| Root is an important organ of vegetation to adapt long-term land conditions, which have the function of both anchor plant and absorption, synthesis, transport, metabolism. The root solid earth ability mainly affected by plant species, plant root morphology, the mechanical properties of plant roots and the interaction between plant roots and soil interface. Based on theories and methods in elasto-plasticity mechanics, soil mechanics, soil and water conservation, forest ecology and etc., the study has made both field and lab experiments, taking an example of Pinus tabulaeformis, based on root morphology and fractal characteristics, mechanical properties of a single root, and the interaction between plant roots and soil interface to study the influence factors of plant roots soil reinforcement mechanism.The main research results are as follows:(1) The investigation and analysis of Pinus tabulaeformis roots showed that, roots level have taproots and lateral structure, the overall structure of cones, lateral roots evenly distributed in all directions. Lateral root length and biomass are mainly distributed in the upper part of the main root, and increases with the increase of DBH and tree height. There is little difference of fractal dimension of root system, and the second level of lateral space occupied ability better than the first lateral roots level(2) The study of tensile tests of root system and soil characteristics showed that, Pinus tabulaeformis root tensile resistance, tensile strength and stress-strain relations are affected by the depth of the soil layer. Tensile resistance and tensile strength of root system have significantly correlated with most of the soil physical, chemical and biological properties. Gauge length and stretching rate have a significant effect on the tensile properties of root system. Pinus tabulaeformis roots tensile properties are significantly different in different slope and different growth directions. Diameter is the main factor affecting the tensile strength of root system. The impact of tensile resistance and tensile strength by gauge length is greater than the tensile rate in test control factors. The impact of tensile resistance by slope direction is greater than soil depth and direction of growth in environmental factors. The maximum influence factor of the tensile strength is slope direction, followed by the direction of root growth and soil depth.(3) Triaxial tests showed that the root soil composite ultimate principal stress difference increases with the increases root diameter and the confining pressure, and decreases with improved soil moisture. The test shows the result of the complex>vertical>horizontal roots in limit of principal stress difference. Large diameter and confining pressure, complex root distribution, making the greater shear strength.(4) With the root soil shear strength was significantly greater than the prime soil shear strength. Under certain soil conditions, the influencing factors of complex root soil shear strength is the same with the ultimate principal stress difference. Root diameter, confining pressure and roots buried approach is the main factors of soil shear strength of the soil-root composite.(5) Plant roots-soil interface friction increases with the root diameter increased in a linearly law. Depth, soil moisture and loading rate has a significant impact on the root-soil interface friction. Friction increases with depth increases linearly. Within a certain range, the average friction showing the first increase and then decrease with increasing soil moisture variation. The average friction linearly decreases with the increase of loading rate.(6) Plant root soil interface friction coefficient showing the first increase and then decrease with increasing diameter. Depth, soil moisture and loading rate has a significant impact on the root-soil interface friction coefficient, the changing law is similar to the law of friction. |
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