| The application of the DTH reverse circulation drilling technology in rock and soil drilling engineering is gradually catching people's eyes. It is looked as a new technology after diamond drilling technology and is one of the technologies which have most application scope. The technology of chip continually removal by reverse circulation of DTH is one of directions of DTH drilling technology development. This technology centralizes three merits of drilling technology which include DTH fracturing rock, fluent removal by reverse circulation and continually obtaining sample in drilling. This technology uses double-well drilling poles. The air-condensed is put into drilling hole through the gap of double-well drilling pole ,the waste air expelled from DTH working is returned to ground carrying rock grain through the core of double-well drilling pole.The construction engineering college of JiLin University has always been researching on the technology of chip continually removal by reverse circulation of DTH. We have never stopped since"七.五"periods and now have made this technology at the world advanced level. Now the construction engineering College of JiLin University has successfully accomplished the CGS's projects"the research and development of high effective drilling technology under complex strata in the west in our country". Its working contents are the applying research of hollow DTH under complex strata condition. This paper is the continue research of the projects'working contents. The continue researches are as follows:1. Basing on the theory of percussive drilling, further study on the hollow DTH reverse circulation continuous coring drilling bit rock breaking mechanics.2. Using finite element analysis software ANSYS and 3-D modeling software Solidworks commence numerical simulation between rock and the bit of hollow DTH reverse circulation continuous coring drilling.3. Through the theory research and finite element analysis of action mechanics between rock and the bit of hollow DTH reverse circulation continuous coring drilling,analyses the factors which influence the length of core. As a result, we can optimize reverse circulation sample drilling bit's structure.4. Designing test device which could simulate the process of percussive-rotary drilling.Through theory study and numerical simulation, we systematically research the mechanics during ball-type teeth of hollow DTH reverse circulation continuous coring drilling bit drilling and coring. Obtain some conclusion as follow:1. we combine rock fracture mechanics ,rock damage mechanics and other solid mechanics theory, analyses rock dynamic characteristics, and obtain the conclusion:The process of percussive drilling can be considered as a process of rock which is continuous damaging and fracturing. In other words, under impact load the process of rock breaking could be regarded as: with energy dissipation, rock micromechanism damage accumulation, and then local rock appears macroscopic cracking, until rock whole destruction at last.2. By using infinite element software ANSYS to simulate the effect mechanism between bit-teeth and rock, we can explain why the top of core was cake frame, and the root of core was plane. The reason why the core length is regular, through elementary analysis, we think under constant absorbed-in-fracture energy and impacting frequency percussive drilling reach to some extent kinetic equilibrium3. Making use of the results of numerical simulation, we analyses the factors which influence the length of core, optimize reverse circulation sample drilling bit's structure. All of these will provide guide meaning for next step of starting percussive-rotary test research.4. We design test device which could simulate the process of percussive-rotary drilling specially owing to researching how absorbed-in-fracture energy, impacting frequency,load on bit, rotational speed, bit structure and bit-teeth type influence rock breaking efficiency and length of core; Finding out the mechanism and process of percussive-rotary drilling; validating the result of infinite analysis. And the test device can ensures test working go with a swing.We didn't find this kind of series studies domestically. This study is creative.Rock breaking is a complex process of energy transmission. In order to researching the essential mechanism of rock impact grinding, we have to build rock breaking model. These need us to put some theories of elasticity, wave mechanics, fracture mechanics and modern damage mechanics into rock breaking terrain, by the aid of numerical methods such as finite element method, finite difference method, discrete element method and boundary element method. Upon elasticity model, fracture mechanics model, damage mechanics model and other existing model to improve and perfect rock breaking model.The theoretical study on action mechanics between rock and bit under the condition of percussive-rotary here is elementary, more questions need to be discussed and researched more deeply. For simplified model during numerical simulation, we just calculate the impacting load and the effect between center bit-teeth. But the effect mechanism between bit and rock is very complex in real case. It is affected by alterative stress and fatigue. If the real work conditions are expected to be simulated, we must consider each bit-teeth at first, then build the 3-D model between bit and rock at the bottom of hole, and consider static pressure, impacting load, cornering force at the same time. In addition, the study on how drilling regulation parameters influence the length of coring is elementary too, we should combine with test to process more deep research. In a word, if we want to build precise mathematic model to realize the numerical calculation. More precise studies need to be made deeply, and more scientists need persevere to put their efforts.
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