采用有限差分软件FLAC3D对黄土高原坡沟系统及植被覆盖下重力侵蚀机理进行探索,对有无植被的坡沟系统应力场、 位移场和塑性区分布进行数值模拟,阐明了植被根系措施减缓重力侵蚀作用机制。结果表明,坡沟系统上部位移以"沉降"模式为主,下部位移以"剪切"模式为主,沟头溯源区是坡沟系统重力侵蚀最为强烈的部位;剪切塑性区域主要分布于坡面和沟坡大部分区域,张拉塑性区域主要分布于梁峁顶和梁峁坡上部;有植被覆盖时,根系加固作用改善了坡面浅层土体应力,有效降低了坡面土体的应力集中;减小了坡沟系统坡面浅层土体位移,使水平位移减少15%,铅垂位移减少2.5%;并减少了塑性屈服区体积,使剪切塑性区减少11.48%,张拉塑性区减少83.99%;减轻了重力侵蚀的破坏程度,但并未改变坡沟系统以剪切破坏为主的屈服模式。该研究为更好理解植被根系调控重力侵蚀研究提供了新的技术方法。
Mechanism of gravitational erosion in the slope-gully system and the root reinforcement reduction mechanism of the Loess Plateau was explored with the aid of the finite difference software, Flac3D, while numerical simulation of stress field and displacement field and plastic yielded zone with and without vegetation, and the reduction mechanism of root reinforcement was clarified. Results show that the displacement in the upper part of the slope-gully system appears mainly in the form of "settlement", and the displacement in the lower part appears mainly in the form of "shear", gully head traceability areas are most susceptible to gravitational erosion. The shear plastic zone is mainly distributed in most area of slope and gully slope, and the tension plastic zone is mainly distributed in tops and slopes of barren hills. As vegetation roots system reinforcement, the soil body stress of slope surface was improved, the extent of stress concentration and surface displacement were reduced effectively. The horizontal displacement and vertical displacement were reduced by 15% and 2.5% respectively. The volume of plastic yielded zone was also reduced, the volume of shear plastic zone and tension plastic zone were reduced by 11.48% and 83.99% respectively. The degree of damage of gravitational erosion was mitigated. However, the main failure model in the slope-gully system is still shear failure model. This study will provide a new method for understanding of vegetation root regulation on gravitational erosion.
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