Crack initiation behavior in grouted fractured mudstone: Insights from laboratory tests and DEM simulation

Abstract

Fractured mudstone is prone to structural failure due to weak cementation, low strength, and fissured texture. This study investigated the mechanical behavior and crack evolution of grouted fractured mudstone using uniaxial compression test (UCT), direct shear test (DST), and discrete element method (DEM) simulation. Results indicated that silica-sol grouted specimens under UCT exhibited a higher compressive strength and ductility, with cracks deviating from both sides of the prefabricated fracture, whereas a concentrated and stable shear band was detected in the cement-grouted specimen under the DST, thus improving resistance to the slippage on the interface. Crack evolution was strongly governed by the interaction between fracture inclination and stress state, with a larger inclination angle across the failure zone of the tested specimens. It was revealed from DEM analysis that the rupture and redistribution of strong-force chains during the late loading stage led to the stress concentration and crack penetration. Although an increase in the grouting thickness improved a load-bearing capacity, it also intensified the crack propagation, especially under the UCT. These findings deepen the micromechanical understanding of crack initiation and propagation, providing a theoretical basis for modeling and mitigating failure in grouted fractured rock.