Stress regime in compacted fills during wetting and drying cycles under laterally restrained conditions

健康和有弹性的基础设施（例如挡土墙和地下公用设施）为发达国家和发展中国家的经济成功提供了基本要素。由于包括英国在内的世界许多地方夏季炎热、冬季潮湿的环境迅速变化，这些基础设施面临着严重的压力。富含粘土的土壤（这是英国最常见的沉积物）对这些气候变化做出了反应，对基础设施的影响是严重的，特别是在财政方面的影响。该项目的目的是探索问题的一个具体方面，涉及到保留结构或填满粘土的刚性墙的性能。该项目的具体目标是：1)收集至少三种英国常见的不同土壤，并根据土壤水分特征、矿物学特征以及常规分类测试（如指数特性、粒度分布和压实特性）对其进行表征。2)建造尺寸为1mX1mX1m的模型试验箱，结合仪器测量吸力、体积含水量、小应变刚度、侧压力和变形。3)评估挡土墙结构（模型室的刚性墙代表挡土墙）的性能，该挡土墙填充了富含粘土的土壤（三种不同类型），并经受了潮湿（即在土壤表面产生典型降雨事件）和干燥（将土壤表面暴露在高温下，即英国记录的最高温度）条件的几个循环。4)纠正潜在的问题，如侧向压力的积累（如目标3中观察到的），通过修改粘土层的顶部表面，以限制或防止在湿期回填期间水的进入，并限制在干期土层的收缩。5)通过使用贝尔法斯特女王大学开发的最先进的应力路径单元进行元素测试，在微观水平上评估土壤的性能，用于研究经历湿润和干燥循环的土壤。6)通过使用邓迪大学现有的离心机测试进行调查，将目标3和4中概述的模型研究扩展到更实际的现场条件。7)在国际会议和期刊上传播研究结果。与这个项目相关的研究生将确保（在导师的指导下）所有的目标都能及时、高标准地实现。挡土墙或刚性墙的设计通常假定其周围的土壤是饱和的。这是一个非常简化的假设，因为土壤可能在第一次被压实，或者它可能经历干燥和湿润。由于土壤不饱和的复杂性和解释观测结果所需的科学知识，关于正在调查的主题的现有信息有限。导师有25年非饱和和饱和土的研究经验，有完善的实验室进行研究。希望本研究的结果能对目前设计挡土墙和刚性墙的方法产生影响。

Healthy and resilient infrastructure (for example retaining walls and buried utilities) provides the basic ingredients for economic success in developed and developing nations. This infrastructure is under severe strain due to a rapidly changing environment with hot summers and wet winters in many part of the world including the UK. Clay rich soils (which are the most common deposits in the UK) respond to these climate changes and the consequences on the infrastructure are severe, particularly in terms of financial implications. The aim of the project is to explore a specific aspect of the problem in relation to the performance of retaining structures or rigid walls backfilled with clay rich soils. The specific objectives of the projects are:1) Collection of at least three different soils commonly found in the UK and characterization of them in terms of soil water characteristics, mineralogy together with the routine classification tests such as index properties, particle size distributions and compaction characteristics.2) Construction of a model testing chamber with dimensions of 1mX1mX1m combined with instrumentation to measure suction, volumetric water content, small strain stiffness, lateral pressure and deformation.3) Evaluation of the performance of the retaining structure (the rigid wall of the model chamber represents a retaining wall) back filled with clay rich soils (three different types) and subjected to several cycles of wet (i.e. creating a typical rainfall event on the soil surface) and dry (exposing the soil surface to elevated temperature i.e. the maximum recorded in the UK) conditions.4) Rectification of potential issues such as build-up of lateral pressure (as observed in Objective 3) by modifying the top surface of the clay bed in such a way to limit or prevent ingress of water during backfill in wet periods and to limit the shrinkage of the soil bed during dry periods.5) Assessment of soil performance at micro level by performing element testing using a state of the art stress path cell developed at Queen University Belfast for investigation soils undergoing wetting and drying cycles.6) Extending the model study as outlined in Objectives 3 and 4 to more realistic in-situ conditions by performing investigations using centrifuge testing available at the University of Dundee.7) Dissemination of the findings at international conferences and in journals. The postgraduate student associated with this project will ensure (with guidance from the supervisor) that all of the objectives are achieved in a timely manner and to a good standard. Retaining structures or rigid walls are normally designed by assuming the soils surrounding them are saturated. It is a very simplified assumption as the soil may have been compacted in the first instance or it may undergo drying and wetting. Existing information on the topic under investigation is limited due to complexity of the soil being unsaturated and the required scientific knowledge in interpreting the observations. The supervisor has 25 years of experience in carrying of investigations on unsaturated and saturated soils and a well-developed laboratory to conduct the investigations. It is hoped that the outcome from the research will have an impact on the current methods adopted for designing retaining structures and rigid walls.