous work, the mechanical behavior and permeability of the volcanic breccia were further investigated. The experimental results showed that the compressive strength and Young's modulus of the volcanic breccia decrease due to the presence of water. However, the Poisson's ratio of the wet specimens was higher than that of the dried specimens. The permeability evolution under triaxial compression was divided into 5 stages. The fluid pressure showed a great influence on the permeability of the volcanic breccia. The water weakening mechanism and the effect of fluid pressure on the permeability were discussed. The effect of water on the strength of volcanic breccia is influenced by both subcritical crack growth and calcite dissolution. Due to the pore pressure gradient and the water weakening effect, the change in permeability with volumetric strain varies greatly.