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氷河の流れに基礎層の破片が及ぼす影響
Neal R Iverson1, Denis Cohen, Thomas S Hooyer
1Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011, USA. niverson@iastate.edu
Science (New York, N.Y.)
|July 5, 2003
まとめ
氷河内の破片は,移動に大きく抵抗し,かなりの切断牽引力を発揮します. 亜氷河層の破片層の高孔水圧は摩擦を軽減し,氷が破片の上に滑り込ませることができます.
科学分野:
- 氷河学 氷河学とは
- 地球科学 地球科学 地球科学
- 地質物理学 地質物理学とは地質物理学です.
背景:
- 氷河の移動は,亜氷河破片の存在と性質を含む基礎条件の影響を受けます.
- 氷河の運動と基礎摩擦に抵抗する残骸の役割は,歴史的に過小評価されてきました.
研究 の 目的:
- 岩盤のインターフェイスに,破片に富んだ氷が及ぼす切断牽引力を調査するために.
- 氷床下の破片層と氷の破片との相互作用の機械的振る舞いに対する孔水圧の影響を決定する.
主な方法:
- 厚くて滑りやすい氷河の下に実験を行った.
- 滑らかな岩床に2〜11%の破片を積んだ氷の切断牽引を測定した.
- 氷河下の破片層に施された孔水圧 (60〜100%の正常なストレス).
主要な成果:
- 破片に富んだ氷 (2-11%の破片) は60~200kPaのシーアトラクションを生み出し,これは総基礎シーアトラクションに匹敵する.
- 破片層の孔水圧の増加により,切断牽引力が著しく低下し,破片の変形が停止しました.
- 孔水圧が通常のストレスの60-100%に達したとき,氷は破片層の上に滑り,滑り抵抗が破片の切断抵抗よりも低いことを示しました.
結論:
- 氷河下の破片は,氷河の基礎抵抗において重要な役割を果たし,以前は,摩擦が軽微であると仮定されていたが,これは逆である.
- 孔水圧は,潜在的に基礎滑りにつながり,氷河のダイナミクスを影響する,氷河下の摩擦を調節する重要な要因です.
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