| In21st century, the need for various resources is growing everyday with thecontinuous and fast development of social economy, and the recoverable reserves ofmineral resources are running out due to their non-renewable availability. In order toguarantee the sustainable development of economy and the society, the explorationinvestment as well as boundary must be enlarged, and efforts must be made to explorethe mineral resources reserved in deep formation or difficult working areas whiledrilling for the target of deep and unknown mineral exploring, such as the geologicalexploration in complicated formation, northeast arctic-alpine areas, remote westernregions and arid regions. Meanwhile, the drilling efficiency or ROP (Rate of Penetration)is low, the coring quality is not meeting the requirements of core drilling, theconstruction cost is high, the construction period is long, and even no way toaccomplish the drilling project targets due to the complicated formation and climate. Ina word, the above-mentioned problem of drilling technology is severe, and affecting thesmooth implementation of drilling project.As an advanced technology, the hollow-through DTH continuous coring andreverse circulation drilling technique is gradually focused on its application in order toresolve the above-mentioned problems. Furthermore, this technology combines highdrilling efficiency of DTH air hammer, reverse circulation in full hole with multiphase(Gas, Liquid and Solid) fluid medium, continuous rock debris discharge withoutdeclutching the drill rig, and continuous core drilling, and this drilling technology hasmany drilling advantages such as high drilling efficiency, high quality of borehole, highadaptive ability in complicated formation and the low construction cost. Therefore, this advanced drilling technology is deserved to extensive application in order to settleseries of drilling issues.Nowadays, the reverse circulation drilling technology with DTH air hammer hasbeen widely applied to drill in solid mineral resource exploration of slim hole, waterwell drilling and building foundation construction with rock-socketed piles etc.Therefore, this paper will emphasize on the mechanism study on reverse circulationdrilling with DTH air hammer, enriching the specification options for hollow throughDTH air hammer, optimizing the working parameters of DTH air hammer, achieving theconfiguration of equipment and reverse circulation drilling tools with DTH air hammer,seeking and completing the working parameters and drilling operation procedure,conducting the deep research on multi-process drilling integration of reverse circulationdrilling with DTH air hammer, enlarging the application region and working effect ofreverse circulation drilling, forming a systematic and complete drilling technique,contributing to the development of geological and geotechnical engineering.The research contents of this dissertation are as follows:1. The reverse circulation drilling technology with Down-the-Hole (DTH)hollow-through air hammer was systematically introduced and researched on drillingtools, the structure of drilling tools and working parameters of this reverse circulationdrilling technology. In addition, the dual-channel gas and water faucet, dual-walldrilling string, pneumatic DTH air hammer and reverse circulation drill bit as shownfrom above to below the drilling system are the specific drilling equipment of reversecirculation drilling technology with hollow-through DTH air hammer.2. The working mechanism of reverse circulation drill bit was intensivelyresearched with the skillful application of computational fluid dynamics softwareFLUNET, and the parameter variation and flow field of the drill bit as well as thebottom of the borehole are analyzed. Moreover, the structure of reverse circulation drillbit was innovated to assure the superior strength of the drill bit and dynamic parameterof the fluid within the bit. Meanwhile, the structure of the reverse circulation drill bitwas creatively designed to adapt to severely complicated formation, which could guarantee the steady formation of reverse circulation of multiphase fluid in the bottomof the borehole.3. The working performance parameter of the hollow through DTH air hammerwas researched by the means of computer simulation to let the hammer match with thehigh-pressure air compressor. In addition, the variation law of working parameter of theDTH hammer in different air pressure conditions was researched in the assumption thatthe mass of the piston of GQ-89hollow through DTH air hammer was4.9Kg. When themass of the piston changed, the impact velocity of the piston reached to the ultimatevalue8m/s. What’s more, some important conclusions are obtained after finishing theresearch on working parameters of DTH air hammer.4. The stress and strength of reverse circulation drilling tool with DTH air hammerwere studied with the application of finite element method (FEM) engineering softwareANSYS/LS-DYNA to enhance the strength and the service life of drilling tools.5. The drilling and exploring technique of reverse circulation core drilling withDTH air hammer, the operation method and the drilling specification parameters wereenriched and completed. Furthermore, the drilling and exploring technique of reversecirculation core drilling with DTH air hammer was detailedly researched to promote theprogress and development of this technology for the sake of nationwide popularizationand application.6. The method for collecting, clarifying, arrangement, packaging and transmittingthe obtained core was researched and innovated, and the problem of core acquisitionand collection in various hydro-geological conditions was settled, such as dry formation,moist and aquifer stratum drilling.Important conclusions are as follows:The influence of air pressure on DTH air hammer was researched, and the workingperformance parameter of DTH air hammer with various air pressure was optimized onthe basis of computer simulation，meanwhile the effective thermal efficiency and airpressure were also calculated. 1. The einmal impact energy of the DTH air hammer just depended on the mass ofpiston while sufficient compressed air was provided, and linear relationship waspresented with each other.2. The impact frequency of DTH air hammer was just related to the designed gasdistribution stroke of the hammer, nevertheless had nothing to do with the air pressureand mass of the piston.3. The rated air pressure of DTH air hammer was related to the mass of piston, andthe einmal impact energy and the rated air pressure of DTH air hammer increase withthe mass augment of piston. Furthermore, the drilling efficiency or rate of penetration(ROP) was increased with a large extent.4. The effective thermal efficiency of DTH air hammer decreased via the rated airpressure increased, and the high-pressure DTH air hammer must be assorted with highpressure air compressor. In addition, the drilling efficiency could be dramaticallyenlarged by using super-high pressure air compressor and developing new DTH airhammer with super-high air pressure. Meanwhile, the depth of drilled borehole could beenhanced and optimized, which would present a superior prospect for the application ofDTH air hammer. |
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