| Summary: | 碩士 === 中興大學 === 水土保持學系所 === 99 === In this study, the predominant plant species, Trema orientalis (L.) Blume, India charcoal trema commonly used in the vegetation engineering of slope in Taiwan was selected as a target plant for field investigations of root morphology, laboratory test of tensile strength of single root and in-situ vertical pull-out test of soil-root system. According to the root morphology and the strength parameters of root material, one can establish a three-dimensional (3-D) numerical model of soil-root system to simulate the pull-out behaviors of in-situ vertical pull-out test.
Subsequently, the simulation curves of vertical pull-out resistance Pv versus pull-out displacement Lp (or Pv~Lp curves) and the vertical ultimate pull-out resistance Pu of soil-root system were compared with those from the in-situ observations to verify the effectiveness of the proposed 3-D numerical model, simulation procedures, and material model parameters of various types. Using the identical 3-D numerical model of soil-root system, one can perform a numerical simulation of winch test (or lateral pull-out test) to model the mechanical behaviors of soil-root system as the trunk of India charcoal trema subjected to the wind loading. Similarly, from the simulation of winch test, one can obtain the lateral pull-out resistance versus pull-out displacement curves (or Pw~Lp curves) and the corresponding lateral ultimate pull-out resistance Puw.
Using the numerical results of vertical ultimate pull-out resistance Puv, lateral ultimate pull-out resistance Puw and the basal diameter of tree trunk D, one can establish three sets of conversion equation as: (1)Puv=f(D), (2)Puw=f(D) and (3)Puw=f(Puv, D) to correlate the lateral ultimate pull-out resistance Puw with the vertical ultimate pull-out resistance Puv of soil-root system.
Finally, a series of stability analyses of vegetated slope with or without subjecting to wind loading were performed using finite element c-phi strength reduction method. In which, the factor safety of vegetated slope is higher than that of bared slope about 2.08%~7.14% and 1.02%~7.03% respectively for the slope without and with subjecting to wind loading. In addition, the factor safety of vegetated slope decreases about 0.13%~1.06% when the slope is subjected to wind loading.
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