| The Air-DTH hammer drilling technique is one of the most promising and widely used in drilling and construction technologies in the present words. It is used compressed air as the dynamic medium and cleaning solvent, and it takes the percussive-rotary drilling technique to break rock. With the development of science and technology and need of engineering, the DTH drilling technique has been developing continually, many new drilling tools and drilling technique methods are invented one after the other. From the general DTH hammer to the hollow-through DTH hammer reverse circulation drilling technique, the multi-techniques drilling technique is developed at the basis of single drilling technique.The Hollow-through DTH hammer reverse circulation drilling technique is regarded as the advanced DTH hammer drilling technology, which integrates three advanced drilling methods of DTH hammer fracturing rock, fluent removal by reverse circulation and continually obtaining core and sample during drilling. In the new round of geological exploration, the western region resources exploration, crisis mines replacing investigation and reclamation of resources become the working focus. In the drought, water shortage and complex formation regions, the Hollow-through DTH hammer reverse circulation drilling technique with its own unique technique advantages, could be got a wide range of promotion and application. This kind of technique has been applied successfully in practice after several years' study and test. However, in the face of complex geology and construction conditions, there are also many problems needed to be solved. Therefore, the CGS's projects "shallow layer sampling drilling equipment development and drilling technological method research" was set up to support the research. The paper is based on this project, the theory and technique studies on the problems existed in hollow-through DTH hammer reverse circulation drilling technique were done, and at the same time, the drilling structure was designed. These had been solved some problems during process of the production application. When the Hollow-through DTH hammer drilling was in process, it could transport the large particles of the rock sample and the schistose core. The flow dynamic characteristics of gas medium when it was circulating in the double-channel drill pipe were including the required gas volume and gas pressure increased in the hole depth, the pressure distribution of the gas in the double-channel drill pipe, and so on. Aiming at these to develop research, it was theoretical support to formulate appropriate process parameters and to further study reverse circulation mechanism. In this paper, the fluid medium pressure distribution and the speed change during the DTH hammer reverse circulation drilling was got preliminary study. Further more, it was built up the mathematical calculation model, which was supported theoretical basis to research the DTH hammer reverse circulation drilling. Through the mathematical calculation model, it could obtain the minimum gas volume with different hole depths and the pressure distribution of the double-channel drilling tool reverse circulation system. The theoretical calculation results were slightly less than the actual results when the test drilling parameters used in comparison.The special reverse circulation bit was the key part of the reverse circulation drilling system. In order to perfect the structure of the bit, the theoretic and practical studied on the bit have been done. Based on the computational fluid dynamics (CFD) theory, used engineering fluid dynamics software-FLUENT, the bit flow field was simulated with CFD. According to the productive tests and theoretical calculations to determine the reasonable boundary conditions and the entry-exit conditions, the different specification bit used in the Geological core exploration were calculated. We got the regularities of distribution of pressure field, velocity field, thermal field and the gas mass flow. At the same time, the influence of the size and position of bottom nozzles on the bit bottom flow field was simulated, and the influence of the size and position of injector hole on distribution of pressure and velocity field was simulated, and the influence of the bit diffusion groove shape on the bit bottom flow field was simulated. The area proportional relation of injector hole and bottom jet orifice was analyzed. We can get following conclusions: 1. When the bottom nozzle is away from the drill axis, the effective cross flow area is gradually increasing, and the reverse circulation effects are good. 2. The problem of air leaking in broken formation can be solved by using reverse circulation bit with inner jet orifices. Low pressure zone is formed above the inner jet orifices for its pumping function, which can reform the shape of flow field at the hole bottom and strengthen the reverse circulation. The reverse circulation can form successfully even if the formation is complex and leaking seriously. 3.Smaller value of aangle, the inclination of inner jet orifices, is good for formation of reverse circulation. But 25°is a ciritical point. When the value of ais between 20°and 30°,the reverse circulation can form successfully. 