Bio-engineering Mitigation Debris of Flow

在气候变化的影响下，泥石流灾害日益增多，造成了严重的社会经济损失。现有的缓解方法包括混凝土挡板，但这些方法具有高的二氧化碳含量，这将进一步促进气候变化。坡面生物工程，如灌木层[1]是一种替代性的“绿色”低碳技术（图1）。植物枝条可用于衰减碎片冲击能量，随后可调动根部拔出阻力以抵抗在植物上诱导的拖曳力。然而，没有研究评估这种土壤-植物-泥石流相互作用及其对泥石流流动性的影响。这个博士项目的目的是调查使用刷分层，以减少流动性的泥石流质量的有效性。本项目的目标是：㈠确定碎片团运输过程中施加在植物枝条上的拖曳力; ㈡量化土壤-根系机械拔出抵抗拖曳力的阻力; ㈢量化由于生物工程减缓而减少的流动团流动性; ㈣评价灌木分层技术相对于刚性挡板方法的性能;将开发一个新的大型实验水槽，用于模拟不同的泥石流事件。刷层将通过3D打印一些代表性的植物性状来建模[2]，因此（i）无需等待植物生长，（ii）实现可重复的结果。已知体积的干颗粒土的泥石流事件将在水槽的上游触发。将监测穿过灌木层的碎片团的流动特性的任何变化，并与没有生物工程缓解措施的情况和通过刚性挡板缓解的情况进行比较。将鉴定可提高生物工程技术性能的任何有利的植物性状和植物布置。等，2015年。山坡不稳定性的生态减缓：研究者与实践者面临的十个关键问题。植物与土壤，377：1 - 23。等，2014年。从单个根土相互作用到整体边坡行为的有根边坡抗震性能建模，岩土工程，65（12）：995 - 1009。

Under the impact of climate change, rainfall-induced debris flow events have been increasingly reported and these have led to significant socio-economic losses. Existing mitigation methods include concrete baffles, but these methods have high embodied CO2 that would further promote climate change. Slope bioengineering such as brush layering [1] is an alternative, "green" and low-carbon technique (Fig. 1). Plant shoot might be used to attenuate the debris impact energy, and subsequently the root pull-out resistance may be mobilised to resist against the drag force induced on the plant. There is, however, no study evaluating such soil-plant-debris interaction and its effect on debris flow mobility. The aim of this PhD project is to investigate the effectiveness of using brush layering to reduce the mobility of a debris flow mass. The objectives of this project are to(i) Determine the drag force exerted on plant shoot during the transport of a debris mass;(ii) Quantify the soil-root mechanical pull-out resistance against the drag force;(iii) Quantify the reduced mobility of a flow mass due to bioengineering mitigation; and(iv) Evaluate the performance of brush layering technique against rigid baffles method;A new large-scale experimental flume will be developed for modelling different debris flow events. Brush layering will be modelled by 3-D printing some representative plant traits [2], hence (i) removing the need to wait for the plant growth and (ii) enabling repeatable results. Debris flow event with a known volume of dry granular soil will be triggered at the upstream of the flume. Any changes of the flow characteristics of a debris mass across the brush layering will be monitored and compared with cases without bioengineering mitigation, and cases that mitigated by rigid baffles. Any favourable plant traits and plant arrangement that could enhance the performance of the bioengineering technique will be identified.References:Stokes, A., et al. 2015. Ecological mitigation of hillslope instability: ten key issues facing researchers and practitioners. Plant and Soil, 377: 1 - 23.Liang, T., et al. 2014. Modelling the seismic performance of rooted slope from individual root-soil interaction to global slope behaviour, Geotechnique, 65(12): 995 - 1009.