Mechanical characteristics and damage model for rock-like specimen with two parallel grout-filled cracks

Abstract

To investigate the mechanical properties of rock-like specimens with two parallel cracks filled with grout, uniaxial compression tests in combination with digital image correlation (DIC) and acoustic emission (AE) techniques have been performed on grout-filled cracked specimens with different rock bridge dip angles β. Results indicated that with the increase of β, the uniaxial compression strength, cumulated AE count, AE energy, as well as shear crack proportion initially decreases and subsequently increases. The overall AE b-value and the DIC-based maximum principal strain initially increases and subsequently decreases as β increases. The failure mode also varies from tensile to mixed tensile-shear mode. Furthermore, a particle flow code (PFC) model, which considers the grout filling, grout-rock interface, and rock, has been proposed. Numerical results showed that the range of microcracks inclination angle first decrease from 70°−100° to 70°–90° and then increases to 70°–110°. Besides, existence of grout filling and changes of bridge angle leads to significant difference in PFC particle displacement, which can cause the changed of crack initiation positions and failure modes. Finally, a damage model considering stress intensity factor for the grout-filled specimen was established. Both of pre-crack damage and loading damage were considered in this model, and a damage repair factor was proposed to describe effect of grout filling. The results showed that grouting could can effectively suppress stress concentration caused by pre-existing crack, thereby changes the strength of cracked specimen.