Effect of the development of notches and tension cracks on instability of limestone coastal cliffs in the Ryukyus, Japan
Effect of the development of notches and tension cracks on instability of limestone coastal cliffs in the Ryukyus, Japan
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DOI：
10.1016/j.geomorph.2006.02.012
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发表时间：
2006-10
期刊：
影响因子：
3.9
通讯作者：
T. Kogure;H. Aoki;A. Maekado;T. Hirose;Y. Matsukura
中科院分区：
文献类型：
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作者：
T. Kogure;H. Aoki;A. Maekado;T. Hirose;Y. Matsukura
在日本冲绳的垂直海岸石灰岩悬崖底部，波浪切割出的缺口正在形成。崖高3.0 ~ 22.1 m，最大缺口深度8.8 m。在悬崖前的平台上发现了许多矩形或立方体的石块，这些石块似乎起源于悬崖的坍塌。在悬崖的平顶面上，张力裂缝往往与悬崖面平行。悬崖的垂直表面显示出小的起伏，但没有滑动条纹，这表明悬崖的破坏是由倾倒而不是由剪切或滑动引起的。我们利用边坡稳定性分析来确定倾覆破坏的临界条件。悬崖材料的物理和机械性能首先通过实验室试验获得。结果表明：石灰石的强度表现出尺度效应，随着试件尺寸的增大，其强度减小；根据这一结果，我们估计了与海岸悬崖大小相对应的岩体强度。然后用悬臂梁模型分析了悬崖的稳定性。通过稳定性分析与落块体尺寸的比较表明，倾倒破坏与缺口和张拉裂纹的发展密切相关。
Notches cut by waves are currently developing at the base of vertical coastal limestone cliffs in Okinawa, Japan. The cliff height varies from 3.0–22.1 m, and the maximum notch depth is 8.8 m. Many rectangular or cubic blocks, which appear to have originated from cliff failures, are found on platforms in front of the cliffs. On the flat top surface of the cliff, tension cracks often run parallel to the cliff face. The vertical face of the cliffs displays small undulations but no sliding striation, suggesting that cliff failures have been caused by toppling rather than by shearing or sliding. We use slope stability analysis to determine the critical condition for toppling failure. Physical and mechanical properties of the cliff material were first obtained from laboratory tests. The results indicate that the strength of limestone shows a scale effect, such that the strength decreases with increasing size of the test specimens. Based on this result, we estimated the strength of a rock mass corresponding to the size of the coastal cliff. Cliff stability was then analyzed using a cantilever beam model. Comparison of the stability analysis and the dimension of fallen blocks indicates that toppling failure is strongly associated with the development of notches and tension cracks.