Mechanisms of bedrock frost shattering and associated rockfall generation

基岩冻裂及相关落石产生的机制

• 批准号: 06680157
• 负责人: MATSUOKA Norikazu
• 金额: $ 1.34万
• 依托单位: University of Tsukuba
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06680157/
• 关键词: Periglacial; Weathering; Mass movement; Freeze-thaw; Frost shattering; Rockfall; Field measurement; Mountain

Frost shattering of rockwalls and resulting rockfall activity were studied in a Japanese high mountain environment by means of (1) a laboratory experiment of freezing expansion of a fractured rock sample, (2) field measurements of rock joint opening due to freezing, and (3) observations of rockfall activity from a cirque backwall. Distribution, trail and dimensions of all rock blocks fallen on snow were investigated at 1-10 day intervals during snow-melting seasons. Electric sensors connected to data loggers permitted continuous recording of separation of rock joints and rock temperatures for two years. In the laboratory, monitoring was made of freezing expansion of a fractured granite block and rock temperatures.Field measurements revealed two events of rock joint opening, one in midwinter and the other in early melting season. Both indicated that opening occurred when a water-filled joint was refrozen following temporary melting which allowed water to percolate into the joint. The laboratory study showed that freezing expansion was completed before the rock temperature was fallen below -2ﾟC.These results suggest that rock joints tend to open at a little lower than 0ﾟC.Thawing of the seasonally frozen rockwall which underwent joint opening during the freezing phase can result in the release of rock debris falling onto snow-covered talus slopes. The number and sizes of the rockfall debris tended to increase with thaw penetration into the rockwalls. On average, the maximum rockfall activity was reached about 10 days behind the exposure of the rockwall from snow. The thermal conduction theory indicated that rockfall activity was maximized when the thawing front penetrated to 1-2 m depth of the rockwalls.

通过（1）在日本高山环境中研究了冰墙的霜冻和产生的岩石活动，该实验室通过（1）实验室实验冻结了骨折的岩石样品的扩展，（2）由于冷冻而导致的岩石关节开口的现场测量，以及（3）从Cireque Backwall中观察到岩石坠落活动的观察结果。在雪融化的季节，以1-10天的间隔调查了所有岩石块的分布，步道和尺寸。连接到数据记录仪的电动传感器允许连续记录两年的岩石接头和岩石温度的分离。在实验室中，监测是通过冻结的花岗岩块和岩石温度的冻结膨胀进行的。场测量显示了两个岩石关节开口事件，一个在仲冬，另一个在熔化的季节早期。两者都表明，当暂时熔化后富含水的接头重新融化时，就会发生开口，从而使水渗透到关节中。实验室研究表明，在岩石温度降至-2 ﾟC以下之前，冻结膨胀完成了。这些结果表明，岩石接头倾向于以低于0 ﾟ的频率开放。C。季节性冷冻的岩壁大吃一惊，在冰冻阶段进行关节开口可能会导致岩石碎片释放到落入雪地覆盖的谈话插槽上。岩石碎片的数量和尺寸往往会随着融化渗透到岩壁上而增加。平均而言，最大的落叶活动在雪中暴露于雪地后约10天。热传导理论表明，当融化的前部穿透到岩壁的1-2 m深度时，岩石活动的活性被最大化。

项目成果

松岡憲知: "岩盤の凍結破壊に関する野外観測" 地形. 17. 40 (199)

Kentomo Matsuoka：“基岩冻结和破裂的现场观察”地貌学 17. 40 (199)。

松岡憲知・酒井裕晃: "融雪期におけるカ-ル壁からの落石の発生過程" 地形. 17. 39-40 (199)

Kentomo Matsuoka 和 Hiroaki Sakai：“融雪季节卷壁落石的生成过程”地貌学 17. 39-40 (199)。

Norikazu Matsuoka: "A laboratory simulation on freezing expansion of a fractured rock" Annual Report, Institute of Geoscience, University of Tsukuba. 21. 5-8 (1995)

Norikazu Matsuoka：“裂隙岩石冻结膨胀的实验室模拟”年度报告，筑波大学地球科学研究所。

Norikazu Matsuoka: "Field measurements on frost shattering of fractured rockwalls" Transactions, Japanese Geomorphological Union. 17. 39 (1995)

Norikazu Matsuoka：“裂缝岩壁霜冻破碎的现场测量”交易，日本地貌联盟。

Norikazu Matsuoka: "A laboratory simulation on freezing expansion of a fractured rock" Annual Report,Institute of Geoscience,Unirersity of Tsukuba. 21. 5-8 (1995)

Norikazu Matsuoka：“裂隙岩石冻结膨胀的实验室模拟”年度报告，筑波大学地球科学研究所。