Study On The Mechanism And Application Of Air-Decking Blasting

There are quite a lot of reports about air-decking technique at home and abroad lately which report the good performance. It can not only overcome the base and break rock, but also can lower the vibration and minish the destroying to the construction foundation. These practices have provided valuable experience and profitable exploration for future research. All researches indicate that the similar effect can be obtained in blasting with air-decking technique as opposed to general charging. But it can reduce the work of charge and the amount of igniter materials, so that it can improve the work efficiency and reduce the cost. Actual investigation proves that the research of the blasting method still rests on the aspects of examination and exertion in local area and is not mature which is on the stage of exploration. It has not yet formed a suit of integrated theory and also has no systemic and relatively perfect data which has just done some trials and accumulated some experience. In the popularized process of air-decking technique in China, it's an important task to study the mechanism of air-decking and to determine the air-decking ratio from theory. It has high technical value and wide potential foreground of the engineering application. On the basis of the previous work, exerting the theory of one-dimensional nonstable flow, the action of the detonation waves to the borehole is studied in this thiese and some results are obtained which are listed in following:The mechanism of air-decking technique is analyzed. According to the analysis of the expanding process of shock waves and detonation products and the interaction of them with the bottom of the borehole and the end of the stemming, the time history and space distribution of one dimension pressure in borehole are determined. So the mechanism of the air-decking technique is quantitative analyzed from theory.The air-decking ratio in bench blasting is quantitative determined. In order to assure that the near area of borehole is crushed to pieces by the high pressure and the far area has the good blasting effect by the continuous loading and unloading of the pressure wave and make good use of blasting energy, according to analyze the time history of stress in borehole when the air-decking locates at different place and the detonation way is different and numerical analysis, the following achievements are obtained. The air layer locates at the top is better than that locates at middle and bottom. Detonation at bottom is better than detonation at top. Based on the theoretical analysis, the advantage of air-decking demolish can be used efficiently only if the air-decking ratio varies from 0.3 to 0.42 in bench blasting.The air-decking ratio in pre-split blasting and smooth blasting is quantitative determined. In pre-split blasting and smooth blasting, in order to form cracks between the boreholes but not destroy the bore walls by high compressive stress in borehole, according to analyze the time history of stress in borehole when the air-decking locates at different place and the detonation way is different and numerical analysis, the following achievements are obtained. The air layer locates at the top is better than that locates at middle and bottom. Detonation at top is better than detonation at bottom. Based on the theoretical analysis, the advantage of air-decking demolish can be used efficiently only if the air-decking ratio varies from 0.6 to 0.8 in pre-split blasting and smooth blasting.The experiments on site indicate that the air-decking ratio achieved by theoretical derivation is not only the same with the technique of large diameter borehole blasting in mining, but also applicable to small diameter borehole blasting which is popular in China.