| Bedrock cores obtained from Gamburtsev subglacial mountain provide critical scientificsignificance and social value not only on Antarctic earth science, microbiology and rock structurebut also on the relative research field of formation, movement and development of polar glaciersor even global climate. This thesis presents thorough introduction on current cable-suspendedelectro-mechanical drill for polar ice and subglacial bedrock exploration and classifications ofvarious types of antitorque system used by different countries. Particularly theoretical andexperimental research on two key technologies for design of armed cable-suspendedelectro-mechanical subglacial coring drill–large anti-torque device and low drill load (WOB)were discussed, which is on the behalf of preferred type selection for subgalcial bedrock drillingand research on mutual influence law between large antitorque system and low drill load. Themain achievements in this thesis are as following:1. According to theoretical calculations, the requested torque of armed cable-suspendedelectro-mechanical subglacial coring drill for ice and rock was determined and based on whichantitorque system was designed. On the basis of summarizing the types of antitorque system, thepaper proposes the antitorque system design principles and builds up the mathematical model forcalculation of its main parameters. Through theoretical calculation for leaf spring and skateantitorque system, the dependence of radial force vs torque was investigated, and the torqueworking rang of leaf spring and skate antitorque system were obtained. Leaf spring type, slideknife type and U shaped leaf spring were optimally designed and manufactured on the basis oftheoretical calculations. This paper presents a complete theoretical analysis on design parameterschoosing, mathematic calculation, mechanical designing for design of antitorque system of armedcable-suspended electro-mechanical coring drill, and lays an important theoretical basis for designof antitorque system.2. Antitorque system test stand was built to make performance tests on three differentantitorque system in ice holes with different temperatures. The experimental results show that boththe maximum anti-torque and sliding resistance of the same antitorque system decreased withdecreasing temperature of ice hole. At the same temperature of ice holes, skate antitorque systemcan provide maximum antitorque (67~267N·m), compared with U-shaped blade (6.5~138N·m)and leaf spring type (2.5~40N·m). Sliding resistance of skate antitorque system is within209~454N in vibration condition, and could achieve to1000N in static condition; slidingresistance of leaf spring type antitorque system is19.3~243N; sliding resistance of U-shaped bladeis12.1~551.9N, and when its thickness of blade is0.1and0.2mm sliding resistance is similar withthat of leaf spring antitorque system, while when the its thickness is0.5and0.8mm, slidingresistance is similar with that of skate antitorque system. Comprehensive considering the workingconditions of armed cable drill, skate antitorque system can provide both large anti-torque andsliding resistance, which can be used in bedrock drilling that needs high dead weight and largeantitorque; Leaf spring type antitorque system provide smaller antitorque and sliding resistance,and it capable to use in ice drilling that requests low dead weight and drilling torque; U-shaped blade antitorque system can produce larger sliding resistance than that of leaf spring type whenresists the same torque as leaf spring type, while it produce much smaller antitorque than skatetype with same sliding resistance as skate type. Thus U-shaped blade antitorque system does notsuit for armed cable-suspended electro-mechanical coring drill.3. Drill bit test stand was built to make performance tests on eleven different kinds of drillbits. The experimental results show: In the experimental WOB range, the specific pressure ofnormal bit is too low to drill granite with VIII drillability. Teeth drill bit owns small bottom liparea, high specific pressure and rate of penetration (ROP). The average ROP can achieve2.24m/hwith3kN drill load, which is rather higher than other types drill head. ROP of bionic diamond bitis a little bit lower than that of teeth bit but rather higher than that of normal diamond bit. Teeth bitcan obtain high ROP and simultaneously large torque (28.77~51.57N·m). Torque of bionic bit(E1~E3) is a little bit lower than that of teeth bit. Life time of teeth bit is shorter than that of otherbits. Predicted life time of teeth bit is less than4m, while for bionic bit is more than10m.4. It was concluded the skate type antitorque system is the best by contrasting the torqueparameters obtained from the drill bit experiments and anti-torque provided by different kinds ofantitorque system; Also interaction effect of results from both low WOB bit test and antitorquesystem experiment was analyzed. Effective WOB, ROP and accordingly drilling torque providedby drill at given gravity of drill decreases with increasing outer diameter of the skate styleantitorque system, which phenomenon declines with increasing weight of drill. Effective WOBand ROP provided by antitorque system of drill decreases at-10℃compared with-5℃. Withgiven drill weight3.5kN and5kN, the effective WOB at-10℃reduced3.3%and2.2%comparedwith that at-5℃. ROP at-10℃reduced about0.1m/h compared with that at-5℃. ROP oftoothed type diamond-impregnated bit at the same dead weight decreases with increasing outerdiameter of skate decreased which is less affected compared with that of bionic diamond bit,which at3.5kN of drill weight decreased3.7%while bionic diamond-impregnated bit E1and E2decrease9.9%and12.9%, respectively. Skate antitorque system affects least on ROP and canresist torque more than requirement during drill.Designed skate antitorque system and toothed drill bit with drill weight3.5kN can achieveROP more than3m/h, provide antitorque more than drilling demand and guarantee safety factor3.61, which satisfy drilling requirements of armed cable subglacial bedrock coring drill. |
PDF Full Text Request