Study On Technology Of The Cofferdam Demolition Blasting In Deep Water Conditions

Through a combination of research methods, such as theoretical analysis, model test, numerical simulation, study the theory of demolition blasting technology in deep water conditions systematically, analyze the influence that the water depth to the blasting effect, deduce the relationship between underwater demolition design weight and the land demolition design weight; solve the key technical problem of the cofferdam demolition blasting in deep water conditions, present the blasting block forecast model suit underwater environment, Established the relationship between specific charge and blasting block, through model test and numerical simulation, Further confirmed the water depth to blasting broken effect influence,falls reliability,law of movement and effect and so on was further confirmed; deduced the Immediate streaming over the maximum allowable size of blast fragmentation formula; According to the actual need of Three Gorges third stage RCC cofferdam blasting demolition. Studied on the related technology about cofferdam fall blasting demolition. The main work in this research includes:1. In fundamental research aspect of cofferdam blasting demolition, Based on land blasting effect mechanism, underwater blasting physical phenomenon, discuss the submarine drill hole blasting action mechanism, according to the analysis we can get that: Cofferdam demolition blasting has the action mechanism comprehensive characteristic with land blasting and underwater blasting, but more difficult than sole land blasting and underwater blasting. Through the cofferdam demolition blasting effect influence research from water depth we can get that the influence function from water can be ignored. The influence from water to radius of rupture presents that the water depth more bigger, the radius of rupture zone more smaller, The influence of broken effect and thrown distance from water is big, deduced that if we want to get the same blasting broken effect between underwater blasting and land blasting. The relationship between underwater blasting design charge and land blasting design charge, laid the theoretical foundation of underwater blasting charge. On the basis of analyze cofferdam demolition blasting may have harmful effects, According to the characteristic of cofferdam demolition blasting, we should pay more attention to some blasting harmful effect such as: blasting vibration,shock wave in water,swell and flyrock.Provide the basis for cofferdam demolition blasting safety protection.2. In the key technology research aspect of cofferdam demolition blasting in deep water condition, obtain that when the water depth is increase, the detonation velocity will drop, because the hydraulic pressure function make the density of emulsion explosive change, thus the detonation velocity was influenced, its drop rule is same with the rule that the influence rule of density of emulsion explosive to detonation velocity. Along with increase of emulsion explosive immersion time, the detonation velocity presents the declining trend, Because the hydraulic pressure function has accelerated the water seepage, makes the water content of emulsion explosive to increase, thus affects the detonation velocity. The result has important meaning to the explosive shaping of cofferdam demolition blasting in deep water as well as the explosive production in deep water condition and the explosive outer covering choice and so on, obtain that the influence of water depth,immersion time to high-precision plastic waterproof detonator and digital detonator is not big through the influence test research of water depth,immersion time to the detonators performance, provide the experimental material for use this kind of detonation equipment in deep water condition cofferdam detonation and underwater blasting. Based on analyze the blasting block forecast model combination with the change rule of explosive performance in deep water condition. Present the block forecast model suitable for underwater blasting. Based on analyze the formula of underwater blasting specific charge at present, put forward the amendment formula of underwater blasting basic specific charge, establish the relationship between underwater blasting basic specific charge and blasting block, calculate the must be used specific charge according to different blasting block requirements. Cause the calculation of underwater blasting specific charge to be more scientific and to be more feasible. Study the near zone blasting,the grout curtain blasting destructive effect mechanism emphatically in the safety control standard research aspect of cofferdam demolition blasting. Discuss its blasting vibration safety control standard.3. In the aspect of cofferdam demolition blasting model test and numerical simulation research in deep water conditions, further confirm the theory research achievement of water depth to blasting shattered effect through the aspect of cofferdam demolition blasting model test and numerical simulation in deep water conditions. Using the physical model testing and numerical simulation calculation that use the criteria which is similar to gravity, Simulate and analyze the process of cofferdam block dumping and its effect after blasting; the effect of Three Gorges third stage RCC demolition blasting proved that the used physical model testing and numerical simulation technology is effective, has the scientific nature, the sophistication and the usability.4. In the aspect of immediate overflow cofferdam blasting technology research, derived the formula of the maximum permission blasting block size that can be swept by the flow under a certain speed of flow condition, and analyzed the relationship between inner diversion tunnel and blasting block when the traffic flow in different circumstances, provide the computation basis of blasting block which is allowed for immediate overflow after cofferdam blasting. After the blasting block that is allowed is determined, determine corresponding blasting parameters according to use the forecast model of underwater block distribution to calculate specific charge. Thus solve the two main technology questions of cofferdam demolition blasting technology that is immediate overflow: the first, satisfy the request of determine underwater blasting block under a certain speed of flow condition; the second, the calculation of underwater blasting specific charge when we want to get this blasting residue. The project practice that import and export of diversion tunnel cofferdam demolition blasting in Xiaowan proved that we can succeed realizes the immediate overflow after cofferdam blasting when use the immediate overflow cofferdam blasting technology which is we have studied.5. In the aspect of cofferdam directional fall demolition blasting technology research, take Three Gorges third stage RCC cofferdam demolition as a example, study on the main technical problems of directional fall cofferdam demolition, such as falling space,falling pivot,the barrel chamber arrangement,falling reliability,charge calculation,the detonation network, to create the technology of directional fall blasting demolition. Merges the cofferdam blasting demolition construction plan to the cofferdam construction. This cofferdam demolition innovation idea is successfully applied to the Three Gorges third stage RCC construction and cofferdam demolition blasting project. The most advanced digital detonation was first time used to Three Gorges third stage RCC demolition blasting in domestic. The explosive ignite time is precise control to achieve reduced interference in shock and reduce the harmful effects of blasting vibration, make sure the safety of surrounding buildings, the safety monitoring achievement indicated that it was a very successful blasting. Three Gorges third stage RCC cofferdam demolition which was implemented by fall blasting demolition technology, created many records such as the total quantity of cofferdam blasting demolition,demolition difficulty,a detonation partition number, the burst time and so on, promote the development of cofferdam demolition technology in our country.