No.22 October 1997

Study on the Detonation Properties of Explosives in Bore Hole and Precise Controlled Blasting

Summary

The blasting to break the rock and structure using the energy of explosives is one of the important operation for mining and civil engineering. The consumption of explosives is in the tendency which increases still today when the excavating work with machine such as tunnel ba11ing machine and the loading headers gains in popular. The reason of this is that the blasting have a useful characteristic that the destructive forces is larger in application to various rocks and working environment. The blasting demolition which uses explosives to demolish the structure in the urban area become major interest. However the blasting work in tile urban area is not put to practical use from the problem of the noise, the vibration and ny rock caused by blasting. Therefore, the development of the blasting method is need. As the blasting accident is generated still, it is important to know the detonation properties of explosives in bore hole to prevent the blasting accident.

It is important for effective and safety control blasting to know the detonation properties of explosives in bore hole. It is impossible to carry out the precise blasting using delay detonator that control the stress wave generated by explosives. So it is need to develop the precise control blasting system which can control the initiation time within 1µs.

In this report the detonation properties of explosives in bore hole is clarified and developed the precise control blasting system and applied to exploration of rock with elastic wave. This report consist of seven chapters as follows.

Chapter 1 is the problems of the research is pointed out and the meaning and the purpose of this report are described.

In the chapter 2 first time the evaluation method of detonation properties of explosives in bore hole using the resistance probe and lead plate was established. The detonation properties of explosives in bore hole was studied in open and confirmed condition in bore hole using confirmed detonation test equipment. It was pointed out that it was clarified that the sympathetic detonation of explosives was obstructed by the coal and rock powder's existing as a factor to obstruct the sympathetic detonation of explosives and the cleaning in the bore hole and tamping were important.

In the chapter 3 the delay blasting in practical plural bore hole was assumed and detonation properties of explosives in the state of pressurizing was studied. nat is, the pressure which jointed explosives in bore hole was examined about the kind of a static pressurizing with the compressed nitrogen gas and a dynamic pressurizing with the detonating fuse. It was clear that the water-gel explosives with the aluminum for sensitizer was influenced easily most in the state of a static pressurizing and emulsion explosives is not easily most. The reason for this is that pressurizing includes a strong glass micro balloon as a sensitizer in emulsion explosives. Moreover, it was clear that the strength and detonation delay time of pressurizing gave the influence of detonation properties in the state of dynamic pressurizing. In addition, the dead pressure of water-gel explosives recovered over several mil second later and detonated.

In the chapter 4 the safety of the direct and indirect initiation method was studied. First of all, the blast vibration by the difference of the initiation method was examined and remarkable difference did not obtained. However, the indirect initiation method showed the blasting effect and the state of the face was excellent from a numerical simulation. Next, safety to the inflammable gas of the indirect initiation method was examined. Safety for inflammable gas was confirmed from the experiment with mortar mortar and grounds of the introduction into the coal mine were shown.

In the chapter 5 the initiation method by which the initiation time of the precise detonator was controlled in precision was established as a basic research for precise initiation method. Moreover, the vibration and fly rock control by this method were examined. A precise detonation machine and a precise detonator were developed and the precision was verified from the observation result with the high-speed camera. In the precise detonation system can control the initiation time from 1µs to l0s by the precision of 1µs. This is usually 1,000 times precision compared with the instantaneous electric detonator. It was confirmed to be able to examine the smooth blasting by the precise detonation system from the model experiment by the acrylic resin plate and mortar block and control the progress of the crack by interfering with the stress wave. It was also shown to be able to control the vibration and the fly rock from the model experiment by the acrylic resin plate and mortal block and numerical simulation. In addition, the flying characteristics and dispersion of the generated fly rock were elucidated from the blasting experiment on the reinforced concrete pillar which was the main collapse element of the city construction and the technical indication was given to the establishment of blasting method by the precise initiation system.

In the chapter 6 application to the seismic prospecting was examined as an example of applying the developed precise initiation system. The improvement of the points where the initiation precision was insufficient in the old seismic tomography was aimed. It was confirmed the precision become tens of times from analytical results by the field experiment. Moreover, the measurement is also easy and apply to practical use.

In the chapter 7 the results of obtaining with this report was summarized and the view in the future was described.