Estimation of the occurrence of a volcanic mud flow based on the theory of liquefaction of a volcanic ash layer caused by vibration of an earth quake or impact force of a slope failure

在本研究中，首先试图弄清楚火山灰层在地震振动或边坡破坏的冲击力作用下的流化机理。位于火山堆积物之间的火山灰层是由活火山地区的火山灰落下而形成的，接下来，根据上述振动或冲击力的作用导致的火山灰块液化的理论，预测火山泥流的发生。结果表明，由火山灰和水组成的泥浆的流变性试验结果表明，当其体积浓度超过15%时，可以定义为完全的火山泥浆流。当低频振动作用于浓度大于48.5%且仅含火山灰的泥浆时，泥浆的抗剪效果明显，其抗剪阻力随振动次数的增加而增大。 ...更多信息 状态。当其浓度达到66%左右时，完全呈现塑性，其高贵性大大降低。但是，当小砾石混入泥浆中时，由于泥浆中的颗粒尺寸不像仅由火山灰组成的泥浆中的颗粒尺寸那样均匀，因此防止了水化作用，并且增加了其流动性。当混合比为40%左右时，其流动性最大。在浓度低于66%的情况下，用5周/秒的低频振动和1cm- 2cm的振幅，在几秒钟内，火山灰团就很容易流化，当火山灰层受到类似地震的高频振动时，其发生运动的临界角减小20 °-高浓度福尔斯浆体的表观内摩擦角比低浓度浆体的表观内摩擦角小得多。这意味着，即使在一场小雨中，在活火山地区，火山灰层也很容易因地震或边坡破坏的冲击力等振动而液化。少

In this study, first it was tried to make clear the mechanism of the fluidization of volcanic ash layer by the vibration of an earth quake or impact force of a slope failure. This volcanic ash layer lain between volcanic accumulations is made by falling ash in an area of active volcano, next it was to predict the occurrence of a volcanic mud flow based on the theory of liquefaction of the mass of volcanic ash caused by the action of vibration or impact force stated above. As a result, the followings could be clarified.Judging from the result of the rheological test of a slurry consisted of volcanic ash and water, it can be defined as an entirely volcanic mud flow when the volumetric concentration of it is over 15%. When the vibration with low frequency acts on a slurry with the concentration of over 48.5% which consists of the only volcanic ash, the effect of dilatancy presents conspicuously itself, and the shearing resistance force of it increases in accordance with the number of vibr … More ation. When the concentration of it gets to about 66%, it presents entirely plasticity and the nobility of it decreases greatly. But the effect of dilatancy is prevented and the mobility of it increases when small gravels are mixed into that slurry, because the particle sizes in the slurry are not so homogenious as those in the slurry consisted of the only volcanic ash. The mobility of it gets the highest at the mixing ratio of about 40%. The mass of volcanic ash is easily fluidized in only few seconds by the vibration with low frequency of 5 cycle/sec and the amplitude of lcm- 2cm in the concentration below 66%.When a volcanic ash layer suffers from the vibration with high frequency like an earth quake, the critical angle for the occurrence of the movement of it decreases by 20ﾟ - 30ﾟ in comparison with that in the usual state when any vibration dose not act on it. The apparent internal friction angle of a slurry with high concentration falls much lower than that with low concentration. This means that liquefaction of volcanic ash layer would be easily caused by the vibration like an earth quake or impact force of a slope failure in an area of active volcano even if in a little rain fall. Less