【作者】 周朔；

【导师】 陈丽华；

【作者基本信息】 北京林业大学 ， 农业生物环境与能源工程， 2011， 硕士

【摘要】 森林生态系统中的根系不但可以吸收与传输溶质与水分,同时还有支撑树体与固结土体的重要作用,能够减缓浅层滑坡、崩塌等重力侵蚀。本论文选取华北地区北沟林场常见乔木：油松、白桦、落叶松、蒙古栎,进行拉伸试验,测定其拉伸力学特性,提供基础资料数据,旨在对林木根系的研究提供一些参考依据。通过试验结果表明：乔木根系抗拉强度与根系直径存在负相关,且成幂函数关系。根系最大抗拉力与直径间关系为正关系,且成幂函数关系。在相同直径条件下,标距较小的根系有较大的抗拉力和抗拉强度,在直径较小的情况下,各标距抗拉力和抗拉强度差异并不明显,但随直径的增加,差距增大。根系的应力应变曲线分析中,都是在直径较小的时候,随应变增加,应力呈线性增大,表现出较好的线弹性关系,直径增大后,应力应变曲线递增缓慢,没有明显的线性区间。随着直径的增加,根系抗拉强度、延伸率、弹性模量均相应降低,应力—应变曲线弹性表现不明显。随根系标距增大,根系抗拉强度、残余应变相应降低,弹性模量变大。以400mm/min和10mm/min不同速率拉伸根系,根系在400mm/min下大多为脆性断裂,易拉断破坏。相同根径时,拉伸速率越大,根系抗拉力、抗拉强度越小；根径越大,不同拉伸速率下根系抗拉力、抗拉强度的差异会变大。对根系进行轴向疲劳往复试验,疲劳后根系抗拉力及抗拉强度明显增高,随着循环次数的增加,相同直径的弹性模量呈递减趋势,每次循环产生的应变也相应减小。更多还原

【Abstract】 Roots in forest ecosystems not only absorb and transport solute and water, but also support the tree and consolidate soil. By selecting four common kinds of arbor root system, Pinus tabulaeformis, Betula platyphylla, Quercus mongolica and Larix gmelinii, the mechanical characteristics of root system are investigated by performing tensile experiments.The results show that the tensile strength of arbor roots has a negative correlation with root diameter and that they are in a power function relationship. The tensile resistance of the root system has a positive correlation with root diameter, and they also present a relationship of power function. The tensile resistance and tensile strength decreases with increasing gauge length of roots under the same diameter. Analysis of the stress-strain curves of the root system indicates that the strain increases linearly with increasing stress in the case of smaller diameter roots, and they have a good linear elastic relationship. However, the stress-strain curves increase slowly, with no apparent linear range, with increasing diameters. With increasing diameter, the tensile strength, critical strain and elastic modulus of the four kinds of arbor roots decreases accordingly.With increasing gauge length under the same diameter, the residual strain of root decreases and the elastic modulus of the root increases. The tensile resistance and tensile strength decrease with increasing rates of extension of roots under the same diameter. When the diameter is small, the gap of tensile strength between different rates of extension of the root is not obvious. However, the difference of the tensile resistance and tensile strength becomes increasingly bigger as the diameter increases. The root tensile strength increases after fatigue test. With increasing cycling times, the residual strain and elastic modulus of root decrease.更多还原