Laboratory experiments and thermal calculations for the development of a next-generation glacier-ice exploration system: Development of an electro-thermal drilling device

元データ 国立極地研究所

概要

A next-generation drilling system, equipped with a thermal drilling device, is proposed for glacier ice. The system is designed to penetrate glacier ice via melting of the ice and continuously analyze melt-water in a contamination-free sonde. This new type of drilling system is expected to provide analysis data in less time and at less cost than existing systems. Because of the limited number of parameters that can be measured, the proposed system will not take the place of conventional drilling systems that are used to obtain ice cores; however, it will provide a useful method for quickly and simply investigating glacier ice. An electro-thermal drilling device is one of the most important elements needed to develop the proposed system. To estimate the thermal supply required to reach a target depth in a reasonable time, laboratory experiments were conducted using ice blocks and a small sonde equipped solely with heaters. Thermal calculations were then performed under a limited range of conditions. The experiments were undertaken to investigate the effects of the shape and material of the drill head and heater temperature on the rate of penetration into the ice. Additional thermal calculations were then performed based on the experimental results. According to the simple thermal calculations, if the thermal loss that occurs while heat is transferred from the heater to ice (in melting the ice) is assumed to be 50%, the total thermal supply required for heaters in the sonde and cable is as follows: (i) 4.8 kW (sonde) plus 0 W (cable) to penetrate to 300 m depth over 10 days into temperate glacier ice for which the temperature is 0 °C at all depths and to maintain a water layer along 300 m of cable; (ii) 10 kW (sonde) plus 19-32 kW (cable) to penetrate to 1000 m depth over 1 month into cold glacier ice for which the temperature is -25 °C at the surface and 0 °C at 1000 m depth and to maintain a water layer along 1000 m of cable; and (iii) 19 kW (sonde) plus 140-235 kW (cable) to penetrate to 3000 m depth over 2 months into an ice sheet for which the temperature is -55 °C at the surface and 0 °C at 3000 m depth and to maintain a water layer along 3000 m of cable. The thermal supply required for the cable is strongly affected by the thickness of the water layer, cable diameter, and the horizontal distance from the ice wall at which the ice temperature was maintained at its initial temperature. A large thermal supply is required to heat 3000 m of cable in an ice sheet (scenario (iii) above), but penetration into glacier ice (scenarios (i) and (ii) above) could be realistic with the use of a currently employed generator.

著者

藤井 理行 国立極地研究所
Motoyama Hideaki National Institute of Polar Research, Research Organization of Information and Systems
Fujii Yoshiyuki National Institute of Polar Research, Research Organization of Information and Systems
Suto Yuko Graduate School of Environmental Studies, Tohoku University
Saito Sosuke Graduate School of Environmental Studies, Tohoku University
Osada Ken-ichi Graduate School of Environmental Studies, Tohoku University
Takahashi Hiroshi Graduate School of Environmental Studies, Tohoku University
Tanaka Yoichi Geosystems Inc.
本山 秀明 極地研
本山 秀明 情報・システム研究機構 国立極地研究所
Motoyama Hideaki National Institute Of Polar Research
Osada Ken-ichi Graduate School Of Environmental Studies Tohoku University
Yamanouchi Takashi Geosystems Inc.
Yamanouchi Takashi National Institute For Polar Research
本山 秀明 National Institute of Polar Research
Fujii Yoshiyuki National Institute Of Polar Research
Yamanouchi Takashi National Institute Of Polar Research Organization Of Information And Systems
Suto Yuko Graduate School Of Environmental Studies Tohoku University
Saito Sosuke Graduate School Of Environmental Studies Tohoku University
Fujii Y National Inst. Polar Res. Tokyo
Yamanouchi T Graduate Univ. Advanced Studies Tokyo
Yamada T Geosystems Inc.
Motoyama Hideaki National Inst. Of Polar Res. 10-3 Midori-cho Tachikawa-shi Tokyo 190-8518 Jpn
Yamada Tomomi Geosystems Inc.
Takahashi Hiroshi Graduate School Of Environmental Studies Tohoku University

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