日本大谷滑坡疤痕完全和部分饱和泥石流孔隙水压力的实地监测

IF 2.8 2区 地球科学 Q2 GEOGRAPHY, PHYSICAL Earth Surface Dynamics Pub Date : 2024-01-09 DOI:10.5194/esurf-12-67-2024
Shunsuke Oya, Fumitoshi Imaizumi, Shoki Takayama
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引用次数: 0

摘要

摘要泥石流的特征(如流动性、沉积物浓度、侵蚀和沉积)取决于泥石流中的孔隙水压力。因此,了解泥石流中孔隙水压力的大小对于改进泥石流缓解措施至关重要。值得注意的是,由于缺乏数据,以前人们尚未了解部分饱和流(其上部包含非饱和层)中的孔隙水压力。通过对日本中部大谷滑坡疤痕进行监测,我们获得了四次泥石流事件中完全饱和流和部分饱和流的孔隙水压力数据。在一些部分和完全饱和的泥石流中,河床处的孔隙水压力超过了清水的静水压力。利用多个深度的水压传感器监测到的泥石流下部孔隙水压力的深度梯度通常高于从河床到泥石流表面的孔隙水压力的深度平均梯度。部分饱和泥石流上部的孔隙水压力梯度较低,可能是由于泥石流未饱和导致静水压力较低。巴格诺尔德数、萨维奇数和摩擦力数表明,摩擦力在部分饱和泥石流中占主导地位。在部分饱和的涌流下部观察到过大的孔隙水压力。过大的孔隙水压力可能是由间隙水收缩产生的,并由于泥石流中较低的水力扩散性而得以维持。完全饱和泥石流河床处的孔隙水压力一般与清水的静水压力相近,而一些饱和涌流的孔隙水压力高于静水压力。利用无人驾驶航空飞行器(UAV-SfM)的运动结构技术和延时摄影机的监测对泥石流的移动距离进行了研究,在一次高强度降雨事件中,尽管泥石流中的孔隙水压力并不高,但泥石流的移动距离却很长。我们的结论是,过高的孔隙水压力存在于许多泥石流涌中,是泥石流涌行为的一个重要机制。
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Field monitoring of pore water pressure in fully and partly saturated debris flows at Ohya landslide scar, Japan
Abstract. The characteristics of debris flows (e.g., mobility, sediment concentration, erosion, and deposition of sediment) are dependent on the pore water pressure in the flows. Therefore, understanding the magnitude of pore water pressure in debris flows is essential for improving debris flow mitigation measures. Notably, the pore water pressure in a partly saturated flow, which contains an unsaturated layer in its upper part, has not been previously understood due to a lack of data. The monitoring performed in Ohya landslide scar, central Japan, allowed us to obtain the data on the pore water pressure in fully and partly saturated flows during four debris flow events. In some partly and fully saturated debris flows, the pore water pressure at the channel bed exceeded the hydrostatic pressure of clean water. The depth gradient of the pore water pressure in the lower part of the flow, monitored using water pressure sensors at multiple depths, was generally higher than the depth-averaged gradient of the pore water pressure from the channel bed to the surface of the flow. The low gradient of the pore water pressure in the upper part of partly saturated debris flows may be affected by the low hydrostatic pressure due to unsaturation of the flow. Bagnold number, Savage number, and friction number indicated that frictional force dominated in the partly saturated debris flows. Excess pore water pressure was observed in the lower part of partly saturated surges. The excess pore water pressure may have been generated by the contraction of interstitial water and have been maintained due to low hydraulic diffusivity in debris flows. The pore water pressure at the channel bed of fully saturated flow was generally similar to the hydrostatic pressure of clean water, while some saturated surges portrayed higher pore water pressure than the hydrostatic pressure. The travel distance of debris flows, investigated by the structure-from-motion technique using uncrewed aerial vehicle (UAV-SfM) and the monitoring of time-lapse cameras, was long during a rainfall event with high intensity even though the pore water pressure in the flow was not significantly high. We conclude that the excess pore water pressure is present in many debris flow surges and an important mechanism in debris flow surge behaviors.
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来源期刊
Earth Surface Dynamics
Earth Surface Dynamics GEOGRAPHY, PHYSICALGEOSCIENCES, MULTIDISCI-GEOSCIENCES, MULTIDISCIPLINARY
CiteScore
5.40
自引率
5.90%
发文量
56
审稿时长
20 weeks
期刊介绍: Earth Surface Dynamics (ESurf) is an international scientific journal dedicated to the publication and discussion of high-quality research on the physical, chemical, and biological processes shaping Earth''s surface and their interactions on all scales.
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