Biopolymer treatment for stabilisation of transport infrastructure slopes

斜坡崩塌(山泥倾泻)对我们的交通网络造成严重破坏。2015年，仅在铁路网上就记录了143起这样的故障。除了造成令人沮丧的延误外，这些故障还需要花费大量的维修费用。由于高降雨量，故障通常发生在冬季的几个月，但这只是一个可能已经发生了几年的过程的终点。长期暴露在英国不断变化的天气中会导致压实的粘土土壤，这些土壤形成了我们的高速公路和铁路所在的堤坝，随着时间的推移，它会变得越来越弱。当土壤反复被干燥，然后被干燥和潮湿的天气重新湿润时，就会产生非常细小的裂缝。这会影响水在土壤中的流动方式，裂缝使水很快进入斜坡深处，并可能形成巨大的压力，将土壤颗粒推开。通常，在炎热干燥的天气里会发生相反的情况。水分通过植物的蒸发和蒸腾作用从土壤中带走，这就产生了负压，迫使土壤颗粒聚集在一起，加固了坡度。这些负面压力在夏季积累起来，有助于在冬季保持斜坡的稳定。土体产生这些负压的能力因裂缝的形成而降低。这些因素的组合会使土壤变弱，以至于一次大降雨事件就可能导致斜坡不稳定。该项目将开发一种加固土坡并防止此类破坏发生的新方法。生物聚合物是由微生物作用形成的自然形成的聚合物，可以添加到土壤中以提高其强度并减少开裂的可能性。生物聚合物与土壤中的水混合形成凝胶，与土壤颗粒结合，使土壤具有更大的强度并降低渗透性。生物聚合物已经在化妆品和食品中用作增稠剂，因此它们相对便宜。它们也不需要大量的能源来生产，因此它们不像其他潜在的土壤粘结剂(例如水泥和石灰)那样与高二氧化碳排放有关。尽管生物聚合物的潜力以前已经被发现，但它们还没有被应用于斜坡稳定性问题，它们形成粘结和填充土壤孔隙的方式也没有得到充分的研究。该项目将对生物聚合物如何与压实土壤相互作用进行详细调查，并利用收集的信息开发一种新的粘结剂，适用于公路和铁路路基的维修和维护。

Slope failures (landslides) cause significant disruption to our transport network. In 2015 143 failures like these were recorded on the rail network alone. In addition to causing frustrating delays these failures also cost a significant amount to repair. Failures usually occur during winter months as a result of high rainfall but this is just the end point of a process which may have been occurring for several years. Long exposure to the UK's changing weather causes the compacted clay soil which forms the embankments that our highways and railways are built upon to weaken over time. Very fine cracks develop as the soil is repeatedly dried out and then re-wetted by periods of dry and then wet weather. This effects the way water moves through the soil, the cracks allow water to get deep into the slope very quickly and large pressures can build up, pushing soil particles apart. Ordinarily, during hot dry weather the opposite happens. Water is taken out of the soil by the action of evaporation and transpiration of plants, this induces negative pressures which force soil particles together, strengthening the slope. These negative pressures build up during the summer and help keep the slopes stable during the winter. The capability of soils to generate these negative pressures is reduced by the formation of cracks. A combination of these factors can weaken the soil to such a point where one large rainfall event can cause a slope to de-stabilise. This project will develop a new way of strengthening soil slopes and preventing these types of failure from occurring. Biopolymers, naturally occurring polymers formed by the action of microorganisms, can be added to soil to improve its strength and reduce the potential for cracking. The biopolymers mix with water in the soil to form gels which bind with soil particles giving the soil greater strength and reducing permeability. Biopolymers are already utilised in cosmetics and food as thickening agents so they are relatively cheap. They also do not require significant amounts of energy to produce and therefore they are not associated with high carbon dioxide emissions like other potential soil binders (e.g. cement and lime). Whilst the potential of biopolymers has previously been identified they have not been applied to slope stability problems and the way they form bonds and fill soil pores has not been studied fully. This project will carry out a detailed investigation of how biopolymers interact with compacted soils and use the information gathered to develop a new binder suitable for use in the repair and maintenance of highway and railway embankments.