| With the gradual implementation of the marine development strategy,underwater projects have gradually moved from inland rivers to near seas,shallow seas to deep seas.Deep-water blasting is an inevitable trend in the development of underwater blasting projects in the future.The complex and changeable marine environment(wind,waves,currents)and changes in water depth have put forward new requirements for underwater blasting construction equipment,construction techniques,and safety protection.The shock wave effect of underwater blasting is not only the basis of underwater rock fragmentation,but also the main source of the harmful effects of underwater blasting.How to use explosive shock waves to effectively break rocks,reduce bedrock damage,and weaken its harmful effects has always been a hot and difficult research field in the field of underwater blasting.Therefore,studying the basic characteristics of underwater blasting shock waves under deep water conditions,improving the ability of underwater rock breaking by shock waves,and seeking effective safety protection theory and methods for deep water blasting shock waves have important theoretical significance and engineering value.Based on the "Blasting Engineering of the Main Tower Foundation of the Jintang Island Side of the Xihoumen Road-Railway Bridge of Yongzhou Railway" as the background,the thesis carried out a series of theoretical,experimental and simulation analysis around the basic characteristics and protection of the shock wave of drilling and blasting in deep water.Especially in the protection of bedrock damage and deep water shock wave bubble curtain protection,the "Deep-water drilling and blasting bedrock damage protection method based on the composite energy dissipation structure in the hole" and the "high-pressure gas instantaneous release air curtain" are proposed.Deep-water shock wave protection method",carried out the research on the theory of energy dissipation in underwater drilling and blasting hole and the theory of random distributed air curtain choke wave,and conducted in-depth research and exploration of its protection mechanism,protection effect and evaluation method respectively.(1)The law of shock wave propagation and attenuation in underwater drilling and blasting in 40 m,65m,and 90 m deep water environments and the influence of different hydrostatic pressures on the propagation and attenuation of shock waves in the bottom water are analyzed.The study found that the shock wave peak attenuation in the horizontal and vertical directions decays exponentially with the increase in distance;under different water depth conditions,the shock wave attenuation speed increases with the increase in water depth,near the bottom and in the waters near the blast-hole.The initial shock wave peak value is larger,but the attenuation is the fastest as the propagation distance increases,but the shock wave peak value near the bottom within200 m is basically higher than the water above it;based on the EMD method combined with the Hilbert transform,deep water drilling The shock wave signal in the blasting water was analyzed,and its time-frequency characteristics and energy distribution law were revealed.(2)According to the theory of transmission and reflection effects of stress waves propagating in the medium,a theoretical study on "Deep-water Drilling and Blasting Bedrock Damage Prevention Method Based on Composite Energy Dissipation Structure in Holes" was carried out,and a 40 m water depth environment was carried out.Indoor simulation test,through analysis of sample appearance,crack distribution and shape and size of blast hole cavity,it is verified that the composite elimination structure composed of high impedance sphere and coarse sand cushion can effectively reduce the hole base in underwater drilling and blasting.Rock damage improves the protective effect of the upper part.A wave analysis method based on the active monitoring of PZT piezoelectric ceramics is proposed,and the concrete damage index based on the wave energy RMSD is established,and the concrete damage range and the damage depth of the hole bottom under the protection of the energy dissipating structure are quantitatively analyzed.Research has found that the blasting medium in underwater drilling and blasting will cause a sudden change of damage at the bottom of the blast hole.The sudden change of the blast hole with energy dissipation structure is greater,and the mutation point is closer to the bottom of the blast hole;combined with the damage depth test and calculation,The minimum damage point of the sample with energy dissipation structure appears at the bottom of the hole 20 mm,which is 25% less than the damage depth of the sample without energy dissipation structure.At present,the research results have been applied to the "Blasting Project of the Main Tower Foundation on the Jintang Island Side of the Xihoumen Road-Rail Bridge of Yongzhou Railway".(3)On the basis of the traditional bubble curtain protection technology,a "underwater shock wave protection method based on the instantaneous release of high-pressure gas air curtain" is proposed.Based on the consideration of the morphological characteristics of the air curtain,the formulas for the transmission and reflection coefficients of the air curtain to the shock wave in the water are refined.On this basis,a small indoor high-pressure air curtain generator was built,and the air curtain form high-speed photography and shock wave pressure test experiments were carried out.The study found that with the increase of the gas source pressure,the continuity of the air curtain is enhanced and the gas energy flow density is higher and the ability to resist external load interference is increased.The duration of the air curtain also increases;according to the shock wave test results,combined with signal analysis,It is found that the attenuation rate of the shock wave peak at 50 cm of the explosion source by different high-pressure air curtains is 32.3%?76.7%,and the total energy attenuation rate is32.7%?71.4%.The higher the air source pressure,the better the protection effect.(4)Considering the influence of morphology on the effect of air curtain wave,a method for constructing a calculation model of bubble curtain in water based on random distribution is proposed,which realizes the random placement of bubbles in the air curtain area.This method highlights the air curtain.The characteristics of regional gas-liquid coexistence,changeable boundary contour and highly discontinuous and non-uniform gas distribution have enriched and perfected the construction method of numerical calculation model of underwater blasting shock wave air curtain. |
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