|
Abstract A blasting-induced damage model on account of initial damage was suggested based on the current theory of blasting induced damage on rock. The relationships among the initial damage，acoustic wave velocity，elastic modulus and threshold value of blasting induced damage were also presented. The effects of blasting induced damage and the main influencing factors under the blasting excavation of protective layer of rock bench for anchoring crane girder of the main underground powerhouse of a lager hydropower station at Xiluodu were analysed and the formulas of blasting parameters were suggested. The blasting parameters were provided owing to two engineering classifications of rock mass with different initial damages mainly located in the main underground powerhouse. The blasting tests simulating the excavation of protective layer of rock bench，the blasting vibration velocity tests and the borehole acoustic wave tests were carried out in the field，and then，the rationality of blasting parameters was proved and some supplements were added to improve the design of blasting parameters. The results showed that the initial damage of rock mass should be taken into account for the calculation of blasting parameters. The blast-hole concentration coefficient from the study was smaller than that from common smooth blasting design for the blasting excavation of protective layer of rock bench. When the initial damage of rock mass increased，the coefficient of non-coupling charge should be increased and the concentration coefficient of blast-holes for smooth blasting should be reduced. For the excavation of protective layer of rock bench，the control of both the blasting-influenced depth and the blasting seismic effects meets the requirements suggested by the hydropower station，thus，the design of blasting parameters is of rationality. The research results can provide references for similar projects.
|
|
|
|
|
|
2016, Vol. 35 
