Study On Tensile Mechanical Characteristics Of Root System

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.