Dynamics of an Active Earthflow Inferred From Surface Wave Monitoring
Dynamics of an Active Earthflow Inferred From Surface Wave Monitoring
复制标题
从表面波监测推断的活跃地流动力学
DOI：
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Gabriela Squarzoni
中科院分区：
文献类型：
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作者：
L. Bertello;M. Berti;S. Castellaro;Gabriela Squarzoni
泥石流是富含粘土的缓慢移动的滑坡，受到周期性的加速度。在快速运动阶段，大多数土流表现出从固态到类流体状态的行为变化。虽然这种行为已经在现场得到了广泛的记录，但导致土流快速加速的机制仍然知之甚少。一些研究认为，土流本质上表现为库仑塑性固体，将流动状外观归因于分布的内部剪切;其他人认为这些滑坡可以被视为粘性流体，指出材料通过增加其水分含量而经历相变。目前可用于支持这些不同发现的数据很少。在这项研究中，我们提出的周期性和连续测量的瑞利波速度进行了活跃的泥石流位于北方亚平宁山脉的意大利。我们的数据表明，材料经历了显着的变化，在剪切刚度和不排水强度在快速运动。特别是，该材料表现出的瑞利波速度的大幅下降，因为土流加速，然后由一个缓慢的返回到干扰前的瑞利速度作为滑坡减速。涌浪后不久，土流物质非常软，估计的重量含水量高于液限。在接下来的几个月里，剪切刚度逐渐增加，含水量降低到塑性极限以下的非线性趋势典型的固结过程。这些数据表明，土流转化为粘性流体的软化材料和水夹带。
Earthflows are clay‐rich, slow‐moving landslides subjected to periodic accelerations. During the stage of rapid movement, most earthflows exhibit a change in behavior from a solid to a fluid‐like state. Although this behavior has been extensively documented in the field, the mechanism leading to the rapid acceleration of earthflows is still poorly understood. Some studies suggest that earthflows essentially behave as Coulomb plastic solids, attributing the flow‐like appearance to distributed internal shearing; others believe that these landslides can be treated as viscous fluids, pointing out that the material undergoes a phase transition by increasing its moisture content. Minimal data are currently available to support these different findings. In this study, we present the results of periodic and continuous measurements of Rayleigh wave velocity carried out in an active earthflow located in the northern Apennines of Italy. Our data indicate that the material undergoes significant changes in shear stiffness and undrained strength during rapid movements. In particular, the material exhibits a substantial drop of Rayleigh wave velocity as the earthflow accelerates, followed by a slow return to predisturbance Rayleigh velocities as the landslide decelerates. Soon after a surge, the earthflow material is extremely soft and the estimated gravimetric water content is above the liquid limit. In the following months, the shear stiffness gradually increases and the water content decreases to the plastic limit following a nonlinear trend typical of a consolidation process. These data demonstrate that the earthflow transforms into a viscous fluid by softening of the material and by water entrainment.