On the inter-annual variability of vegetated slope stability
DING Xuekun, ZHANG Shouhong, WANG Yujie, WANG Yunqi, LI Yunpeng
1. School of Soil and Water Conservation in Beijing Forestry University, 100083, Beijing, China; 2. Beijing Engineering Research Center of Soil and Water Conservation, 100083, Beijing, China
Abstract：[Background] Effects of vegetation on slope stability are mainly embodied in two ways: a) the stress of weight and wind load caused by plants; b) the effects of plant roots reinforcement. The effects of plant species and growth stages on soil may change with time, which are difficult to measure and quantify due to existing technology. This paper aims to build a evaluation model that considers the plant growth and evaluates the safety factors of the slope under different layouts with different types of plants. [Methods] A growth model of individual-plant was used to obtain the inter-annual variation characteristics of plants. Meanwhile, height, DBH, canopy and number of root properties such as root quantity, branching patterns, and root inclinations were measured and discussed. Weight, wind load, and root reinforcement were also calculated in this paper. Finally, a modified equation was used to calculate the factors of safety of different vegetated slopes. [Results] Results showed that weight, wind load, and plants roots resulted in large impacts on slope stability. Slopes with Platycladus orientalis (L.) Franco, Vitex negundo var. heterophylla might enhance 46.8% and 54.9% compared to bare slope, reaching to the top 1.549 and 1.817 from the 30th year to 50th year respectively. After that, the safety factors of vegetated slopes tended to stabilize during the later growth. The effect of weight and wind load weakened slope stability. The influence of weight decreased safety factors about 0.1% and 0.7%, and the roots had decreased safety factors about 5.9% and 5.8%. [Conclusions] Based on the results, this paper concludes that the weight of plants and wind load may reduce safety factors, but root presents positive effect on slope stability. With the changes of years, effects of plant weight on slope stability mainly remain unchanged in the whole growth period. However, effects of root and wind load may increase during the early growth stage and then remain unchanged during the later stage. When evaluating vegetated slope stability, effects of plant weight, roots and wind load cannot be ignored or the safety factor may be overestimated or underestimated. In addition, the results provide reference to a reasonable layout in protecting slope and may be conducive to the ecological engineering construction.
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2017, Vol. 15 
