Rock blasting during tunneling has shown that the rock failure in high in situ stress environments is different from that in low in situ stress conditions or with a shallow rock mass. In particular, the propagation direction of the main crack induced by blasting is greatly affected by the in situ stresses. In order to study the law of crack propagation in rock during blasting under the conditions of an initial in situ stress, a transparent material that conformed to the mechanical properties of hard rock was used to carry out a similar model rock blasting test, under a unidirectional load. The results show that initial stress has a great influence on the propagation number, length, and direction of the main radial cracks. The specific performances were as follows: under the action of an equal confining pressure load, the longest main radial crack in the model specimen propagated along the diagonal direction, and the number and length of the main radial cracks propagated decreased with the gradual increase of confining pressure stress; in addition, the diameter of the circumferential cracks also decreased with the increase of stress, and there was a negative correlation between them. In view of the phenomenon where the longest main radial crack propagated along the diagonal direction in the model test, a mechanical model was established in this study to explain this process. This is of practical significance for understanding the mechanism of rock fracture when blasting with high in situ stresses.

The diversion tunnel is frequently subjected to cyclic dynamic loads during blasting and mechanical excavation. To explore the theory and mechanism of cyclic dynamic mechanical damage for granite in a diversion tunnel under cyclic loading-unloading, the incremental cyclic loading-unloading test and numerical simulation were conducted on granite samples from the diversion tunnel. According to the mechanical and deformation characteristics of rock samples in the process of cyclic loading-unloading, the stress-strain normalization theory evolution model based on viscoelastoplasticity was established, and the cyclic dynamic damage evolution mechanism of rock samples was revealed. The evolution characteristics of stress-strain curves of rock samples under cyclic loading-unloading were effectively described, and the loading-unloading two-stage constitutive equation of rock samples under cyclic loading-unloading was established. The energy and damage evolution mechanism of the final full stress-strain curve and the influence mechanism of shrinkage and expansion of rock particles on the mechanical properties of granite were discussed.

The dynamic compressive test of rubber cement mortar (RCM) under two different curing humidity levels (the relative humidity was 95% and 50%, respectively) was carried out by using a split Hopkinson pressure bar (SHPB) device, and the dynamic mechanics and damage evolution characteristics of RCM were studied. The results show that the impact resistance of cement mortar is obviously improved by adding rubber particles and is decreased by reducing the curing humidity. The stress-strain curve of the RCM has a transverse fluctuation in the top region, which reflects the excellent ductility and toughness of the RCM. Both dynamic peak stress and dynamic increase factor (DIF) have a linear positive correlation with strain rates, and the DIF is reduced due to the decrease in curing humidity. A damage analysis was carried out, and the reduction of curing humidity and the incorporation of rubber particles increased the damage variable $D$ and significantly changed the dynamic damage evolution process of the cement mortar. Finally, the blasting disturbance and the surrounding rock stability were analyzed along with the material properties and underground engineering issues. Therefore, this engineering application analysis demonstrated that the rubber cement-based materials have a prospective application.

In order to obtain the relationship between fractal dimension and energy dissipation of rock-like materials under initial stress state, a variable cross-section split Hopkinson pressure bar (SHPB) test system with active confining pressure loading device was used to carry out impact compression and splitting tests on cemented sand specimens. The impact test results show that (1) the prediction value on the fragmentation degree of cemented sand specimens by using the fractal model is basically consistent with the screening results of actual test, which verifies the applicability of the fractal calculation model given in this study; (2) the more the fracture energy dissipated in the crushing process of cemented sand specimens, the more serious the fragmentation degree is, and accordingly the larger the fractal dimension is, that is, the fracture energy is positively correlated with the fractal dimension; (3) there is an exponential relationship between the fractal dimension and energy dissipation of cemented sand specimens under initial stress, which is so different from that under no initial stress. The experimental results in this study can be used to modify the fractal damage model for rock blasting considering the initial stress.