Weathering profile of non-welded ignimbrite and the water infiltration behavior within it in relation to the generation of shallow landslides
Weathering profile of non-welded ignimbrite and the water infiltration behavior within it in relation to the generation of shallow landslides
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DOI：
10.1016/j.enggeo.2004.12.008
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发表时间：
2005-05
影响因子：
7.4
通讯作者：
M. Chigira;O. Yokoyama
中科院分区：
文献类型：
--
作者：
M. Chigira;O. Yokoyama
根据对日本九州南部伊藤熔结凝灰岩的研究，发现非熔结凝灰岩降雨诱发浅层滑坡的机制是一种特殊类型的风化剖面和水渗透通过该剖面的行为。熔结凝灰岩的主要成分流纹质火山玻璃首先水化溶解，形成埃洛石。近地表的埃洛石在水的渗透作用下通过熔结凝灰岩运移，堵塞在空隙中形成粘土带。整个风化剖面的吸力监测表明，向下渗透的水被破坏一次由一个区域的渗透性较低的粘土带，并再次在风化前沿。这种前端的破坏是由毛细屏障效应引起的，毛细屏障效应是由较细的风化物质覆盖在较粗的新鲜物质上的结构引起的。这导致了一个明确的风化锋，特别是在水通量与锋平行的斜坡下，而锋在脊顶下是过渡性的，锋几乎是水平的，水通量与锋垂直。雨水的渗入增加了风化物质的重量，降低了物质内部的吸力，这是非焊接熔结凝灰岩浅层滑坡的最终触发因素;多年的长期风化提供了滑动材料。
The mechanism underlying rain-induced shallow landslides of non-welded ignimbrite is found to be a special type of weathering profile and the behavior of water infiltrating through that profile, according to our study of Ito ignimbrite in southern Kyushu, Japan. Rhyolitic volcanic glass, the primary component of ignimbrite, is first hydrated and dissolved, forming halloysite. Halloysite near ground surface is then transported through the ignimbrite by infiltrating water and becomes clogged in interstices to form clay bands. Suction monitoring across a weathering profile indicated that downward infiltration of water is disrupted once by a zone of less-permeable clay bands and again at the weathering front. This disruption at the front is caused by a capillary barrier effect caused by the structure where finer, weathered material overlies coarser, fresh material. This results in a well-defined weathering front, particularly beneath a slope where water flux is parallel to the front, whereas the front is transitional beneath a ridge top where the front is nearly horizontal and the water flux is normal to the front. Infiltrating water from rain increases the weight of weathered material and decreases the suction within the material, which is the final trigger of a shallow landslide of non-welded ignimbrite; long-term weathering, which proceeds on the order of years, provides slide material.