Cyclic fatigue responses of double fissure-contained marble: Insights from mechanical responses, energy conversion and hysteresis characteristics

Abstract

The intermittent fissures are widely distributed in rock mass, rock bridge segment among the fissures are crucial to the mechanical properties and stability of rock mass. The static mechanical behaviors of fissure-contained rock were well understood, yet the fatigue mechanical properties were poorly investigated. This work aims to reveal the influence of rock bridge length on rock mechanical responses, energy dissipation and hysteresis characteristics in lab-scale. Marble samples with rock bridge length (RBL) of 10, 20, 30, and 40 mm were prefabricated as parallel pattern, and they are subjected to multi-level fatigue loading paths. Testing results show that the rock bridge between the fissures resists rock deformation and the terminal volumetric strain decreases with increasing RBL. In addition, the hysteresis energy density and damage evolution are influenced by the rock bridge length. The strain energy density development aligns with deformation pattern results. Deterioration in the rock bridge structure causes reduced capacity and higher energy consumption. More energy is required to drive damage progression and crack connectivity in rocks with a larger RBL. Ultimately, two hysteresis indices are introduced to characterize fatigue damage evolution. These indices exhibit nearly opposing trends throughout the loading process. It is proposed that extending the rock bridge length results in a roughly linear trend for both hysteresis indices.