Verification of the basal guided wave theory in reduced friction of large rock avalanches and its development

根据研究计划，首席调查员首先得出了导致滑坡底部不稳定的滑动速度。结果发现，滑坡的失稳门槛约为10m/S，这是滑坡很容易达到的(小林，1997年)。另一方面，合作调查员在岩川、凯达和山上调查了几个地点的崩塌堆积物。St.Helens发现了碎片-雪崩沉积物底部存在边界层的证据。他还发现，至少在最后阶段，岩屑雪崩的流动机制可能被视为推塞流(Takarada，1999)。负责人和合作调查员的合作研究遇到了困难，因为合作调查员在项目期间离开日本进行研究。然而，他们通过电子邮件频繁地交换信息和意见，极大地促进了研究(主报告中包含了部分邮件)。首席调查员结合项目的原始研究，回顾了大型岩石雪崩的运动机制，并检验了他自己的假说的正确性(小林，1999)。可以得出结论：岩石雪崩的机制应分为发展阶段、流动阶段和沉积阶段，即没有任何独特的机制可以贯穿整个阶段。在这方面，我们的假设，基本导波理论也不能例外，它应该只用于加速阶段，直到滑移速度超过不稳定性阈值。

In accordance with the research plan the head investigator first derived the slide velocity that causes instability in the base of a landslide. As a result it was found that the slide velocity threshold for instability is on the order of 10 m/s that is easily attained by landslides(Kobayashi, 1997).The cooperative investigator, on the other hand, surveyed debris avalanche deposits at several sites including Iwasegawa, Kaida, and Mt. St. Helens and found evidence for a boundary layer in the bottom of the debris-avalanche deposits. He also found that the flow mechanism of the debris avalanches, at least in the final stage, may be seen as plug flow(Takarada, 1999).Cooperative study by the head and cooperative investigators encountered a difficulty, since the cooperative investigator left Japan for study during the term of the project. However, they exchanged information and views by E-mail frequently and the research was promoted greatly (a part of the mails included in the main report).Along with original study of the project the head investigator made a review of the movement mechanism of large rock avalanches, and examined the validity of his own hypothesis(Kobayashi, 1999).It may be concluded that mechanism of a rock avalanches should be divided into those in the developing , flowing and depositing stages ; i.e. no unique mechanism can work through the whole stages. In this respect our hypothesis, basal guided wave theory, also cannot be an exception and it should be used only in the accelerating stage till the slide velocity exceeds the instability threshold.