•6and16mmimpregnated diamondcoredrillsforcuttingofglass •16conventional hard-alloy-tipped drillforhand-heldhammering drills(Hilti) •16mmhard-alloytoolformetalcutting(4-mmcore) •16-mmcustom-made hardalloycoredrill(Ter_trio) •aconceptoftwosurgicalknifebladesrotatingat16-mmradius(~14-mmcore) •sometoolsweretestedalsowiththeaidofsonicvibrations, butwithoutanysuccess Hole Drillbit Materi_l Speed RPM [diamond (:)16 Marble 30 2[lardallo_ Marble 30 3"ttihi" Marble 30 4diamond OI6 Marble 31) 5hardallo_ Marble 31) 6diamond O6 Marble 30 7diamond 06 Marble 611 8diamond 016 Marble 6(I _tdi,unond 06 Limestone 30 I0 diamond OI6 Limestone 31) lIknifeblades. Limestone 31) 12 sonichardallo_ Limestone 30 I_s,anichardalto_' Limestone 30 14 sonichardalloy Limestone 30 ]5Teratrio Limestone 30 1,,5 Te_tno Granite 51) 17 rert_trio Oral1)te 120 18 Ter_itno Granite 121) It_sonicknifeblades Gratlitc 30 2(Ik_'.it_blades Gramte 3(I, 12O 21 Ter3trio iGranite 120 22 tt_:ttrio Granite 121)Force IHole ]Speed Njdepth/mm ]mm/h 24[8S/0._2.:_ 25l12,1 26 25I17..II.O 25[17.g [2.6 24/II.t Io.5..2,l 24I13,2 /°-7.2. 24115,1 tI'_'_ 24/671°33'_ 24]10,6 I17..3,4 25 3.4 I0 12 4,3 i15 12 6,1 I15 12 2.3 ]15 27 9,g I18 high 0.9 I3 high]6.2 ]36 27 23 I2.2 12 t.5 102 I2 l I0.2 45 3.1 I2.0 45 2.9 .2.g|)uterine b 4 5 14 65 6 b 8 4.5 5 0,5 Different sonic vibration 0.5 10minutes 10minutes 13 2 3 1.5 14 Figure12.Somepreliminary drilling testresults, materials andtools. Forenhanced orspecial sampling actions, twopowerlinesareroutedthrough drillpipecouplings toallow useofpossible activedrillingtoolsintheendofdrillstring.Thesepossible toolsinclude, forexample, percussive toolsandultrasonic tools.Dr.T.C.NgandHolinser Grouphavealready developed adesign forasuitable activepercussive toolinUniversity ofHongKong.Alsospecial measuring instruments can bemounted intoolsformeasuring temperature, contact force,etc.Aconcept toutilizeultrasonic vibration toenhance cuttingactionwasalsodeveloped andtested.Anultrasonic transducer wasdeveloped tofit insidethedrillpipe.Theresults show,however, thatwithgivenvolume itwasnotpossible togain reasonable mechanical amplification forvibration andtherequired electrical inputpowerrequirement became toohigh.Anultrasonic transducer inthissizeturnedouttobeuseless. Preparation foranomalies Theworstcaseaccident tohappen forthedrillwouldbetheonethatwouldseizeentireroverpreventing itfromreturning backtothelanderorcarrying outanyothertasks.Thiscanhappen ifthedrillstringgets stuckintheborehole, orthedrillsystem failstoseparate drillpipesfromeachother. Tobeprepared forsuchanaccident, thedrillsystem iscapable ofleaving theentiredrillstringintothe borehole astheroverbacksawayfromtheborehole. Thisispossible sincetheDSShasalongvertical slotinthefrontsideofthestructure, rightinfrontoftheactivedrillpipe.Alsodesigns ofthepipecarousel, clamping system, pipeholders, andtoolcarousel aresuchthatthepipecanbeabandoned andtherover canbebacked away. .Incasethedrillstringshouldgetstuckintheground, thedrillfirstpullswithfullpowerinhopeto separate oneofthecouplings onthestring.Ifonecoupling opens,thestringretraction canproceed in thepreplanned manner. Ifnoneofthecouplings open,itmeansthattheuppermost pipeisstuckin theground. Thenthesecuring wedgeonthespindle isreleased andthespindle isseparated fromthe string,afterwhichtherovercanbackaway. 2.Ifacoupling between twopipesisstuck,thosecannotbestoredinthecarousel. Inthatcasebothof themmustbeabandoned byreleasing themfromthespindle andleavingthemintotheborehole. 196