公路边坡植物的护坡机理

从植物根系的力学作用、植物的蒸腾排水效应、茎叶及枯枝落叶的水文效应3个方面,分析了公路边坡植物的护坡机理。通过对植物根系的力学作用分析,建立了草本植物根系的加筋力学模型及木本深根植物的锚固力学模型。三轴剪切试验结果表明,沙棘、沙柳须根的加筋作用使沙土的粘聚力c值提高了2.5~4.0倍,使粘性土的粘聚力c值及内摩擦角φ值均增加0.25~0.40倍。应用非饱和土理论,定量分析了植物蒸腾排水效应对边坡的稳定贡献,现场监测试验表明,即使在雨季,柳树植物根系范围内土中的孔隙水压力仍为负值。依据植物边坡稳固机理,将植物护坡总结为坡面冲刷防护与边坡加固两种设计类型。坡面冲刷防护可根据浅根表土加筋与茎叶水文效应机理进行设计;边坡加固可根据深根锚固作用与蒸腾排水效应机理设计。

Mechanism of biotechnichal protection for highway slope

The mechanism of biotechnical slope protection was studied from three aspect of roots mechanical function, hydrologic effect of stem and leaf (includes dead branches and fallen leaves), and transpiration effect of plant. To the roots mechanical function, 2 calculation formula models, the shearing strength and anti-splitting strength model,were developed in the condition of surface soil reinforced with herb-root and slope anchored with taproot model. The triaxial shearing test showed that the cohesion of sand reinforced with the fibre of sand thorn or sand willow was increased by 2.5~4 times; the cohesion and the angle of internal friction were increased by 0.25~0.40 times for the reinforced clay soil. The contribution of plant transpiration effect to slope stabilization were analyzed quantitativly. The latest field trial data, which was collected from international, showed that the soil pore pressure commonly was negative in the scope where willow roots extended. In terms of mechanism of function, the biotechnical slope protection design was divided into 2 types: the slope erosion controlling and the slope stabilization. The slope erosion controlling design can be based on the function of the surface soil reinforced with herb-root and the hydrologic effect of stems and leaves; the slope stabilization design can be based on the function of the slope anchored with taproot and the plant transpiration effect. 2 tabs, 3 figs, 10 refs.