Investigation of safety control for rock blasting excavation under cold condition
摘要
The safety control of blasting vibration under complex condition is the key problem of excavation. The rock mass is frozen under the cold condition, which induces the change of mechanical performance and wave impedance properties, and affects the blasting vibration attenuation characteristics. Firstly, the comparitive experiments are implemented to study the mechanical performance under different conditions. The results reveal that the increase of the elasticity modulus can reach as much as 30%. Based on the test results of the reconstruction project of Fengman Hydropower Station, the characteristics of blasting vibration attenuation for summer and winter are compared. The results reveal that a cut-off point about scaled distance exists, and the magnitude of the relationship changes at the cut-off point. The effect of cold depth is investigated, and a mathematical description for the maximum charge weight versus frozen depth is proposed. Finally, the effect of blasting vibration control standard is studied under cold condition from the angle of spectral characteristics of stress wave and the ultimate strength of the structure. The research results may provide the reference for the blasting safety control in the north cold excavation regions.