4. When drilling in the complex and fragment strata, it should increase the flow cross section area of the injector hole. The results of analog simulation play an important part in optimum design of structure and size of reverse circulation bit and curtailing the spending of time and money in researching which was good for further test research of hollow-through DTH hammer. At the same time, it is designed the outer annulus-suction type reverse circulation drilling bit and device of strength aspiration for hole batton. in order to capture the rock powder which is accumulated in the annulus of the drill tools and hole bottom during the reverse circulation drilling.The Hollow-through DTH hammer was used the reverse circulation to access the core, which was favorable to protect the integrity of the hole wall and to raise the core recovery rate, and it is especially applicable the application of complex formation. The formation features of hebeizhoulu silver mining area were mainly volcanic tuff, hornfels, diorite and quaternary overburden, the fracture zone development, the existence of underground mined-out area, the rock hard and leakage, poor stability, the easy collapse of the accident-prone hole. Because of the scarcity of water resources within the mining area, the drilling efficiency was low when used the conventional drilling methods, and the rock recovery rate was also low. In contrast, when used the hollow-through DTH drilling technology, determining the reasonable drilling parameters, there were completed 7 drill holes 824m drilling workload, so they had provided detailed technical information for geological exploration of the mine area. In addition, compared to the small caliber diamond drilling and central sampling C·S·R drilling technique, the drilling to use the hollow-through DTH drilling technology could increase the drilling efficiency and core recovery rate.Luanchuan molybdenum-tungsten mine located in Henan province is the biggest molybdenum mine in china, the formation of the mine zone belongs to classical complex strata. In recent years, owning to the frequent collapses of underground mined-out areas, it made the already broken formation into more complex, when using the conventional drilling methods, the pore was not formed at all. Aiming at the existed technique problems, it was further studied on mainly using the hollow-through DTH hammer drilling technology, auxiliary with the pipe-follow drilling and C·S·R drilling technique, and developed the productive tests in the complex strata in which the hole could not formed with the conventional drilling method, to complete the 44 drill hole. And among them, there were 24 holes facing the underground mined-out areas. The greatest height of the underground mined-out area was 34m, and the accumulated productive test workload was 2080m. The above all which were provided a very important geological data for the mine production safety and production plans, had achieved remarkable economic and social benefits.In the course of the experiment, the GQ89 piston was prone to breakage and damage, so further study its force condition. Firstly, it was used the stress wave theory to analyze and calculate the compressive stress wave and the tensile stress wave formed by the piston impacting movement, in order to find the position of the greatest compressive stress and tensile stress. And then the finite element software-ANSYS was used to analyze its dynamical stress and strain, which were provided the basis for the structure optimized design. The intensity of the new design GQ89 Piston had been a substantial increase.According to theoretical calculations and field productive test, it was relatively developed the series hollow-through DTH hammer air reverse circulation drilling parameters and the accident treatment methods in order to guide the actual production, and to solve the problems and accidents during the production process.The main creative point in the paper article:1. Estabish the calculation model of fluid mechanics parameter. It can solve the supplied of air and condition of pressure distribution, through calculate the model, perfect the basic theory of DTH hammer reverse circulation drilling.2. Formation a suit of integration drilling technique which is suitable for geologic survey in complex formation, through research of field productive test and drilling tool optimization.3. Creative designed the drilling bit of outer annulus-suction typer and the device of strength-aspiration for hole bottom.4. Optimzated the framework of reverse circulation bit using the software Fluent based on the theory of CFD.The applications in practice show that the technique of coring continually by reverse circulation with hollow-through DTH hammer is of abroad using field and can be used widely in solid mineral and resources exploration. The DTH drilling technique has many advantages, such as higher rate of penetration, high percentage recovery of core and sample, lower cost of drilling, the ability to adapt to complicated strata and so on. Via the theoretical study, the productive tests, the reverse circulation bit design, and the exploration and improvement of the parameters, this drilling technique as an advanced drilling technique has been formed the perfect equipments, applicable to the complex strata drilling, and it is of the advanced level in international domain.
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