The Role of Antecedent Conditions in Sinkhole Formation and Collapse Mechanisms

目的建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被长时间的干燥天气和暴雨削弱，以及这些条件的哪些组合可能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新出现的空洞上支撑地基时的稳定性的理解，并有助于预测已经开发的土地地区的天坑，这可以用来防止伤害和潜在的生命损失。-研究不同类型天坑形成的机制，例如历史上的白垩工作地的软化和破坏。了解这些故障所涉及的物理原理，可以为易受天坑影响地区的基础设施和结构的建筑法规和设计规范的补充提供信息。方法为了达到所列的目的，提出以下研究方法：-岩土工程桌研究，以确定样品提取的合适地点。这将利用现有文献以及英国地质调查局的天坑数据库来完成。-每年不同时间在选定地点采集黏土、白垩及其他岩石样本，并由英国地质调查局提供技术支援及钻探设备。这些样品将用于确定该地点的地面轮廓。-测试样品的岩土特性，例如含水量与强度之间的关系。这将在英国地质调查局提供的实验室设施中进行。-根据工地的岩土特性和地面轮廓，将制作典型易出现天坑的地层的比例模型，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。-将发展一种技术，以模拟不同的先决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。该技术将通过人工老化岩石与自然风化岩石的比较来验证。-制作不同含水量及老化情况的岩石及土壤模型。-这些模型将在离心机中进行测试，并使用图像分析技术（如颗粒图像测速法）研究和分类其失效机制，并进行计算反分析。-分析含水量、强度和老化条件之间的关系，并确定导致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.