Fault zones

prevalent in deep geological strata

are commonly filled with fault gouge

rock debris and other fillings

significantly impacting the stability of rock masses. The shear mechanical properties of filled joints within fault fractures are intricate and influenced by various factors

including rock type and its mechanical properties

joint roughness

the mineral composition and mechanical characteristics of the fillings

and as well as interactions

such as groundwater. This paper reviews the research trajectory of the shear mechanical behavior of filled rock joints and provides a systematic summary of the current research status on their shear mechanical properties. The key issues and research progress of shear mechanical properties of filled rock joints are analyzed from the aspects of laboratory shear experiment

numerical simulation

shear strength criterion and constitutive model theory. The existing problems and development trends of different research methods were also analyzed. Presently

filling degree

mineral composition and mechanical properties of fillings are recognized as the most critical distinctions from unfilled rock joints. Additionally

factors like fluid interactions

normal stress

and joint roughness significantly affect the mechanical properties of filled joints. However

the shear strength theories developed through macroscopic phenomenological approaches struggle to find precise application in engineering practices. Future research will primarily tackle the shear mechanical properties of multi-scale rock joints with fillings

focusing on the meso-mechanisms of shear failure within filled joints

the development of shear criteria for different types of filled joints

and the corresponding numerical simulation models and mesoscopic parameter determinations. Investigating the complex behavior of multi-scale filled joints under multi-field coupling conditions is poised to become a leading and pressing research area.