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.

在日本高山环境中，通过（1）破裂岩石样品冻结膨胀的实验室实验，（2）由于冻结引起的岩石接缝开口的现场测量，和（3）从冰斗后壁的落石活动的观测，研究了岩石壁的冻裂和由此产生的落石活动。在融雪季节，每隔1-10天调查一次所有落在雪上的石块的分布、轨迹和尺寸。连接到数据记录仪的电子传感器允许连续两年记录岩石节理的分离和岩石温度。在实验室中对断裂花岗岩块体的冻结膨胀和岩石温度进行了监测，现场测量发现了两次岩石节理张开事件，一次发生在隆冬，另一次发生在融化季节的早期。两者都表明，当充水接头在暂时融化后重新冻结时，会发生开口，这使得水渗透到接头中。室内研究表明，冻结膨胀在岩石温度降至-2 ° C以下之前就已完成，岩石节理在略低于0 ° C时就趋于张开。落石的数量和大小往往增加解冻渗透到岩壁。平均而言，最大的落石活动达到约10天后，从雪中暴露的岩壁。热传导理论表明，当融冰前缘深入岩壁1-2 m时，落石活动最大。

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)。

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。

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 and Hiroaki Sakai: "Rockfall activities from a cirque wall during snow-melting seasons" Transactions, Japanese Geomorphological Union. 17. 39-40 (1995)

Norikazu Matsuoka 和 Hiroaki Sakai：“融雪季节期间冰斗墙的落石活动”，日本地貌联盟汇刊。

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。