Observations and modelling of soil slip-debris flow initiation processes in pyroclastic deposits: the Sarno 1998 event
Observations and modelling of soil slip-debris flow initiation processes in pyroclastic deposits: the Sarno 1998 event
复制标题
火山碎屑沉积物中土壤滑移-泥石流引发过程的观测和模拟：Sarno 1998 事件
DOI：
10.5194/nhess-3-53-2003
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发表时间：
2003
影响因子：
4.6
通讯作者：
P. Negro
中科院分区：
文献类型：
--
作者：
G. Crosta;P. Negro
抽象的。坎帕尼亚亚平宁大片地区的火山碎屑土经常发生不稳定现象。本研究分析了1998年5月5日和6日发生的事件，该事件影响了意大利南部坎帕尼亚的Pizzo d‘Alvano。400多个影响浅层火山碎屑沉积的滑坡是由强烈和长期的降雨引发的，但不是极端的降雨。滑坡影响了覆盖在陡峭的钙质山脊上的火山碎屑沉积，是土壤滑动泥石流和快速泥石流。大约30条主要河道被水流冲刷得很深，水流到达冲积扇，在山前地区沉积了多达40万立方米的物质。大约75%的滑坡与形态不连续有关，如石灰岩悬崖和道路。滑动面位于火山碎屑盖层内，通常位于浮石层的底部。已通过实验室和现场试验完成了火山碎屑矿床的岩土工程特征。对渗流过程进行了数值模拟，并对四个简化模型进行了稳定性分析，这些简化模型代表了在源区观测到的不同环境。渗流模拟显示，随着4月28日至5月5日的降雨事件，浮石层中形成了孔压脉冲，并与地层不连续面相对应地局部增加了孔压。数值模拟为稳定性分析提供了孔隙压力值，并指出了发生地层或形态不连续的关键条件。这项研究排除了地下水流从下面的基岩流向火山碎屑盖层而不会发生不稳定的需要。
Abstract. Pyroclastic soils mantling a wide area of the Campanian Apennines are subjected to recurrent instability phenomena. This study analyses the 5 and 6 May 1998 event which affected the Pizzo d’Alvano (Campania, southern Italy). More than 400 slides affecting shallow pyroclastic deposits were triggered by intense and prolonged but not extreme rainfall. Landslides affected the pyroclastic deposits that cover the steep calcareous ridges and are soil slip-debris flows and rapid mudflows. About 30 main channels were deeply scoured by flows which reached the alluvial fans depositing up to 400 000 m3 of material in the piedmont areas. About 75% of the landslides are associated with morphological discontinuities such as limestone cliffs and roads. The sliding surface is located within the pyroclastic cover, generally at the base of a pumice layer. Geotechnical characterisation of pyroclastic deposits has been accomplished by laboratory and in situ tests. Numerical modelling of seepage processes and stability analyses have been run on four simplified models representing different settings observed at the source areas. Seepage modelling showed the formation of pore pressure pulses in pumice layers and the localised increase of pore pressure in correspondence of stratigraphic discontinuities as response to the rainfall event registered between 28 April and 5 May. Numerical modelling provided pore pressure values for stability analyses and pointed out critical conditions where stratigraphic or morphological discontinuities occur. This study excludes the need of a groundwater flow from the underlying bedrock toward the pyroclastic cover for instabilities to occur.