Testing the suitability of frictional behaviour for pyroclastic flow simulation by comparison with a well-constrained eruption at Tungurahua volcano (Ecuador)
Testing the suitability of frictional behaviour for pyroclastic flow simulation by comparison with a well-constrained eruption at Tungurahua volcano (Ecuador)
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通过与通古拉瓦火山（厄瓜多尔）良好约束的喷发进行比较，测试火山碎屑流模拟中摩擦行为的适用性
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发表时间：
2009
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通讯作者：
D. Barba
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作者：
K. Kelfoun;P. Samaniego;P. Palacios;D. Barba
我们使用一个监测良好的喷发通古拉瓦火山测试的有效性的摩擦行为，也被称为莫尔-库仑，这是一般用于地球物理流动建模。我们表明，摩擦法是不适合在通古拉瓦火山碎屑流的模拟。根据这一定律，模拟流动的纵向形状是一个薄的楔形材料，从前端不切实际的厚度（<<1 mm）逐渐通过几百米，到几十厘米。模拟沉积物形成堆积在火山脚下的堆积物，与天然火山碎屑沉积物相比，更类似于沙堆。最后，用摩擦流变学模拟的流动没有被排水系统引导，而是影响火山的所有侧翼。此外，它们的速度可以超过150 m s-1，使火山碎屑流在山谷的弯曲处穿过河间，影响实际上不会受到影响的地区，并留下实际上会被覆盖的清晰下游地区。相反，一个简单的经验法则，一个恒定的延迟应力（即屈服强度），只涉及一个自由参数，似乎是更好地适应建模火山碎屑流。对Socompa碎片雪崩的模拟得出了类似的结论（Kelfoun和Druitt，J Geophys Res 110：B12202，2005年）。
We use a well-monitored eruption of Tungurahua volcano to test the validity of the frictional behaviour, also called Mohr–Coulomb, which is generally used in geophysical flow modelling. We show that the frictional law is not appropriate for the simulation of pyroclastic flows at Tungurahua. With this law, the longitudinal shape of the simulated flows is a thin wedge of material progressively passing, over several hundreds of metres, from an unrealistic thickness at the front (<<1 mm) to some tens of centimetres. Simulated deposits form piles which accumulate at the foot of the volcano and are more similar to sand piles than natural pyroclastic deposits. Finally, flows simulated with a frictional rheology are not channelised by the drainage system, but affect all the flanks of the volcano. In addition, their velocity can exceed 150 m s−1, allowing pyroclastic flows to cross interfluves at bends in the valley, affecting areas that would not have been affected in reality and leaving clear downstream areas that would be covered in reality. Instead, a simple empirical law, a constant retarding stress (i.e. a yield strength), involving only one free parameter, appears to be much better adapted for modelling pyroclastic flows. A similar conclusion was drawn for the Socompa debris avalanche simulation (Kelfoun and Druitt, J Geophys Res 110:B12202, 2005).