Role of geometric characteristics of plant roots in the mechanical mechanism of vegetated slopes

• Main Authors: Chung-hao Chen, 陳炯豪
• Other Authors: Chia-cheng Fan
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/16560177974369890775

碩士 === 國立高雄第一科技大學 === 營建工程研究所 === 104 === Ecological engineering is one of many methods designed to improve slope stability. Plant root systems are crucial to slope stability. However, various factors develop into different geometric conditions, causing plant root systems to grow in different ways and consequently affecting slope stability in many ways. Adopting various geometric conditions to examine root systems’ mechanics mechanism in relation to slope stability, this study established numerical slope using Plaxis3D and then simulated plant root systems using Embedded Pile so as to create a vertical taproot and two lateral roots with different slanting angles for research under different geometric conditions provided for plant root systems. Major research projects included: (1) the role played by the entire plant root system in slope stability under different geometric conditions, (2) discussion of the entire plant root system’s mechanics mechanism, (3) the roles played by different parts of plant in slope stability under different geometric conditions, and (4) discussion of different parts’ mechanics mechanism. 　　Upon completion of the numeric simulation for plant roots in slope, results were summarized as follows: (1) Plant root system’s geometric conditions affected slope stability tremendously. According to the research results, root system made a minimal contribution to slope stability when nothing else but Young’s modulus was increased. The contribution started to increase as soon as root diameter grew larger. The contribution grew the most when root diameter and Young’s modulus were increased simultaneously. (2) Plant root system’s axial pressure force was one of many important factors that affected slope stability; the larger the plant root system’s slope steady contribution, the larger the pressure force released by taproot. (3) The entire slope displacement was compared with the slope steady contributions made by root system. According to the comparison results, nothing else but the top of slope and the upper slope were displaced when plant root system had radiculose diameter because the slope had a uniformly distributed load on its top. As soon as root diameter grew larger, the root’s surrounding areas in mediolateral slope, in addition to the upper slope, were more or less displaced. When plant root system grew thick, the root’s surrounding areas in mediolateral slope and the lower part of slope, in addition to the upper slope, were obviously displaced. Apparently, the degree of displacement indicated how the root system’s geometric conditions affected the vegetated slope. (4) The slope steady contributions made by root systems in different positions are related to one another. When roots were flexible, the roots in upper taproot made more contribution to slope stability than the roots in lower taproot. As soon as Young’s modulus grew larger and root’s stiffness grew to a certain level, the roots in lower taproot contributed to slope stability more obviously than the roots in upper taproot. Moreover, geometric conditions varied, depending on how the large angle between slope and oblique roots as well as the small angle between slope and lateral roots developed. (5) The mechanics mechanism in each part of the plant was obtained by comparing taproot’s bending moment with its axial force. When axial force developed into tension, no bending moment was formed. As soon as axial force turned into pressure force, taproot’s bending moment started to develop. Moreover, bending moment’s development and plant roots’ slope steady contributions follow the same trend. Apparently, the larger the slope steady contributions, the more obvious the bending moment.