土体含水率与根系埋深对银杏树苗抗拉拔性能的影响

中国是受热带台风灾害影响最为严重的国家之一,由于强风暴雨作用引起的林木根系拔出及倾倒破坏致使交通中断、车辆受损、人员伤亡等次生灾害与日俱增。为进一步研究土体物理特性对林木抗拉拔性能的影响,采用自主设计的根系横向加载试验系统,通过对银杏树苗施加定速率横向加载的拉拔试验,模拟外力荷载下根系的倾倒过程。试验设置了5组梯度含水率和4种埋深工况分析土体含水率、根系埋深对拔出过程中抗拉拔力的影响。研究表明:在粉质砂土中,黏聚力根系位移抗拉拔力曲线中抗拉拔力的变化可以概括为平缓上升、陡峭上升和缓慢上升达到峰值3个阶段;最大抗拉拔力随含水率提升呈现先升后降的总体趋势,与土体黏聚力变化的总体趋势相同,当含水率趋近饱和含水率时,最大抗拉拔力衰减显著;当含水率一定时,根系的最大抗拉拔力随着根系埋深的增加,在试验设置的埋深区间内呈线性趋势增长。

Effects of soil moisture content and root depth on anti-overturning performance of Ginkgo biloba seedings

China is one of the countries most seriously affected by the tropical typhoon disasters. Root pull-out and toppling damage caused by severe storms and rains occur frequently. Secondary disasters such as traffic disruption, vehicle damage and casualties are increasing. In order to investigate the effect of soil physical properties on the anti-overturning performance of trees, the pulling test of Ginkgo biloba seedlings under constant lateral loading rate was carried out through a self-designed lateral root loading test system to simulate the dumping process of roots under external load. Five sets of gradient water content and four buried depths were set to analyze the influence of soil moisture content and the root depth on the pull-out resistance during the pull-out process. The research indicates that in silty sand, the change of the anti-overturning force in the root displacement-drawing force curve can be summarized as three stages:gentle rise, steep rise and slowly rising to reach the peak. The anti-overturning force with the increase of moisture content showed the first rise. The overall trend of the post-fall is the same as the overall trend of the change of soil cohesion. When the moisture content approximates the saturated moisture content, the maximum anti-overturning force is significantly reduced. When the moisture content is constant, the maximum anti-overturning force of the root system increases linearly with the depth of the root system in the buried depth range set by the test.