Engineering geology of landslides on the volcanic island of Montserrat, West Indies
Engineering geology of landslides on the volcanic island of Montserrat, West Indies
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西印度群岛蒙特塞拉特火山岛上滑坡的工程地质学
DOI：
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发表时间：
2007
影响因子：
1.4
通讯作者：
Laurance Donnelly
中科院分区：
文献类型：
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作者：
Laurance Donnelly
蒙特塞拉特岛是英国在西印度群岛（加勒比海）的附属岛屿，在那里观察到了不同类型的山崩。位于该岛南部的苏弗里埃火山在休眠了大约400年之后，自1995年以来一直处于几乎持续不断的火山活动状态。最引人注目的，独特的“滑坡”发生在英语火山口内的喷出，扩大，安山质熔岩圆顶。福尔斯、倾倒和滑坡是由于穹顶过于陡峭，随后重力坍塌造成的。有时，这些故障产生白炽岩石雪崩，这可能最终进入火山碎屑流，浪涌和块和灰流。这些是高度破坏性的热密度流，并加速下坡，受到地形和放射状排水通道（称为“ghauts”）的控制，这些通道已被切割在火山的侧面。这些流动在火山的上、中两侧沉积了大量炽热的火山碎屑。火山碎屑和空气沉降物在暴雨期间的侵蚀导致了火山泥流（印度尼西亚语中描述火山泥流的术语）的产生。从1999年1月到2006年，已经观察和记录了40多个火山泥流。这些都与飓风和降雨率增加相吻合，通常在6月至11月之间。拉哈尔沉积物通常由包括巨砾在内的粒状物质组成，已经填充了许多河谷。特别是Belham山谷的下游地区已经被填满，这导致排水集水区堵塞，基础设施和房屋被掩埋。在目前的火山活动区域之外，也观察到了山体滑坡，尽管它们的重要性并不总是得到承认，因为它们的调查可能经常被忽视，因为火山本身发生了更壮观的戏剧性事件。山体滑坡包括沿海山体滑坡和内陆山体滑坡，它们是由地震事件（例如构造地震和火山岩浆地震）和气候事件（例如暴雨和飓风）共同产生的。厚的热带风化红土（风化层）的存在促进了滑坡的产生，这些红土在中陡坡、高起伏地区、强风化火山基岩上发育。土壤和地形都会影响排水和地下水流动，这反过来又会影响斜坡的稳定性，导致首次斜坡破坏的开始和更老、更退化的滑坡的重新激活。除了自然过程外，人类活动（例如道路建设、挖掘斜坡或倾倒废物装载斜坡）也会造成山体滑坡。本文件的目的是记录并提请注意蒙特塞拉特山崩的原因和类型，特别是扩大的熔岩穹丘、贝尔汉姆谷火山泥流和蒙特塞拉特火山观测站的泥石流。本文提供了一个工程地质的角度来看，已观察到的蒙特塞拉特的滑坡地质灾害。
Different types of landslides have been observed on Montserrat, a British dependent island in the (Caribbean) West Indies. The Soufrière Hills volcano, situated in the southern part of this island, has been in a state of almost continuous volcanic activity since 1995, after being dormant for about 400 years. The most dramatic, distinct ‘landslides’ occur on the extrusive, expanding, andesitic lava dome within English Crater. Falls, topples and slides are caused by the over-steepening of the dome followed by its gravitational collapse. On occasions, these failures generate incandescent rock avalanches, which may ultimately transgress into pyroclastic flows, surges and block & ash flows. These are highly destructive, hot, density currents and accelerate down-slope, controlled by the topography and radial drainage channels (known as ‘ghauts’), which have been incised on the flanks of the volcano. These flows have deposited huge volumes of incandescent pyroclastic debris on the upper and middle flanks of the volcano. The erosion of the pyroclastic debris and air-fall deposits, during rainstorms, has resulted in the generation of lahars (an Indonesian term to describe a volcanic mudflow). Well over 40 lahars have been observed and recorded, from January 1999 to 2006. These coincided with hurricanes and increased rainfall rates usually between the months of June and November. The lahar deposits, typically consisting of granular material including boulders, have infilled many of the river valleys. The lower reaches of the Belham valley in particular has been infilled, and this has resulted in the choking of drainage catchment areas and the burial of infrastructure and houses. Beyond the area of current volcanic activity landslides have also been observed, although their significance has not always been recognized, as their investigation may often be overlooked because of the more spectacular dramatic events on the volcano itself. The landslides include both coastal and inland landslides, which are generated by a combination of seismic events (such as tectonic and volcano-magmatic earthquakes) and climatic events (such as rainstorm and hurricanes). Landslide generation is facilitated by the presence of thick, tropical weathered laterite soils (regolith) that develop on moderate to steep slopes, in areas of high relief, on intensely weathered volcanic bedrock. Both soils and topography influence drainage and groundwater flows, which in turn affect the stability ofslopes, causing the initiation of first time slope failures and the reactivation of older, more degraded landslides. In addition to natural processes, the activities of man (such as road building, the digging into slopes or the loading of slopes by tipping waste) have also caused landslides to develop. The objectives of this paper are to document and draw attention to the causes and types of landslides on Montserrat with particular reference to the expanding lava dome, the Belham valley lahars and the Montserrat Volcano Observatory (MVO) debris slide. This paper provides an engineering geological perspective on the landslide geohazards that have been observed on Montserrat.