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 mesoscopic 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.

Soft rock engineering is involved in many important engineering fields such as mining, hydraulic engineering, transportation and national defense. With the increase of mining depth and the development of tunnel engineering, a large number of tunnels and roadways need to pass through soft rock formations, in which the problems such as high geostress and broken and weak surrounding rocks are prominent. Large deformation disasters of soft rocks pose serious threats to engineering safety and cause enormeous economic losses. In this paper, the research progress on soft rock support in China is first reviewed, and the research status quo of technology for soft rock control for large deformation hazards is summarized in the following aspects: (1) passive support methods represented by improved rigid support, retractable support and compound lining; (2) reinforced active support technology using high-strength bolts and cables; (3) soft rock modification technology using grouting; (4) soft rock reinforcement with pressure relief as the core idea; and (5) compound support methods. Furthermore, the development of different supporting technologies and methods is elaborated, and the applicable conditions, advantages and disadvantages of different supporting methods are analyzed. It is usually difficult to meet the demand of large deformation control of soft rock relying on a single support method. Therefore, it is urgent to solve the problems of the prevention and control of large deformation disaster of soft rock to realize the efficient collaborative control among different supporting measures and achieve the real-time accurate monitoring of deformation and stress fields. Finally, based on the above research results, the development tendency of support technology for soft rock with large deformation hazards is prospected and the countermeasures are proposed.