During the long-term operation of tunnels, surrounding rock undergoes creep effects under environmental loads, resulting in changes in the aging evolution model of stress and deformation in surrounding rock and lining, which affects the long-term operational safety of the tunnel. Therefore, using the model test device for time-dependent characteristics of stress and deformation of weak surrounding rock and lining structure in operational tunnels, taking into account the influence of tunnel burial depth and lateral pressure coefficient of surrounding rock, a model test on time-dependent characteristics of stress and deformation in weak surrounding rock and lining structure was conducted, and the stress and deformation time-varying curves at key locations of surrounding rock and lining were obtained. The time characteristics of surrounding rock stress, the contact force between surrounding rock and lining, internal force, and displacement of lining structure were analyzed. Research findings indicate that the stress of surrounding rock, the internal force and displacement of lining structure, and the contact force between surrounding rock and lining all increase and tend to be stable over time under constant load. This implies that the stress and deformation of the surrounding rock and lining structure exhibit time-dependent changes. With changes in burial depth and lateral pressure coefficient, significant variations are observed in the various indicators of stress and deformation in the surrounding rock and lining structure, indicating both time-dependent and long-term characteristics in terms of stress and deformation. The research results provide basic data support for the study of the time-dependent characteristics of stress and deformation between weak surrounding rock and lining structures in operational tunnels and can provide theoretical and technical guidance for the long-term service status discrimination and disaster prevention and control of operational tunnels.

The investigation of the seepage degradation behaviors and time-dependent evolution law of physical and mechanical properties for splitting grouting reinforced body (SGRB) is of scientific and engineering significance for the development of disaster prevention and control. The triaxial seepage tests and triaxial compression tests were conducted to investigate the effects of grout vein dip angle on the time-dependent evolution law of physical and mechanical properties, deformation characteristics, and seepage degradation behaviors. The characteristics of flaws within the SGRB specimens were also examined from a microscopic perspective based on the technology of industrial computed tomography. According to the test results, the seepage process of SGRB specimens exhibits obvious stage characteristics. The time-dependent evolution law of deformation, peak deviatoric stress, deformation modulus, and porosity of SGRB specimens is affected by the grout vein dip angle. The dry mass of lost particles is positively correlated with the experimental time. The evolution process of flaws and seepage channels within specimens with different grout vein dip angles at different cross-sectional positions shows significant differences. The seepage failure modes of SGRB specimens are mainly divided into soil-grout vein interface failure mode and soil seepage failure mode from a microscopic perspective.

To gain insight into the anisotropic mechanical properties and failure behavior of shale, the cracking behavior of shale under compression and tension was investigated experimentally from the macroscopic and microscopic perspectives. The uniaxial compression tests were first carried out, and the effects of bedding plane on the generation of microcracks were analyzed through the technology of nuclear magnetic resonance. Then, the Brazilian splitting and confocal laser scanning microscopy tests were performed, and the corresponding relation between the failure mode and the fracture surface morphology was discussed. The results reveal that the mechanical properties and failure modes of shale are affected significantly by the existence of bedding planes. The distribution characteristics of microflaw radius and porosity change significantly due to the action of uniaxial compression, and the highest porosity of newly-generated microcracks is that of the 0° specimen. The newly-generated microflaws in 0°, 30° and 90° specimens are mainly contributed by seepage microflaws, while those in 60° specimen are mainly contributed by capillary microflaws. In the Brazilian splitting test, the fracture surface morphology of the specimen is significantly affected by the bedding angle, and the fracture surface morphology of the specimen is closely related to the failure mode and mechanism.