Propagation Characteristic Of Water Shock In Underwater Borehole Blasting

Currently natural resources has become one of three factor for restricting human being development, however, in the situation of land resources gradually lessen, the eyes of each country in the world were trained on the underwater available resources in the sea, lakes, and harbors. The underwater blasting technology was an important means to underwater resources exploration and underwater construction, and its application was extended gradually from the military purpose and scattered underwater reef blasting to civilian industry, such as channel dredging, harbor, estuary exploitation and control, wrecked ship disintegration, transportation and water-power engineering construction and scientific study and test, etc. Following strengthen of safety and environmental awareness and improvement of drilling machines, the underwater borehole blasting become gradually the principle work means. Explosive in underwater borehole blasting was embedded in rock or hydro-structure, and the energy distribution, shock propagation and boundary condition influence were different from the underwater explosion and water surface explosion.On the basis of research results of underwater explosion fundamental theory and water shock propagation and attenuation characteristic, this paper combined the numerical simulation and studied the propagation and attenuation characteristic of shock in water produced by the explosion in rock of underwater borehole blasting under single free surface and dual free surface condition, and reached the study results as follow.1) Through simulating the shock in water produced by a single borehole on single free surface and damping in water condition, the water shock peak pressure was the superposition of dynamic water pressure and bubble pulsation peak pressure, and the effect of dynamic water motion and bubble pulsation was vertical direction. The water direct wave produced by the partial explosives in borehole orifice become the principle wave of shock in water away from the explosion source, and the direct wave propagated around in center of borehole orifice. The attenuation rule of shock in water after 11m away from borehole axes was confirmed to the attenuation rule regressed from the site test data. On the other factor no changed, the attenuation rule of shock in water of different water depth was compared. Following the water depth increasing, the water shock peak pressure attenuated more quickly in vertical direction. In the horizontal direction, the peak pressure attenuation become more quickly near explosion resource but become slow after 11m away from borehole axes.2) In underwater bench blasting with dual free surface, the mechanism of shock in water was different from single free surface condition. Through study the water shock propagation characteristic in minimum burden direction, parallel to bench edge direction and vertical to water bottom direction of underwater bench blasting, the results shows that the water shock of underwater bench blasting was produced by the whole explosive amount in borehole, and the water shock attenuated most quick in vertical direction, the parallel to bench edge direction's was next quick and the minimum burden direction's was the slowest. Under other factors no changed condition, the 5m, 10m, 15m water depth were, in the main, no influence on the propagation characteristic and attenuation rule of shock in water.3) The cofferdam was demolished by blasting with inner full water, water shock produced by horizontal borehole explosion in inner side concrete of cofferdam had directivity, and the maximum pressure of water shock existed in borehole axis direction, and the water shock pressure become small following away the borehole axis. The peak pressure attenuation of shock in water in borehole axis direction was slower than the direction vertical to the borehole axis. The monitor data and waveform of shock in water of a hydraulic engineering RCC cofferdam blasting demolition verified the directivity of water shock produced by cofferdam horizontal borehole, the maximum water shock pressure in borehole axis and the water shock pressure declined by away the borehole axis.