The Key Technology Research And Application About The Large Aperture Small Steps Loose Blasting

As the protective layer due to closing the non blasting area and the thickness is small, generally using the shallow hole blasting method to excavate. But the number of drill is much more and the workload is big. It cannot guarantee the smooth realization of the time limit for a project. Due to the bigger blast hole diameter, more single hole charge and can afford a larger area, so using a large aperture small stair blasting method to excavate the protection layer plays a positive role in promoting the duration and speeding up the work. For the more single hole charge,explosion would cause the unnecessary damage to the reserved rock. Solving the damage of the small steps and the large aperture loose blasting at the bottom of the hole of rock is the key to extend the application of large aperture small bench loosening blasting technology. In this paper, basing on a nuclear power station excavation project in Shandong, according to the actual requirement of engineering application, the author studied and optimized the charge structure of the large aperture small bench loosening blasting. He raises in the protection layer excavation, applying the hole bottom air interval charge structure to the large aperture small stair loosen blasting. One hand it can make a blasting excavation volume increased, on the other hand can play a protective role to retain the stability of rock mass.The thesis mainly through theoretical analysis, numerical calculation, numerical simulation and field experiment to investigate the large aperture and small stair loosen blasting with the hole bottom air interval charge structure, the primary coverage are as below:(1) Through the theoretical analysis, it has been clear about the hole bottom air interval charge mechanism to the rock surrounding hole; through numerical calculation, get the calculation method of hole bottom rock damage range, and calculated under different conditions of hole bottom rock damage range.(2) By using the ANSYS/LS-DYNA dynamic finite element analysis software to make the numerical simulation, comparing the effective stress on the hole bottom rock with the continuous coupling charging and hole bottom air interval charge,it proves that the latter can protect the bottom hole rock stability in a certain extent; In accordance with the theoretical calculation of large aperture and small stair loosen blasting parameters and related parameters of hole bottom air column to build model, simulation of the bottom hole rock damage scope shows a little difference with the theoretical calculation.It proves the theoretical formula for the hole bottom rock damage range is reasonable.(3) In a Shandong nuclear power plant project department, the auther made the scene experiment according to the blasting parameters by theoretical calculation and numerical simulation. The experimental results prove that the large aperture small stair loosen blasting to excavate the rock of protection layer can speed up the progress of the project, and the use of hole bottom air interval not coupled charge can protect the infrastructure stabilization very well.