Comparative study on bearing mechanism and design parameters of confined concrete arch joints in deep soft rock roadway

Square confined concrete arch is increasingly used in deep soft rock roadway support because of its advantages of high strength and construction convenience.However,the design of confined concrete arch in underground engineering still remains in experience-based method and lacks quantitative analysis.As a connecting component between arch sections,the connection joints have an important influence on the internal force distribution and failure mechanism of support arch.Therefore,a reasonable design of arch joints is the premise of rational support design.Taking Liangjia Coal Mine,a typical deep soft rock mine in China,as research background,this paper fully compared the most widely used joint types of confined concrete arch as analytical objects:flange joints and casing joints.The main failure modes of these two kinds of joints under bending moment are defined.Laboratory and numerical tests are carried out to study the mechanical characteristics of joints.Based on the M-θ curve,the influence law of different design parameters is analyzed,and the design principles of joints are proposed.The research results could provide a theoretical basis for the design and application of confined concrete arch in related projects.