【作者】 曹小红；

【导师】 言志信；

【作者基本信息】 兰州大学 ， 地质工程， 2012， 硕士

【摘要】 公路边坡植物防护技术是随公路建设而兴起的一门边坡防护技术,其与传统工程防护措施不同,利用植物根系固土护坡及生态、环保的特点,达到工程建设与环境保护、生态恢复兼顾的目的。不仅护坡植物根系具有粘结、摩擦、加筋、锚固等力学作用,而且护坡植物的水文效应通过茎、叶、枝条的截流、蒸腾、渗透作用能提高土体强度,控制地表水流,抑制坡面冲刷、侵蚀、溅蚀,降低坡体孔隙水压力。本文的主要研究工作是基于广泛的资料调研和野外调查,总结研究区地质概况,采样并进行室内试验：由室内试验获取土体基本物理力学参数；分析护坡植物的水文效应、蒸腾排水作用及力学作用,参阅前人的研究成果确定土体及护坡植物根的力学参数；建立边坡简化地质模型,通过设置一系列工况,采用FLAC2D软件Cable单元,模拟坡面植入不同入土长度、不同入土方向的单根及组合根,计算有、无植被作用下,边坡的塑性状态、应力、应变、位移及其变化,进而对比分析无植被、坡面植入单根、坡面植入组合根条件下护坡植物根的力学效应及其对边坡稳定性的贡献。经数值计算得出有植被边坡应力场重分布,剪应力分布有集中现象,并向坡底扩散和转移；X向位移最大值出现在坡脚稍向上部位,X向位移最大处剪应变率亦最大；边坡下部以剪切屈服为主,上部主要表现为拉张屈服；最利于边坡稳定的根植入方向为与水平面锐夹角成55.50方向,组合根侧根植入方向为30°优于18.5°、55.5°优于60°,最利于边坡稳定的组合根方式为主根垂直坡面方向、侧根与水平面成30°、55.5°方向植入；组合根作用下边坡X向位移减小,植入侧根部位剪应力向坡底扩散和转移、最大剪应变率出现在边坡上部根末端,且范围减小；根系固土护坡的力学作用体现在浅细根的加筋作用和深粗根的锚固作用使土体中的剪应力转换成根的拉应力,减小边坡X向位移,降低剪切屈服范围,提高边坡稳定性。更多还原

【Abstract】 As highway construction keeps growing in China, the slope protecting plants technology develops accordingly. This technology is also different from engineering protection measures in that it, characterized by environment-friendliness, makes use of plant roots to strengthen side slope. By so doing, the environment is preserved while the highway construction keeps carrying on.’The stems, leaves and branches of slope-protection plantation can intercept water flow, transpirate, osmose. Those functions are called hydrological effect, through which the soil can be consolidated, surface radial flow can be controlled, slope surface scour, erosion, splash erosion can be inhibited and the pore water pressure of slope can be lowered. The roots slope protection by vegetation is featured by mechanical effects, such as cohesion, friction, reinforcement, anchoring, etc.The main research method of this research includes information research, field investigation and the summary of the geology of the study area;testing the samples taken from study area in the laboratory;obtaining the basic physical parameters of soil and analyzing the hydrological effects、transpiration drainage effect and mechanics of the slope protection by vegetation; consulting the results of previous researcher to determine the mechanical parameters of soil and slope-protection plantation; establishing simplified slope geological model;through setting up a series of working conditions in FLAC2D software Cable element, simulating different implantation length and different implantation direction of the root upon slope;computing the slope’s plastic state, stress, shear strain, displacement on the condition of vegetation upon it and without vegetation upon it;then comparing and analyzing the mechanical effect of plant roots and their contribution to slope stability on conditions of implanted single root and implanted combined root upon it.Through the numerical calculation, vegetation slope stress field redistribution exists. And the phenomenon of shear stress distribution concentration exists as well,diffusing and transferring to the bottom of slope. The maximum value of X-displacement appears near the foot of the slope. Accordingly, the shear strain rate at the maximum X-displacement is at maximum, with the lower slope being at shear yield stress and the upper being at tension yield. The most ideal implantation direction is at a55.5°acute angle with the horizontal direction, an ideal direction for slope stability. The direction of combined root implanted is at an angle of30°, overmatching an angle of18.5°; the direction of lateral root implanted is at an angle of55.5°,overmatch an angle of60°.The pattern of assemble root which is most beneficial to the slope stability is that the main root stand vertical to the slope. The direction of root implanted is at an angle of30°and55.5°. Under the influence of assemble root, X-displacement decreases, shear stress in the lateral roots implanted diffuses and transfers to bottom of slopes and the maximum shear strain rate appears near the end of the root on the upper part of slope and its range has reduced. The mechanical effect of the root is reflected in reinforcement effect of the shallow and fine roots and the anchoring role of the deep and rough root, so that the shear stress in the soil is converted into the tensile stress of the root, e the X-displacement of slope is reduced, the range of shear yield is reduced and the slope stability is strengthened.更多还原