As a man-made engineering hazard, it is widely accepted that the rockbursts are the result of energy release. Previous studies have examined the unloading of in-situ stress resulting from deep tunnel excavation as a quasi-static process but the transient stress variation during excavation has received less attention. This research discusses rockbursts that happened during the construction of a diversion tunnel at Jinping II hydropower station. The brittle-ductile-plastic (BDP) transition property of Jinping marble was numerically described by the Hoek-Brown strength criterion, and the dynamic energy release process derived from the transient unloading of in-situ stress was studied using an index, local energy release rate. Studies have shown that, due to transient unloading, the strain energy of the surrounding rock mass goes through a dynamic process of decreasing at first, increasing second, then reducing before finally stabilizing. The first decrease of strain energy results from elastic unloading waves and does not cause brittle failure in rock masses, which is consistent with the elastic condition but the secondary reduction of strain energy is because the accumulated strain energy in rock masses exceeds the storage limit, which will inevitably trigger the brittle failure in the rock mass. Thus, the shorter the distance to the tunnel wall the bigger and more intense the energy release. Finally, a relationship between the average value of the local energy release rate and the rockburst intensity was established to assess the risk of rockburst induced by the blasting excavation of a deep tunnel.

During the process of blasting excavation of deep rock masses under high in situ stress, energy produced by the explosive and the strain energy released by rock mass excavation constitute the energy source of vibration. However, in traditional Sadov’s empirical formula, the energy produced by explosive explosion is only considered which makes the error higher when it is used to predict the blasting-induced vibration peak under the condition of high in situ stress. In this study, energy transformation and distribution mechanisms caused by excavation of deep rock masses were analyzed at first. Then, a prediction model of vibration peak based on the principle of energy balance was established by dimension analysis. Finally, the proposed model was trained and tested with the vibration data monitored during the blasting excavation of deep buried tunnel in Jinping II hydropower station. The result shows that compared with the traditional prediction model, the proposed model has higher fitting correlation coefficient and lower root-mean-square error, which can be better applied to the prediction of vibration induced by blasting excavation of deep rock masses under high in situ stress.

Fluid–structure interaction (FSI) involving free-surface flows remains challenging due to complex free-surface evolution, transient hydrodynamic pressure transfer, and structural deformation. This study develops a direct coupling framework between smoothed particle hydrodynamics (SPH) and non-ordinary state-based peridynamics (NOSBPD) to improve the accuracy, stability, and efficiency of free-surface FSI simulations. In the proposed framework, structural particles are directly treated as SPH boundary particles, and the FSI force is obtained through pressure interpolation and Newton's third law, avoiding additional virtual-particle generation. Flexible and independent spatial discretizations are allowed for the fluid and solid domains, so that their resolutions can be adjusted separately without simultaneous refinement of both domains. NOSBPD is used to describe structural deformation and directly calculate stress and strain fields. A condition-number-assisted particle shifting technique is introduced to improve the efficiency and stability of free-surface particle identification and particle distribution correction, reducing local pressure oscillations near the free surface and fluid–structure interface. The solver is accelerated using Taichi-based graphics processing unit computing with an optimized linked-list neighbor search, achieving more than 3 orders of magnitude speedup over single-core central processing unit computation. Benchmark tests show normalized root mean square error within 1% for structural deformation and below 3.5% for free-surface flow quantities. Compared with representative particle-based FSI results, the proposed model produces smoother pressure fields and more accurate structural displacement predictions. The last application simulation further demonstrates its capability to stably capture strong free-surface loading, large deformation of complex free-surface FSI simulations.