Abstract:  A case study is conducted on the entrance section of a highspeed railway tunnel blasting project to address the challenges expected during excavation by rock blasting, and multiple groups of hydrostatic and nonhydrostatic stress loading conditions are set up to numerically simulate the wedge cutting blasting process and analyze the influence of different ground stress conditions on the expansion of rockburst cracks. The rationality of the model parameters is validated by comparison with the measured data. The results reveal that: (1) The compressive stress component of the stress wave superposition area is higher because the section being cut is inclined to the free surface, resulting in greater compressive damage to the rock inside the holes. At the same time, cracks are generated at a distance from the hole, and part of the rock between the blast holes that is near the free surface suffers tensile damage, which is conducive to the blasting of the subsequent auxiliary holes. (2) Under hydrostatic stress conditions, the evolution of rock blasting damage is inhibited with an increase in ground stress, while under nonhydrostatic ground stress conditions, the extent of the damaged region expands along the direction of the maximum principal stress, and the difference between the lengths of the horizontal and vertical crack of the groove cavity becomes more pronounced with a decrease in the lateral pressure coefficient. (3) When the hydrostatic stress is around 20 MPa and the wedge cut angle is about 60°, the effect of rock blasting is less affected by the ground stress.

Key words: highspeed railway tunnel, wedge cut, damage evolution, ground stress, numerical simulation