Hydro-mechanical properties of lime-stabilised shrinkable UK clays

一些高塑性粘性土在干湿季节循环中表现出较大的体积变化。这种粘土被称为可收缩粘土或膨胀粘土。在英国，可以在英格兰南部和东部找到一系列可收缩的粘土。由于它们的存在，水分含量的季节性变化可以导致每年高达50毫米的地表移动。这可能会对土木工程结构(特别是轻型建筑物和人行道)造成严重的破坏和破坏。此前的研究估计，收缩土壤造成的破坏可能高于任何其他自然灾害造成的破坏，包括地震和洪水。这可能导致每年数百万英镑的房屋损失，因为数百万户家庭受到影响，还导致英国低层建筑(主要是住房)沉陷损害的保险索赔迅速增加。受影响的基础设施(路面、铁轨等)的保养和维修费用也可能非常高，可能会造成严重的交通延误。改善收缩土的工程性质和防止结构损坏的其中一种方法是使用化学添加剂，特别是石灰来稳定土壤。这项技术特别有吸引力，因为它允许就地改良和使用土壤。因此，与传统方法相比，这往往是一个更经济(在时间和金钱上)和更环保的替代方法，即将不适合的土壤移至堆填区并将其处置，并用进口的采石碎石材料取代。当石灰处理材料就位时，它会受到环境影响，包括湿润和干燥的季节性循环。这意味着在其设计寿命内，石灰处理的土壤将处于不同的状态，从完全饱和的水到几乎完全干燥。当土壤处于部分饱和状态时，其行为和性质与完全饱和时完全不同。因此，重要的是要了解它在这两个州的属性和行为。随着这项技术在更广泛的项目和应用中的广泛使用，出现了对能够描述各种问题和条件(包括部分饱和土壤条件)的石灰处理土壤行为的预测性数值工具的需求。这种类型的土壤目前还没有这样的工具。这项研究的目的是开发能够进行预测的计算机软件。这将基于对石灰处理的英国粘土土壤的新的实验数据，这将允许为石灰处理土壤的行为创建一个合适的模型。这项研究的另一个新颖性是，完全饱和和部分饱和的土壤条件都将被考虑在内。预测工具将使工程师能够执行复杂的分析，并在各种应用中对石灰处理材料的行为做出更明智的决定。这项研究是及时的，因为随着气候变化导致的极端天气条件变得更加常见，预计由于土壤周期性收缩/膨胀而产生的工程问题在未来几年将会增加。此外，目前存在越来越大的环境和经济压力，要求通过稳定就地土壤来升级材料，作为将其出口到垃圾填埋场和用进口颗粒填充物取代的替代方案。特别是，欧盟关于垃圾填埋的指令(理事会指令1999/31/EC)也已移交给英国，该指令的基础是以更可持续的方式管理资源的政策目标。用石灰改良就地土壤是一种可持续的解决方案，因为它节省了施工时间和资金(包括垃圾填埋税)，并减少了车辆排放。

Some clay soils of high plasticity show large volumetric changes in response to seasonal cycles of wetting and drying. Such clays are called shrinkable or expansive clays. In the UK, a range of shrinkable clays can be found in South and East England. Due to their presence, seasonal variations in moisture content can cause annual surface movements as high as 50mm. This can cause significant distress and damage to civil engineering structures (in particular light buildings and pavements). Previous research has estimated that the damage caused by shrinkable soils may be higher than damage due to any other natural hazard, including earthquakes and floods. This can result in millions of pounds of damage to homes every year, as several millions of homes are affected, and has also led to a rapid increase in insurance claims for 'subsidence damage' to low-rise buildings, principally housing, in the UK. Maintenance and repair cost of the affected infrastructure (pavement, railway tracks etc) can also be very high and may incur severe traffic delays.One method to improve the engineering properties of the shrinkable soil and prevent damage to structures is to stabilise the soil using chemical additives and in particular lime. The technique is particularly attractive, as it allows the improvement and use of the soil in-situ. For this reason, it is often a more economic (in terms of both time and money) and environmentally-friendly alternative to the conventional methods, which involve removal and disposal of the unsuitable soil to landfills and its replacement with imported quarried aggregate material. When the lime-treated material is in place it is subject to environmental effects, including seasonal cycles of wetting and drying. This implies that during its design life, the lime-treated soil will be at different states, from being fully saturated with water, to almost completely dry. When the soil is in a partially saturated state, its behaviour and properties are fundamentally different from those when it is fully saturated. It is therefore important to know its properties and behaviour in both states. Such a complete picture of the lime-treated soils is currently lacking.With the scope of an increased use of the technique in a wider range of projects and applications, the need has emerged for predictive numerical tools able to describe the behaviour of lime-treated soils for a variety of problems and conditions (including partially saturated soil conditions). Such tools are not available at the moment for this type of soil. The aim of this research is to develop computer software which will allow predictions to be made. This will be based on new experimental data on lime-treated UK clay soils, which will allow to create an appropriate model for the behaviour of the lime-treated soil. An additional novelty of the research is that both fully saturated and partially saturated soil conditions will be considered. The predictive tool will enable engineers to perform sophisticated analyses and to make better informed decisions on the behaviour of lime-treated materials in a variety of applications. The research is timely as with extreme weather conditions becoming more common due to climate change, engineering problems due to cyclic shrinkage/expansion of soils are expected to rise in the years to come. Moreover there is currently an increased environmental and economic pressure to upgrade material by stabilisation of in situ soil, as an alternative to its export to landfill and replacement by imported granular fill. In particular, the EU Landfill Directive on the Landfilling of Waste (Council Directive 1999/31/EC) which has also been transposed to Britain, is based on the policy objective to manage resources in a more sustainable manner. Improving the in-situ soil with lime is a sustainable solution, as it saves construction time and money (including landfill taxes) and reduces emissions from vehicles.