The Role of Antecedent Conditions in Sinkhole Formation and Collapse Mechanisms

目的拟议研究的主要目的是：-探索易形成天坑的材料的岩土特性。这包括确定哪些特定的材料可能会因长时间的干旱天气和随后的暴雨而减弱，以及这些条件的哪些组合可能会导致天坑形成的可能性最大。实现这一目标将提高对这些材料在支撑地基以覆盖新出现的空洞时的稳定性的了解，并可以促进对已经开发土地的地区的天坑的预测，这可用于防止受伤和潜在的生命损失。-调查不同类型天坑形成的机制，例如历史上白垩岩的软化和破坏。对这些故障所涉及的物理问题的了解，可能有助于为易发生天坑的地区的基础设施和结构增加建筑法规和设计规范。方法为了达到所列出的目标，提出了以下研究方法：-岩土工作台研究，以确定合适的样本提取地点。这项工作将利用现有文献以及BGS天坑数据库进行。-将在一年中的不同时间从选定的地点采集粘土、白垩岩和其他岩石的样本，BGS将提供技术支持和钻探设备。这些样本将被用来确定场地的地面剖面。-将测试样本的岩土特性，例如含水率和强度之间的关系。这将在英国地质勘探局提供的实验室设施中进行。-根据场地的岩土性质和地面剖面，将制作典型的容易出现天坑的地层的比例尺模型，以便在离心机中进行测试，以产生典型的地应力。这将需要使用更多的样品或合成土壤材料。离心机是谢菲尔德大学现有的设备。-将开发一种技术来模拟不同前置条件对模型的老化影响。这可能需要新的设备，如干燥和加湿设备。这项技术将通过将人工老化的岩石与自然风化的岩石进行比较来验证。-将制作不同含水率和老化条件的岩土模型。-这些模型将在离心机中进行测试，并使用图像分析技术，如粒子图像测速仪，对其故障机理进行研究和分类，并进行计算反分析。-将分析含水率、强度和老化条件之间的关系，并确定产生最多天坑的关键组合。

AimsThe main aims of the proposed research are to:- Explore the geotechnical properties of materials susceptible to sinkhole formation. This includes determining which particular materials are likely to be weakened by long periods of dry weather followed by heavy rain, and which combinations of these conditions are likely to result in the greatest likelihood of sinkholes forming. Meeting this aim will improve understanding of the stability of these materials when supporting foundations over emerging cavities, and could facilitate the prediction of sinkholes in areas where land has already been developed, which could be used to prevent injury and potential loss of life. - Investigate the mechanisms involved in the development of different types of sinkhole, such as the softening and failure of historic chalk workings. An understanding of the physics involved in these failures could inform additions to building regulations and design codes for infrastructure and structures in areas susceptible to sinkholes. MethodIn order to meet the aims listed, the following research method is proposed:- A geotechnical desk study to identify suitable sites for sample extraction. This will be done using existing literature, as well as the BGS sinkhole database.- Samples of clay, chalk and other rocks will be taken from the selected locations at different times of the year, with technical support and drilling equipment to be provided by BGS. These samples will be used to determine a ground profile for the site.- The geotechnical properties of the samples, such as the relationship between water content and strength will be tested. This will be carried out in lab facilities provided by BGS. - Based on the geotechnical properties and ground profile of the site, scale models of typical sinkhole prone formations will be produced for testing in a centrifuge, to generate typical in-situ stresses. This will require the use of further samples or of synthetic soil material. The centrifuge is an existing facility at the University of Sheffield.- A technique for simulating aging effects of different antecedent conditions on the models will be developed. This may require new equipment such as drying and humidifying devices. The technique will be verified by comparison of artificially aged rocks with naturally weathered rocks. - Rock and soil models with different moisture contents, and ageing conditions will be produced. - These models will be tested in the centrifuge and their failure mechanisms studied and classified using image analysis techniques, such as particle image velocimetry, and calculated back analysis. - The relationship between water content, strength and ageing conditions will be analysed and the critical combination resulting in the most sinkholes determined.