Braced excavations: what about the corners?

支撑挖掘：拐角处怎么样？

• 批准号: EP/X024849/1
• 负责人: Charles Augarde
• 金额: $ 59.98万
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FX024849%2F1
• 关键词: Braced; excavations; what; about; corners

When a new metro station or a deep basement are to be constructed in a city, a large hole in the ground is needed. The hole needs to be safe to work in and to allow access and very often the chosen solution is to support the sides of the large hole with a braced embedded retaining wall. These are substantial pieces of temporary works of considerable cost. Recent examples are the 230 long by 24 m wide by 23m deep excavation for the new Crossrail station at Paddington in London. An important feature of this form of construction is large props that span between the walls, to hold them up. For those tasked with designing the prop size, location, number and the walls the key issues are prediction of ground movements adjacent to the excavation (which could negatively affect buildings) and propping forces (so that the right props can be used and while guidance exists for designers in some recent publications produced by the UK construction information organisation, CIRIA, coverage of the behaviour at excavation corners as regards both design issues is poor. There is substantial published research on the computational modelling of braced excavations but only in two-dimensions (i.e. s slice through a long wall), some of it validated against field data, however accounting for 3D effects as required for the analysis of corners is rare and insubstantial. Improving our understanding of the behaviour of these corners and how it is affected by soil behaviour, system stiffness, and prop loading will lead to (a) greater economy in propping schemes and (b) more certainty in the prediction of ground movements adjacent to corners, potentially reducing the accommodation works required to prevent damage to adjacent structures. The programme of research proposed here comprises complex computational simulations of the construction of a braced excavation, taking into account differences in geometry, materials and sequences. The problem can only be properly tackled using a 3D model (unlike many other problems in geotechnical engineering) however even today, the computational tools we use struggle to deliver results quickly when we try to model in 3D. So, in this proposal we will be using a clever method where "reduced order models", (ROMs) will be made, using results from a relatively small set of the complex 3D models. A ROM is much easier to use and is generated by manipulation of a limited number of the high fidelity 3D simulations. From these ROMs we will derive results and prepare guidance for engineers designing braced excavations which will enable cheaper and simpler schemes to be used.The researchers on the project come from Durham and Dundee Universities and are supported by a Project Oversight Group comprising key figures from the UK industry.

当一个城市要修建一个新的地铁站或一个很深的地下室时，需要在地面上打一个大洞。这个洞需要是安全的，才能进入，通常选择的解决方案是用支撑嵌入的挡土墙支撑大洞的两侧。这些都是耗资巨大的临时性工程。最近的例子是伦敦帕丁顿新的Crossail车站的230长24米宽23米深的挖掘。这种建筑形式的一个重要特征是跨越墙壁之间的大型支柱，以支撑它们。对于那些负责设计道具大小、位置、数量和墙壁的人来说，关键问题是预测挖掘附近的地面运动(这可能会对建筑物产生负面影响)和支撑力(以便可以使用正确的道具)，尽管英国建筑信息组织CIRIA最近出版的一些出版物为设计师提供了指导，但在这两个设计问题上，对挖掘角落的行为的报道很少。已有大量已发表的关于支撑开挖计算模型的研究，但仅限于二维(即S切片穿过长墙)，其中一些研究通过现场数据进行了验证，然而考虑拐角分析所需的三维效应的研究很少，而且缺乏实质性。改善我们对这些拐角的特性以及它如何受土壤特性、系统刚度和支柱载荷影响的了解，将导致(A)在支撑方案方面更经济，(B)在预测拐角附近的地面移动时更具确定性，从而潜在地减少防止对邻近建筑物造成损害所需的通融工程。这里提出的研究方案包括复杂的计算模拟，考虑到几何、材料和顺序的差异，对支撑开挖的施工进行模拟。只有使用3D模型才能正确地解决这个问题(与岩土工程中的许多其他问题不同)。然而，即使在今天，当我们尝试在3D中建模时，我们使用的计算工具仍然难以快速交付结果。因此，在这项提案中，我们将使用一种巧妙的方法，使用相对较小的复杂3D模型集的结果来制作“降阶模型”(ROMs)。只读存储器更易于使用，并且是通过操纵有限数量的高保真3D模拟来生成的。我们将从这些只读光盘中得出结果，并为工程师设计支撑挖掘提供指导，这将使我们能够使用更便宜、更简单的方案。该项目的研究人员来自达勒姆大学和邓迪大学，并得到了一个由英国行业关键人物组成的项目监督小组的支持。