The mechanism of piping failure and disaster prevention systems

为探讨山体下气压对滑坡的影响，在九州岛进行了野外观测和大型洒水试验。在由九州白苏组成的台地，井中的气压几乎总是与大气压力相似，空气不会从井中流出。大气压下降时，气压大于大气压。在同一事件中，从另一个称为s3的井观察到气流。这些现象之间有一个时间差。s1在水系统中可能不同于s3，所以在“空气系统”中也可能不同。在实验中，我们把空气抽到沙坡下面。即使我们抽高压空气或低压空气，斜坡上的空气压力也没有太大的不同。然而，当我们泵入高压空气时，流量、压头、水力梯度等参数发生了明显的变化。因此，孔隙空气压力对滑坡的影响并不直接影响砂体，而是通过增加地下水水力梯度间接影响砂体。

To examine the effects of air pressure under the grand for the landslide, field observation in Kyushu island and a large-size sprinkling experiment were conducted. At tableland, which is composed of Shirasu, in Kyushu, nearly always air pressure in a well was similar to atmospheric pressure and air did not get out from the well. However air pressure was bigger than atmospheric pressure while atmospheric pressure was falling. At the same event, an air flow was observed from another well called s 3. There was a time lag between these phenomena. The s 1 may different from s 3 in water systems, so it might different too in "air system". In the experiment, we pumped air to under a sand slope. Air pressures in the slope were not different so much even though we pumped high pressured air or low pressured air. However, when we pumped high pressured air, water daters changed clearly, for instance, discharge, pressure head, and hydraulic gradient. Therefore, effect of the pore air pressure for the landslide do not affect sand directly but indirectly though increasing of the hydraulic gradient of groundwater.