我国于2012年1月在南极Dome A区域正式开展实施了南极昆仑站深冰芯科学钻探工程,截至2021年,钻孔深度已达803.54 m.该工程是我国第一个深冰芯钻探工程,也是国际上第一个在Dome A地区开展的深冰芯钻探项目.本文介绍了昆仑站深冰芯科学钻探工程实施的整体情况,对过去近10年的钻探活动以及取得的成果和经验进行了总结,以期为后续的深冰芯钻探工作提供理论和经验指导.

Abstract A deep ice core was drilled at Dome A, Antarctic Plateau, East Antarctica, which started with the installation of a casing in January 2012 and reached 800.8 m in January 2017. To date, a total of 337 successful ice-core drilling runs have been conducted, including 118 runs to drill the pilot hole. The total drilling time was 52 days, of which eight days were required for drilling down and reaming the pilot hole, and 44 days for deep ice coring. The average penetration depths of individual runs were 1 and 3.1 m for the pilot hole drilling and deep ice coring, respectively. The quality of the ice cores was imperfect in the brittle zone (650−800 m). Some of the troubles encountered are discussed for reference, such as armoured cable knotting, screws falling into the hole bottom, and damaged parts, among others.

Abrasive belt grinding is the key technology in high-end precision manufacturing field, but the working condition of abrasive particles on the surface of the belt will directly affect the quality and efficiency during processing. Aiming at the problem of the inability to monitor the wearing status of abrasive belt in real-time during the grinding process, and the challenge of time-consuming control while shutdown for detection, this paper proposes a method for predicating the wear of abrasive belt while the grinding process based on back-propagation (BP) neural network. First, experiments are carried out based on ultra-depth-of-field detection technology, and different parameter combinations are used to measure the degree of abrasive belt wear. Then the effects of different grinding speeds, different contact pressures, and different work piece materials on the abrasive belt wear rate are obtained. It can be concluded that the abrasive belt wear rate gradually increases as the grinding speed of the abrasive belt increases. With the increase of steel grade, the hardness of the steel structure increases, which intensifies the abrasive belt wear. As the contact pressure increases, the pressure on a single abrasive particle increases, which ultimately leads to increased wear. With the increase of contact pressure, the increase of the wear rate of materials with higher hardness is greater. By utilizing the artificial intelligence BP neural network method, 18 sets of experiment data are used for training BP neural network while 9 sets of data are used for verification, and the nonlinear mapping relationship between various process parameter combinations such as grinding speed, contact pressure, workpiece material, and wear rate is established to predict the wear degree of abrasive belt. Finally, the results of verification by examples show that the method proposed in this paper can fulfill the purpose of quickly and accurately predicting the degree of abrasive belt wear, which can be used for guiding the manufacturing processing, and greatly improving the processing efficiency.

Shallow hot-water systems are well-known ice-drilling devices used to create holes for temperature measurements and monitoring of glacier dynamics, basal sliding, and englacial water-pressure. A shallow hot-water ice drill system designed at Jilin University is based on a commercial high-pressure washer, Karcher HDS 6/14C, that can deliver water at a temperature in the range of 80-155 degrees C, a flow of 4-10 L/min and a pressure as high as 14 MPa. The system also includes a mast with a sheave on the top and a reel with a 100-m long rubber hose; a 2m long, 60-mm diameter drill stem; a control and measuring system; sleds; a submersible pump; a return hose; a water tank with an affiliate heating unit; and a small 2-kW generator. Theoretical estimations were performed to predict the rate of penetration and mean diameter of the melted borehole. Experiments with a shallow hot-water drill were carried out in an ice drill testing facility to determine the relationship between the rate of penetration/borehole diameter and the diameter and type of nozzle, hot water temperature, and flowrate. Under a hot water flowrate of 10 L/min with a temperature of 60 degrees C, the 1.8-mm and 2-mm nozzles created 98-114-mm diameter boreholes at a penetration rate of 34-37 m/h, while a 2.5-mm nozzle produced a 146-156-mm borehole at rate of 26 m/h. The deviation between the experimental data and theoretical estimations did not exceed 7%.

Electric thermal drills are more advantageous than electromechanical drills in temperate, near-temperate, and polythermal glaciers because they can avoid problems arising from refreezing of we chips, which causes drills to become stuck in the borehole. When the refreezing rate of meltwater in borehole is expected to be too high and there is no considerable englacial water flow, thermal drills with meltwater removal system are optional for open-hole shallow (200-300 m) ice coring. To reach a sufficiently high rate of penetration of approximately 6-7 m h (-1), the power density of thermal head should be maintained in the range of 100-110 W cm(-2), which can be provided by tubular elements cast integrally with an aluminum or copper annulus. To remove meltwater via air reverse circulation, thermal drills can be equipped with a small blower. The safest and most even mode of water removal is lifting in the form of water film on the wall of air sucking tubes. The maximum water removal rate using a single water-lifting pipe via air reverse circulation created by a blower with a sucking power of 110 airwatts was similar to 0.35 L min(-1). Assuming a penetration rate of 6-7 m h (-1) and the outer and inner diameters of 135 and 110 mm, respectively, of the drill head, the meltwater should be removed at a rate not less than 0.8-1.0 L min(-1). In this case, at least three water-lifting pipes should be used in the drill.

The size distribution and shape characteristics of ice cuttings have a large influence on the efficiency of the transportation of cuttings by electromechanical auger drills and eventually determine the maximum possible rate of penetration. The size of ice cuttings is usually controlled and estimated by visual examination, but this is insufficient for the precise control and prediction of performance of ice cutting removal. To determine the patterns of ice cuttings, sixteen ice cuttings were sampled in the course of drilling in natural lake ice by an electromechanical auger drill at a temperature below −5°C. The cutter is 19mm in width, with a rake angle of 45° and a relief angle of 15°. Sensors are employed to measure the drilling-depth, drilling-time and rotation speed of the coring auger. This paper presents the size distribution and shape characteristics of cuttings under various drill head rotation speeds and rates of penetration by using a sieving and computer image-based method. The size distribution of the cuttings has an asymmetrical shape similar to a chi-square distribution. Approximately half of the ice cuttings by weight are classified as small sized (<0.6mm). In all of the sieving samples, the ice cuttings have prolate form with a ratio between the major and minor axis within the range of 1.35 to 1.97, averaging ~1.55.