Theoretical study of bearing capacity calculation model for multi-segment confined concrete arch and design method in underground engineering

With the continuous development of underground engineering to the deep, complex geologic conditions such as high stress, extremely soft rock and fault fracture zone usually occurred in the construction process. The accurate calculation of confined concrete arch bearing capacity is the key to support design. At present, the theoretical value of the bearing capacity for the confined concrete arch is oppositely deduced according to the axial compression bearing capacity of basic component, and the bending moment effect of surrounding rock on arch is neglected. It does not consider the structural characteristics of inconsistent stiffness between the arch joints and segments. To obtain accurate calculation results, a theoretical calculation model of arch with arbitrary section numbers and unequal stiffness is established. By the full-scale laboratory and numerical tests, the deformation and failure characteristics of the confined concrete arch are analyzed. The results show that the vault position, bottom position and waist position are the key failure positions of the arch. The difference rates of theoretical calculation results compared with laboratory test results of ultimate bearing capacity are within 5%, which verifies the rationality and correctness of theoretical calculation model. On the basis of the above research, the support design method of confined concrete arch is proposed. The support parameters of on-site confined concrete arch are designed based on the engineering background of the typical deep mine with high stress—Liangjia coal mine located in China. The surrounding rock of the roadway is stably controlled.