Development of reinforcement work for forest revegetation on steep slopes

本研究旨在探讨林木根系对边坡稳定性之保护与强化作用，以发展适当之边坡防护工程。主要研究结果如下：1）根系分布的野外观测与模拟研究将根系分布对边坡稳定性的影响视为横向和纵向根系共同作用的结果。侧根像在土壤表面撒“网”一样保护土壤表面不受表面侵蚀。另一方面，垂直根系加强边坡稳定性，就像将“短锚”打入地面一样。树木根系分布与草本植物根系分布的不同之处在于树木根系向坡上部生长。2）树木根系对边坡稳定性作用的理论分析从理论上探讨了树木根系对边坡稳定性的加固作用，并与其他人工材料（如铁桩、管道、锚杆等）进行了比较，定量评价了树木根系对边坡稳定性的加固作用。树根是理想的增强材料形态。但也有一些限制。一是材料本身强度不足。此外，树根也不够强壮，无法渗透到坚实的土壤中。边坡稳定性随植物生长沿着逐渐降低。3）陡坡绿化加固工程的指导树木根系对边坡稳定性的影响是显而易见的，但也存在一定的局限性。建议采用天然树根与其他人工材料相结合的方法。本文提出的加固效果理论评价方法，对工程设计具有一定的参考价值。

This research addresses the role of forest roots for securing and reinforcing slope stability for the purpose of developing proper reinforcement work for revegetating forest on steep slopes. The results of this study are as follows ;1) Field observation and modeling of root distributionThe effects of root distribution for slope stability are considered as the combination of lateral and vertical roots. The lateral roots protect soil surface from surface erosion like casting "nets" over soil surface. On the other hand, vertical roots reinforce slope stability like driving "short anchors" into grounds. The difference of root distribution between trees and grasses is that tree root grow toward upper slope.2) Theoretical analysis on effects of tree roots for slope stabilityThe effects of tree roots for reinforcing slope stability are investigated theoretically and are evaluated quantitatively as compared with other artificial materials, like iron stakes, pipes and anchors. Tree roots have ideal morphology as reinforcing material. But there are some limitations. One is the shortage of strength as material itself. Also Tree roots are not strong enough to penetrate into firm soils. Slope stability decreases gradually along with plant growth.3) A guide of reinforcement work for revegetating forests on steep slopesIt is obvious that tree roots have significant effects on slope stability, but there are some limitations. The combination of natural tree roots and other artificial materials are strongly advised. The method presented in this study evaluating reinforcing effects theoretically should be useful for designing proper work.