Research On Increasing Core Length For Consummating Hollow DTH Reverse Circulation Continuous Coring Drilling

With the social development,energy crisis and shortage of mineral resourcesappears.The mineral situation steps into the recovery period in the world.The marketsbecoming avtive.In recent years,Tasks of coring drilling are increasing quickly.Toinvestigate and appraise mineral,The work loads of coring drilling are growthingsuddently.Without adoubt,we may foresight they will maintain for a longperiod.Appearing and shallow mineral become more and more few.Drilling will bedifficult,coring dilling will be more difficult.With the depth increasing,we willconstruct in a more complex geological condition:more in hardly,crisp,garrulous,leaks,caving in and so on.Former drilling methods have many shortcomings,forexample:low efficiency,bad quality,short life of the bits,many accidents,highcost.Hollow DTH reverse circulation continuous coring drilling may solve thequestions all above very well.The coring efficiency can achieve above 98%,but the coring length is only about10mm.At present,the geological departments request they are about 50mm atleast,which has limited the using scope of this technology.Realizating this goal is keypoint of this paper.Now the construction engineering College of JiLin University has successfullyaccomplished the CGS's project"the research and development of high effectivedrilling technology under complex strata condition in the west of our country". Itsworking content is the applying research of hollow DTH coring drilling technology inprospecting for solid mine. This paper is the extended research of the project and weare applying for initiating a project.The contents of research are as follows:1.Under the static load,the impact load,the rotation load and three couplingfunctions,I have researched the mechanism of staving rock systematically.2.The existing models of stave rock by impact and rotation load are notreasonable,the new one has been discussed.3. The mechanism about the teeth of bits of hollow DTH reverse circulationcontinuous coring drilling stave rock has been analyzed.4. the factors which influence the coring length is analyzed,for example:impactpower, frequency,pressure, rotation speed,bit structure,tooth type,and so on.5. I designed a test device and 8 bits,a lot of experimentation has been made.Some conclusions are got:1. DTH impact turn broken rock can be seen as a dynamic load, static load, cutting and the cumulative effect of superposition, the rock drilling process can be broken asa continuous cycle of damage and fracture process. This means that the impact of theprocess of crushing load of rocks is the essence of rock in the internal energydissipation, resulting in the accumulation of rock micro-structural damage, localproduce macro-crack, until the whole process of breaking broken. Is the type of leap.2. The ball-teeth, wedge-shaped teeth and tooth-breaking mechanism of thecontrast drawn: 1) the rock-crushing process leap forward. 2) No matter how theshape of the tooth bit, in terms of static and dynamic load or load broken rock, rockcrushing process to form the main pressure on the nuclear area and powder. 3) thenature of rock broken angle changed little in between to change. 4) the ball than thetooth of the total power consumption than the wedge-shaped teeth low. Spherical forma broken tooth broken the pit need to be greater than that of wedge-shaped teeth,broken by an even greater volume, the impact of large, high-efficiency; wedge-shapedteeth broken small pit, a small sphere of influence. Conical teeth in between. In orderto reduce the length of the core columns on the impact of teeth, tooth inner ringshould be as much as possible the use of non-small spherical ball or button.3. To impact on DTH the turn into broken rock analysis of the model used in thepast, different weaknesses, remains the main areas in Newton's mechanics; wavedynamics research results despite a more truly reflect the impact of the rotary drillingsystem dynamics characteristics, However, the system model of the mechanicalelements of the model over-simplification, the need to be further refined andimproved, the author of the cutting bit + load the impact of broken rock under themechanism of the drill bit and rock interaction study, the more accurate method toestablish model Discussed.4. produce the core ofΦ89 reverse circulation drill coring test with skirts is toshow the impact of using test-bed to turn a real simulation of the impact turn intoactual situation.5. Core columns would have an impact on teeth, great size, the impact, the samesize range of different effects of different profile, spherical cone is greater than toothscope of the impact of the ball teeth.6. The pilot study targeted the impact energy, to the number of parameters suchas core, they found that the impact is far from the structure of the drill bit.High-impact, and the bit for the structure of the trial were as follows: Drill impact oftooth profile of the core is far from the perspective of welding set of teeth and toothsize specifications of the high-impact.7. With testing ofΦ89 reverse circulation drill core, inner cone ball set teeth protruding center of the drill, mixing diamond-studded film in the first column,double-cone drill column gear-type gear teeth of the ball coring drill have found thatthe core columns The edge because of damage resulting from the impact caused bythe radial cracks,Φ89 reverse circulation drill core as well as an inner circle of indentsettings set the ball oblique teeth caused by the role. 4 single-row roller bit basic typesof gear that no damage is produced by small and short radial cracks.8.Φ89 reverse circulation drill core, inner cone ball set teeth protruding center ofthe drill witch tested access to the core of about 10mm in length, it is because we arebeginning to have impact on lateral crack, crack side is the core cause of the breakThe main factor in the depth of the lateral cracks in the vicinity of 0.8a, two bits areinclined to adopt a set (if there will be very different straight set), a similar, thefracture occurred in almost the same 0.8a is 10mm About broken.9.Φ89 reverse circulation drill core, inner cone ball set teeth protrudingcenter of the drill core tests have skirts, which are due to side-effect of crack locationis not a core diameter, but a nuclear compaction land.10. Diamond-studded film mixed in the first column, the column-type rock bit ofgear teeth ball coring drill cores have not achieved because of columns skirt close tothe film is a core part of a three-pyramid apex, the category of small-size alloy conebit, both pressure Is the nuclear core are small and close to the outer edge of the formof short lateral cracks, the core of a broken bit different from the first two, is notcaused by lateral cracks.11. Column mixed diamond-studded film in the first test of the core chip isdue to a broken tooth shear large area, turning resistance, cut the damage caused by aneven greater when the rotary drill bit cut before the rock edge, the edge because ofpre-rock core attached Site, so in the role of torque, the core has been broken.12 Oblique set inside the tooth row core columns would have caused sideeffects squeeze is not conducive to the formation of core length.13. Conical bit column-type gear teeth of the ball coring bit in particular, only 4of the symmetrical arrangement of single tooth drill tests made for a cylindrical coreand core of very good quality, especially in the upper part of the core is verystructured, The writer believes that the core columns because of a broken toothloosening, in turn under the horizontal force, stirring, resulting in a broken columncore, broken. This bit more appropriate size, the need for a reasonable fabric of thetooth, in addition to the exclusion of other core of the tooth row almost no impact onthe provision of adequate space bit design, if there is no welding set off the problemcan be loose alloy access to the integrity of a good long core. 14. Based on plenty of experienced and theories,I have designed third 3 bits.2 kindsof themhave got 2 cores(81.6 mm and 55 mm)in 2 kinds of test-rocks.all of these showed that the bitswere right,Successfully achievd the target of my research in this paper。The theoretical study on action mechanics between rock and bit under thecondition of percussive-rotary here is elementary, more questions need to be discussedand researched more deeply. the study on how drilling regulation parameters influencethe length of coring is elementary too, we should combine with test to process moredeep research. In a word,if we want to build precise mathematic model to realize thenumerical calculation. More precise studies need to be made deeply,and morescientists need persevere to put their efforts.