An investigation into open-system pingos in Canada as an analogue to drift-filled hollows in London

EPSRC：Jennifer Scoular：EP/L016826/1A伦敦工程项目的主要危险是被称为漂移充填空洞(DFH)的地质特征。它们是典型的锥形凹陷，位于充满沙子和砾石的基岩中。DFH的深度可达75米，宽度可达90至475米。他们在伦敦的许多小型和大型工程项目中都遇到过，包括泰晤士河李隧道、Crossail、泰晤士河环主干道和巴特西发电站的建设。这些东铁隧道往往含有水，因此在隧道施工时会渗水，并导致不均匀的沉降。由于这些特征的位置只在工程项目中被发现，因此人们对这些特征在伦敦的分布情况知之甚少。伦敦的工程师们并不完全了解这些特征是如何形成的。一种假设是，这些特征是在历史上的冰川时期形成的，就是平戈斯。平果是位于寒冷地区的圆顶形土丘，以永久冻土为特征。穹顶的形状是由覆盖着土壤的冰芯形成的。假设是，当这些地物在伦敦融化时，它们被冰川融化水注入的河流冲走，形成了我们今天观察到的DFH。我们可以观察到现代披哥的地区是加拿大的西北地区和育空地区。我们提出了田野调查和遥感方法来验证这一假设。首先，直接检查Pingo的生长和活动Pingo的特征，然后检查那些已经崩溃的Pingo。这将使我们能够更好地了解它们是否可能在过去在伦敦形成，如果加拿大倒塌的平果与伦敦的DFH有任何相似之处。其次，我们将利用包括航空摄影、卫星图像和数字高程模型在内的遥感数据，制作北极平果位置的数字地图。这些位置可能会提供影响它们形成地点的因素的线索，包括冰层的水源和它们在下面形成的土壤类型。通过这些观察，我们的目标是能够得出伦敦的DFH是否可能形成为PINGO，如果是的话，什么因素影响它们的位置，以提高我们对伦敦哪里可以找到它们的了解。由于伦敦目前正在进行一项大型隧道工程--泰晤士河隧道，也被称为伦敦的“超级下水道”，了解这些危险地物的位置是非常重要的。

EPSRC : Jennifer Scoular : EP/L016826/1A major hazard to engineering projects in London are geological features known as drift-filled hollows (DFHs). They are typically cone-shaped depressions in the bedrock filled with sand and gravel. DFHs can be up to 75 m deep and 90 to 475 m wide. They have been encountered on many small- and large-scale engineering projects in London, including the Thames Tideway Lee Tunnel, Crossrail, the Thames Water Ring Main and Battersea Power Station construction. These DFHs often contain water, therefore leading to water ingress whilst tunnelling as well as uneven settlement. The distribution of these features across London is poorly understood, due to their locations only being discovered during engineering projects.Engineers in London do not fully understand how these features formed. One hypothesis is that these features formed during historic glacial periods as pingos. Pingos are dome shaped mounds in cold regions characterised by permafrost. The dome shape is formed by an ice core, which is overlain with soil. The hypothesis is that, when these features melted in London, they were scoured out by rivers fed by glacial meltwater forming the DFHs we observe today. Regions where we can observe modern pingos is the Northwest Territories and Yukon territory of Canada.We propose both a fieldwork and remote sensing approach to test this hypothesis. Firstly, a direct inspection of pingo growth and characteristics of active pingos, followed by inspections of those that have collapsed. This will enable us to better understand if they could have formed in London in the past if the collapsed pingos in Canada share any characteristics with DFHs in London. Secondly, we will use remote sensing data including aerial photography, satellite imagery and digital elevation models, to make a digital map of the location of pingos in the Arctic. The locations may provide clues on factors that effect where they form, including water source for the ice and the type of soil they form under.From these observations, we aim to be able to conclude whether DFHs in London could have formed as pingos and if so, what factors affect their location to improve our knowledge of where to find them in London. With a major tunnelling project currently ongoing in London, the Thames Tideway Tunnel, also known as London's 'super-sewer', knowledge about the location of these hazardous features is of great importance.