摘要
植物是天然的工程师,拥有防止浅层滑坡和地表侵蚀的潜能,并具备低投入、易养护、绿色环保和生态平衡等优点。目前国内外的研究和工程实践大多只考虑植物根系的力学加筋作用,而忽略了更为重要的水力作用。植物蒸腾能增加土体吸力,从而降低土体渗透系数且增加抗剪强度,所以能提高边坡稳定性和防止地表侵蚀。笔者的跨学科研究团队结合高等非饱和土力学理论和植物特征,从根本上研究了大气–植被–土体的相互作用机理;提出了新的理论模型,可预测植被土的持水能力;构建了考虑植物根系形状影响的地下水渗流与地表径流耦合运移的新模型;推导了计算植被边坡吸力分布与稳定性安全系数的解析解,引入了指数形、三角形、均布形和椭圆形4种典型的根系形状;并自主研发了用于离心机模型试验的人造根,能够模拟不同形状的植物根系的水力作用和力学加筋作用,并利用其揭示了根系形状对边坡的变形与破坏机理的影响。为保证研究的基础性和实用性,选取了百慕大草和鸭脚木树两种代表性植物,并考虑了种植间距与真菌等因素的影响。主要研究结果揭示:(1)植物在干燥与降雨条件下均能明显提高土体吸力,提高边坡稳定性;(2)植物引起的土体吸力可以用叶片面积指数和根表面积系数等植物特征参数量化,并且鸭脚木树的叶片面积指数和根表面积系数之间存在着线性关系;(3)真菌能显著提高植物根系的抗拉强度,加强植物的力学加筋作用;(4)所研究的4种根系形状中,指数形根最有利于提高边坡稳定性。上述研究包括室内试验、现场监测、离心机试验和理论建模等方面,建立了一套科学合理的理论框架与测试方法,并为植物护坡的工程实践和"海绵城市"的建设提供科学依据。
Plants are sophisticated and intelligent natural construction materials. They can be used for enhancing the stability of shallow soil slopes and minimizing surface erosion. It is evident that the use of plants can be low-cost, sustainable （almost maintenance free） and environmentally friendly. Not only can plant roots provide mechanical reinforcement, they can also induce soil suction via evapotranspiration （hydrological effects） to increase soil shear strength and to reduce water permeability for minimizing rainfall infiltration in the ground. Most previous researches have mainly focused on the mechanical effects of roots, while the mechanisms and contributions of induced soil suction to slope stability are often ignored. A multi-disciplinary research team led by the author has carried out an in-depth study on the mechanisms of atmosphere-plant-soil interactions based on the advanced theories of unsaturated soils and plant characteristics. New constitutive models are developed to estimate the water retention ability of vegetated soils and to simulate conjunctive surface and subsurface transient flow considering different root architectures. In addition, a new analytical model is derived to calculate soil suction induced by roots having one of four architectures （i.e., exponential, triangular, uniform and parabolic distributions with depth） and thereby to predict the factor of safety of vegetated soil slopes： Moreover, a novel artificial model root system is developed to simulate both mechanical and hydrological effects of roots in centrifuge. The influences of root architectures on induced suction, slope stability and deformation mechanisms are investigated. The experimental and theoretical results reveal that （1） vegetated soil is able to retain higher suction than bare soil under both drying and wetting conditions; （2） for Schefflera heptaphylla （Ivy tree）, a commonly found plant species in many Asian countries, there is a linear relationship between root area index and leaf area index, which in turn has an approximately linear relationship with evapotranspiration-induced soil suction; （3） fungi can significantly increase root tensile strength and therefore enhance the mechanical reinforcement effects of roots; （4） among the four types of roots investigated, the exponential one induces the highest suction and hence is the most effective in stabilizing shallow soil slopes. Through extensive laboratory testing field monitoring, centrifuge modelling and theoretical analysis, this study has established a theoretical framework, developed a novel testing technique in centrifuge and contributed towards the fundamental understanding of atmosphere-plant-soil interactions. The findings from this study also provide a scientific basis for the design of vegetated soil slopes.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2017年第1期1-47,共47页
Chinese Journal of Geotechnical Engineering
基金
香港特别行政区研究资助局协作研究金项目(HKUST9/CRF/09和HKUST6/CRF/12R)
国家重点基础研究发展计划("973"计划)项目(2012CB719805)
