Blasting Systems Research Articles

Abrasive blasting systems

Abrasive blasting systems

Blasting under Oslo : Smith, M; Carlson, R World TunnlgV2, N1, Feb 1989, P23–26

This article describes the construction experience of the Oslo tunnel, whose path cuts through several different geological formations. The tunnel is being excavated by conventional drill and blast techniques, despite the very strict vibration limits that have been specified. Purpose-designed charging and blasting techniques are being applied to keep ground vibration under control, and very sophisticated drill rigs are being used. The Norwegian geotechnical institute has coordinated the ground investigation, support design, and vibration monitoring on the tunnel. There have been extensive site investigations of the ground under the tunnel route, using seismic and acoustic measurements, core drilling and bedrock soundings. These surveys have provided excellent information about ground conditions above the tunnel and ahead of the face, and they have contributed to the design of the blasting and support systems. Numerical modelling has been used successfully to predict the effects of blasting on the pre-grouted sections of the tunnel. Nitro consult was engaged to design the blasting system to satisfy the requirements for extremely low ground vibrations. Experience indicates that this system can be applied to all tunnels under all conditions, providing a safe method of working and efficient use of explosives and detonators; ground vibrations can be restrained in a manner not previously considered possible. It was found in practice that all sections of the Oslo tunnel could be blasted full-face if required. (TRRL)

Seismic attenuation spectra in rock mass characterization; a case study in open‐pit mining

The application of engineering geophysics to the characterization of rock masses is exemplified through a case study of three phases of a research project into the design of efficient blasting systems in open‐pit mining. Seismic experiments are used before and after mine blasting to monitor the efficiency of explosions in terms of rock fragmentation. Spectral analysis of seismic signals, after they have been used to interrogate rock masses, is used to compute preblast and postblast attenuation and velocity parameters. The results show that fragmentation efficiency of a mine blast and fracture anisotropy of a rock mass can be quantified in terms of three‐dimensional (3-D) attenuation spectra and polar anisotropy diagrams. These seismic data are correlated with the blast design and the energy used by the excavating dragline machine to dig to rock mass. An overview of the seismic attenuation technique and instrumentation used in the project (phases I and II) is given. A case study from phase III highlights the scope and interpretation of the relationship between excavation parameters and seismically characterized blasting efficiency.