Research on Deformation of Surrounding Rock by Linear Monitoring Technology in Large Underground Cavity with High Geostress

Based on the monitoring data of INCREX Mobile Extensometer implemented on the dome and engineering geological investigation in large underground cavity, the deformation characteristics of surrounding rock of dome in the cylindrical cavern and the middle wall of the long corridor-shaped underground cavern are discussed, as well as the development of relaxation circle. The spatial differentiation and evolution law of deformation in the cylindrical cavern dome are analyzed. The range and evolution characteristics of relaxation zone of mid-partition in large underground caverns are clarified. The results show that: (1) The structural plane has little influence on the deformation magnitude of the surrounding rock of the cylindrical cavern dome (within 5 mm), and the deformation law of the joint rock in the dome is similar to that of the grade III surrounding rock. The deformation of the surrounding rock mainly occurs in the construction period near the excavation face, and the influence range is limited to the normal dome. (2) The air in the measuring micrometer borehole is connected with the air in the cavern, and the measured value has a periodic variation. (3) The range of relaxation zone is proportional to the degree of stress concentration, and the maximal depth of relaxation zone is about 1/3 of the excavation height. The development of relaxation zone is mainly concentrated in the excavation stage, and there is basically no expansion after the cavity is formed. The research results can provide reference for the optimization and stability evaluation of the supporting structure of deep buried caverns under high geostress.