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

根据研究计划，首席调查员首先推导出导致滑坡底部失稳的滑动速度。结果发现，失稳的滑动速度阈值在10米/秒量级，这是滑坡容易达到的（Kobayashi, 1997）。另一方面，合作研究者调查了岩浆川、凯达和圣海伦斯山等几个地点的碎片雪崩沉积物，并在碎片雪崩沉积物的底部发现了边界层的证据。他还发现，泥石流的流动机制，至少在最后阶段，可以看作是堵塞流动（Takarada, 1999）。负责人与合作研究者的合作研究遇到了困难，因为合作研究者在项目期间离开了日本进行研究。然而，他们经常通过电子邮件交流信息和观点，研究得到了很大的推动（一部分邮件包含在主要报告中）。随着该项目的原始研究，首席调查员对大型岩石雪崩的运动机制进行了回顾，并检查了他自己的假设的有效性（Kobayashi, 1999）。可以认为，岩崩机制可分为发育阶段、流动阶段和沉积阶段；也就是说，没有任何独特的机制能够贯穿整个阶段。在这方面，我们的假设，基底导波理论，也不能例外，它应该只在加速阶段使用，直到滑动速度超过不稳定阈值。

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.