The deep-seated slope deformation at Encampadana, Andorra: Representation of morphologic features by numerical modelling
The deep-seated slope deformation at Encampadana, Andorra: Representation of morphologic features by numerical modelling
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DOI：
10.1016/j.enggeo.2005.11.008
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发表时间：
2006-03
影响因子：
7.4
通讯作者：
M. Hürlimann;A. Ledesma;J. Corominas;P. Prat
中科院分区：
文献类型：
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作者：
M. Hürlimann;A. Ledesma;J. Corominas;P. Prat
本研究旨在通过描述安道尔恩坎帕达纳斜坡的现场数据并使用简化的数值模型来改善对深层重力斜坡变形（DSGSD）的一般理解的一些方面。恩坎帕达纳 DSGSD 的现场调查揭示了两个主要的形态特征：靠近山顶的突出“地堑”和斜坡不同高度的反陡坡。地质数据显示，斜坡受到反模的影响，该反模由其外部的坚硬岩石和内部的更具延展性的材料（随后称为核心）组成。目前可用的信息无法评估影响斜坡的破坏机制。为了提高对边坡变形模式以及不同地质、结构和地貌特征影响的认识，通过界面单元模拟岩质边坡的节理模式进行了二维有限元建模。恩坎帕达纳斜坡位于一个河谷，该河谷受到更新世冰川的侵蚀以及随后退缩后谷壁的减压。这些阶段被实施到模型中以解释不断变化的压力历史。在建模过程中，重点关注三个不同因素的影响：(1) 地质不连续性，(2) 冰川侵蚀，(3) 斜坡中由黑色碳质页岩组成的延性核心。计算表明，尽管没有考虑构造应力的存在，但模拟该地点应力历史的分阶段方法是非常合适的。结果表明，不连续性的设置和冰川侵蚀产生了节理的开口、一些倾倒效应和反陡坡的发育。此外，韧性核心的结合产生了类似“地堑”的结构。所有这些特征都与现场观察到的形态一致。总之，数值模拟表明，即使使用非常有限的输入数据，也可以获得代表斜坡一般变形和观测到的现场特征的一些现实结果。
The present study is intended to improve some aspects referring to the general understanding of deep-seated gravitational slope deformations (DSGSD) by the description of field data from the Encampadana slope in Andorra, and using a simplified numerical modelling. The site investigation of the Encampadana DSGSD revealed two major morphologic features: a prominent “graben” close to the summit and counterscarps at different altitudes of the slope. The geological data showed that the slope is affected by an antiform consisting of hard resistant rocks in its outer parts and a more ductile material in its inner part, subsequently called core. Currently available information does not allow the appraisal of the failure mechanism affecting the slope. In order to improve the knowledge of both the pattern of the slope deformation and the influence of the different geologic, structural and geomorphologic features, 2D finite element modelling has been carried out simulating the joint pattern of the rock slope by interface elements. The Encampadana slope is located at a river valley that was subjected to erosion by Pleistocene glaciers plus the subsequent decompression of the valley walls after their retreat. These stages were implemented into the model to account for the evolving stress history. During modelling, focus was set on the effect of three different factors: (1) geological discontinuities, (2) glacier erosion, and (3) a ductile core in the slope consisting of black carbonaceous shales. The calculations showed that a staged approach for simulating the stress history of the site was very appropriate, although the presence of tectonic stresses was not incorporated. The results indicated that the discontinuity set and the glacier erosion generate an opening of the joints, some toppling-effects and the development of counterscarps. Moreover, the incorporation of a ductile core produced a “graben”-like structure. All these features are consistent with the morphology observed in the field. In conclusion, the numerical modelling indicates that some realistic results representing the general deformation of the slope and the observed field features can be achieved even with very limited input data.