CAJ | 학술논문

为探讨黄土高原主要造林树种刺槐和侧柏根系对土质边坡稳定性的作用，该文以刺槐（ Robinia pseudoacacia）和侧柏（Platycladus orientalis）为例，应用有限元数值模拟法构建二维造林边坡稳定性分析模型，研究林木根系的空间异质性对水平阶整地坡和对照自然坡稳定性的影响。研究发现：1）无论是否经过整地处理，造林都可以提高边坡的稳定性，且刺槐根系的固土效果优于侧柏根系（P<0.001）；2）在不考虑水文过程的前提下，水平阶整地模式的人工林边坡稳定性优于对照自然坡；3）当根系表观附加黏聚力增加到某一阈值后，造林边坡的安全系数进入平稳阶段不再大幅上升，说明边坡稳定性模型对根系附加黏聚力计算法的精度并不敏感，揭示了根系固坡领域的研究重点应从过去的试图提高根系附加黏聚力的计算精度转变为提高评价造林边坡稳定性的准确性；4）根系附加黏聚力随坡位的变化而变化，两树种没有明显的规律，但安全系数均表现出较敏感于坡下位根系，建议在林分经营管理中充分利用坡下位林木的固土效益。该研究成果可为黄土高原地区浅表层滑坡灾害的防治工作提供理论依据。
위탐토황토고원주요조림수충자괴화측백근계대토질변파은정성적작용，해문이자괴（ Robinia pseudoacacia）화측백（Platycladus orientalis）위례，응용유한원수치모의법구건이유조림변파은정성분석모형，연구림목근계적공간이질성대수평계정지파화대조자연파은정성적영향。연구발현：1）무론시부경과정지처리，조림도가이제고변파적은정성，차자괴근계적고토효과우우측백근계（P<0.001）；2）재불고필수문과정적전제하，수평계정지모식적인공림변파은정성우우대조자연파；3）당근계표관부가점취력증가도모일역치후，조림변파적안전계수진입평은계단불재대폭상승，설명변파은정성모형대근계부가점취력계산법적정도병불민감，게시료근계고파영역적연구중점응종과거적시도제고근계부가점취력적계산정도전변위제고평개조림변파은정성적준학성；4）근계부가점취력수파위적변화이변화，량수충몰유명현적규률，단안전계수균표현출교민감우파하위근계，건의재림분경영관리중충분이용파하위림목적고토효익。해연구성과가위황토고원지구천표층활파재해적방치공작제공이론의거。
To investigate the effects of major forestry species roots on slope stability on Loess Plateau of China, we used monospecific stands of Robinia pseudoacacia and Platycladus orientalis as a case study. Tree roots provide positive mechanical influence (i.e. additional cohesion) on slope stability. We used two different methods to determine root additional cohesion in this research, i.e. Wu and Waldron’s Model (WM) and revised WM (RWM). WM was developed based on limit equilibrium theory and assumed that all root in soil clods were mobilized in tension and fail simultaneously. Although WM approach was considered as a powerful and widely used method, it overestimated root additional cohesion due to all roots breakage simultaneously hypothesis. Therefore, based on many shear tests, a reduction factor for WM is introduced, which is RWM. The most critical parameters for WM and RWM were root area ratio (RAR) and root tensile strength. In this research, RAR was recorded on the soil trench profile, while root tensile strength was obtained by individual root tensile test. To evaluate tree roots effects on slope stability, a 2-D finite element model with terraced and contrast rectilinear surface shape of slope stability was developed and used to calculate the increase in factor of safety (FoS) due to root additional cohesion. Results showed that whether the land was prepared or not, afforestation can significantly increase slope stability. Moreover Robinia pseudoacacia roots were better that Platycladus orientalis roots on soil reinforcement. Terraced slopes were more stable than rectilinear slopes, regardless of the differences in hydrological regimes between these two terrain morphologies. It was also found that the percentage of FoS increase was larger when considering root additional cohesion simulated by RWM and virtual bare slope than root additional cohesion simulated by WM and RWM for both stands. Numerical sensitivity analyses for root additional cohesion illustrated that the relationship between FoS and additional cohesion was not linear, but exhibited as an asymptotic behavior. In detail, FoS value was stable when root additional cohesion reached the threshold value, which indicated that FoS was not sensitive to root additional cohesion calculation method. In addition, although root additional cohesion varied with the slope location, it was hard to find clear pattern to follow in our stands. However, roots in bottom part of slope always had stronger mechanical effects on slope stability. Therefore, more attention should be paid on the toe of slope and fully exerted its positive role for afforestation managers. This research can provide a basic theory of afforestation mode in spatial distribution and hence control shallow landslide.