| This paper study on the form distribution of Larix gmelini root system at the Greater Higgnan Mountains.Then the PROE software was used to simulate the Larix gmelini root structure and adopt the axial uniform tensile stress to analyze the tensile mechanical characteristic of Larix gmelini.The purpose was to reveal the effects of root diameter,root length and stretching rate on the tensile strength of Larix gmelini root.The triaxial compression was used to evaluate the effects of root different disposition on soil shear strength. The comprehensive analysis of Larix gmelini root structure and the mechanical properties of soil were to provide theoretical data for Larix gmelini soil reinforcement.The results are as follows:(1)The total number and total length of root(diameter>1cm)in different ages of Larix gmelini was positively associated with age,the more stand age is,the more complex topological structure is. The survey on Larix gmelini root morphology found that there are minimum number of primary root and secondary root.an average of0.56,then the heart root and droop root, the number of oblique root and horizontal root is largest and with big variation, Standard wood which horizontal root is greater than7accounted for85.71%of the total sample number.(2)Oblique root branch diameter of Larix gmelini root is smaller than the horizontal root’s. There is a power function correlation between branch diameter of oblique root and horizontal root and DBH. Oblique root and horizontal root diameters were decreased with the increase of root length.it presents the logarithmic function negative correlation.Larix gmelini different diameter root length percentage and specific root length were decreased with the increase of root diameter.Specific root length,specific root length in different plot was negatively correlated with stand age.The young forest contains more fine roots than middle age forest and near mature forest, as well as root volume ratio and age were positively related,the two was the opposite trend.the greater the specific root length,the smaller the root volume ratio. (3)Larix gmelini individual plant root biomass and root mass density were increased with the increase of stand age.The individual plant biomass in Ledum palustre-Larix gmelinii near mature forest is biggest,with48.87Kg/strains,while the root mass density is least,with29.23×10-5g/cm.The order of the total dry matter of Larix gmelini different diameter root is as follows,2-5cm,5-10cm,>10cm,1-2cm.<lcm.The diameter class of2-5cm dry matter is33.58Kg.Individual plant root biomass of Larix gmelini and DBH as well as age present positive exponential function, it presents positive power function with root length.(4) The7strains of standard root as the soil becomes deep,the total root length decreases, the root content in0-20cm soil layer is the largest, and more for horizontal root,20-40cm, is more inclined to take root,40-60cm soil layer contains only a few of the vertical root, and only plantation and Ledum palustre-Larix gmelini nearly mature forest root system distribution in40-60cm soil layer; Root length density, dry matter in different forest types and root volume ratio increases with the degree of soil all showed a trend of decrease after the first increase, and both maximum between0-20cm soil layer; Different forest types Larix gmelinii tree root vertical distribution model of the horizontal root system to weaken the coefficients are concentrated in between0.86-0.93, lower than the global average, for the typical level type root tree species, the overall level of the competition and CI index is higher, shows that Larix gmelinii tree level root growth competition capacity is larger.(5) by using Pro/Engineer5.0well established Larix gmelinii root system, a three-dimensional simulation model into ANSYS11.0analysis Larix gmelinii root out strength under the condition of stress distribution.(6)Larix gmelinii root tensile strength and the diameter was significantly negative relationship, and meet the power function, and negatively related gage and stretching rate overall, and as the range and the increase of stretching rate, the range of tensile strength are reduced; Larix gmelinii root stress-strain curve of maximum tensile strength, elastic modulus and elongation were decreased with the increase of diameter and the distance, has significant negative correlation relationship, and stretching rate showed a trend of first decreases increased:Larix gmelinii root cyclic tensile fatigue can increase the maximum tensile resistance and tensile strength of root system, and circulation, the more the greater the impact on the tensile strength of root system, and with the increase of root system fatigue cycles, fatigue hysteresis ring area is reduced accordingly, curve slope difference decreases at the same lime. (7) utilize modern complex of larch root soil cohesion and internal friction Angle (Φ)(C) were greater than the soil, buried and mixed root complex is better than vertical and horizontal buried buried root root, root way, same as the increase of the buried root segment diameter, the cohesion (C) and Angle of internal friction (Φ) increased gradually, positively correlated relationship. |
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