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事业)为发达国家和发展中国家的经济成功提供了基本要素。由于环境快速变化，包括英国在内的世界许多地区夏季炎热，冬季潮湿，这一基础设施面临着严重的压力。富含粘土的土壤(这是英国最常见的矿藏)对这些气候变化做出了反应，对基础设施的影响是严重的，特别是在财务影响方面。该项目的目的是探索与用富含粘土的土壤回填的挡土结构或刚性墙的性能有关的问题的一个特定方面。这些项目的具体目标是：1)收集至少三种在英国常见的不同土壤，并根据土壤水分特性、矿物学和常规分类试验，如指数特性、颗粒分布和压实特性，对它们进行表征。2)建造一个尺寸为1mx1mx1m的模型试验室，并结合仪器测量吸力、体积含水率、小应变硬度、侧向压力和变形。3)评估挡土墙结构(模型箱体的刚性墙代表挡土墙)的性能，后填满富含粘土的土壤(三种不同类型)，并经历几个周期的湿(即在土壤表面产生典型的降雨事件)和干(使土壤表面暴露在高温下，即英国有记录的最高温度)条件。4)纠正潜在的问题，例如侧压力的累积(如在目标3中观察到的)，方法是修改粘土层的顶面以限制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微观水平的元素测试来评估土壤性能，以研究经历干湿循环的土壤。6)通过使用邓迪大学提供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现实的现场条件。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达到良好的标准。挡土结构或刚性墙的设计通常假定其周围的土体是饱和的。这是一个非常简单的假设，因为土壤可能在一开始就被压实了，或者可能经历了干燥和潮湿。由于土壤不饱和的复杂性以及解释观测所需的科学知识，关于正在调查的专题的现有信息有限。该主管在进行非饱和和饱和土壤的勘测方面有25年的经验，并拥有完善的实验室进行勘测。希望研究结果能对目前采用的挡土结构和刚性墙设计方法产生一定的影响。

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.