AN EXPERIMENTAL AND ANALYTICAL STUDY OF DRY-STONE RETAINING WALLS

干石墙是由小心堆积的碎石块形成的，不使用砂浆。干石墙遍布世界各地，形成了英国许多地区的鲜明特色，包括科茨沃尔德，皮克区和湖区。干砌石挡土墙是一种用于支撑公路、铁路和运河路堑和护坡的工程结构。墙通常约为0.6米厚，由砌石面和后面的碎石组成。它们大多建于19世纪和20世纪初。仅在英国的公路网上就有大约9000公里的这些墙，估计重置价值超过10亿美元。虽然老化的墙仍然表现良好，但它们的状况不断恶化，偶尔会突然倒塌，这是公路维修当局面临的一个主要问题。这些墙在荷载下的实际行为以及防止倒塌的安全因素是什么，都是不确定的。由于目前对包括三维效应在内的真实的倒塌机制缺乏了解，加上现代设计规范所要求的安全因素以及土壤性质、墙体尺寸、地下水条件和荷载等设计参数的不确定性，导致不必要地更换令人满意的墙壁，以及未能识别有即将倒塌危险的墙壁。即使干燥-与更现代的土壤保持方法（例如使用当地材料结合自由排水和灵活的结构）相比，石墙具有明显的优势，但工程的不确定性使得干石砌体很少有新的和替代的建筑。对令人满意的墙进行不必要的更换，通常是用混凝土结构，导致与建筑有关的高成本、交通中断、增加财产或生命损害的风险以及潜在的不利环境影响。鉴于自170多年前进行的有限研究以来，尚未对干石挡土墙进行过重大的实验研究，因此目前对干石挡土墙行为的真实的机制缺乏了解也许并不令人惊讶。由此导致的缺乏有关干砌石挡土墙行为的直接定量数据不仅是其本身的问题，而且还阻碍了现代计算机数值分析的验证。干砌石挡土墙在维修和新建工程中的使用增加，以及现有库存的使用寿命延长，只有在正确、有效、基于理论的理解这些结构如何工作的情况下才能实现。以及开发适用于现代工程环境的适当设计方法。目前阻碍干砌石挡土墙有效和准确评估的两个主要不确定因素是膨胀和壁厚。拟议的研究的目的是开发一个更好地了解这两个关键问题，通过实验研究结合参数化三维离散元分析，并进一步发展极限平衡分析方法的设计和分析现有的干石挡土墙。

Dry-stone walls are formed by carefully stacking blocks of stone rubble, without the use of mortar. Found throughout the world, dry-stone walls form the distinctive character of many areas of the UK, including the Cotswolds, Peak District and Lake District. Dry-stone retaining walls are engineering structures used to support road, railway and canal cuttings and embankments. The walls are commonly about 0.6m thick and are comprised of a bonded masonry face with stacked rubble stone behind. They were mostly built during the 19th and early 20th centuries. There are about 9000 km of these walls along the UK road network alone, having an estimated replacement value in excess of 1 billion. Though the ageing stock of walls is still performing very well, their deteriorating condition and occasional sudden collapse is a major problem for highway maintenance authorities.There is uncertainty about how these walls actually behave under load and what the factors of safety against collapse are. This current lack of understanding of real collapse mechanisms including three-dimensional effects, combined with the factors of safety required by modern design codes and uncertainties over design parameters such as soil properties, wall dimensions, groundwater conditions and loading, leads to the unnecessary replacement of satisfactory walls and the failure to identify walls that are in danger of imminent collapse.Even though dry-stone walls have distinct advantages over more modern earth retention methods (such as the use of local materials combined with a free-draining and flexible structure), the engineering uncertainties are such that new and replacement construction is rarely in dry-stone masonry. The unnecessary replacement of satisfactory walls, often by concrete structures, results in high costs associated with construction, traffic disruption, increased risk of damage to property or life, and potentially adverse environmental impacts. The current lack of understanding of the real mechanisms of dry-stone retaining wall behaviour is perhaps unsurprising given that no significant experimental investigation of dry-stone retaining walls has been carried out since a limited study undertaken over 170 years ago. The resulting lack of direct quantitative data concerning dry-stone retaining wall behaviour is not only a problem in its own right, but has also hampered validation of modern computer-based numerical analyses.Increased use of dry-stone walling for repairs and new construction, and prolonging the service life of the existing stock, can only happen with a proper, validated, theoretically based understanding of how these structures work, and the development of suitable design methods that are applicable in the modern engineering environment. The two main areas of uncertainty currently hindering the efficient and accurate assessment of dry-stone retaining walls are bulging and wall thickness. The objective of the proposed research is to develop a greater understanding of these two key issues by means of an experimental study combined with parametric three-dimensional discrete element analyses, and the further development of limit equilibrium analysis methods for the design and analysis of existing dry-stone retaining walls.