含植被坡体稳定性的年际变化规律研究

植被对边坡稳定的影响主要体现在2方面,一是植物地上部分的自重以及风荷载对坡面的压力;二是植物根系的固土作用.植物种类和生长期对含植被坡体土壤抗剪强度的影响随植物的生长发育过程而变化,且这种变化难以量化.本文通过构建单株植物模型,分析含有不同类型植被的浅层均质土坡安全系数的年际变化规律.结果表明,在综合考虑植被自重、风荷载和根系的影响条件下,含侧柏和荆条的坡体安全系数会随着植物的生长发育逐渐增大,分别在树龄为50年和30年左右达到峰值1.549和1.817,随后趋于稳定,二者的峰值安全系数较植被种植初期分别增加46.8％和54.9％.植被自重和风荷载减弱坡体的稳定性,其中植被自重影响相对较小,使含侧柏和荆条坡体的安全系数分别降低0.1％和0.7％,而风荷载的影响较为明显,使其安全系数分别降低5.9％和5.8％.研究结果可为正确评估坡体稳定性以及布设植物护坡措施提供一定的科学参考.

On the inter-annual variability of vegetated slope stability

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.