| Summary: | 碩士 === 國立中興大學 === 水土保持學系所 === 94 === This study determines the three basic data, which are light-shielding rate, surface roughness (by Manning’s coefficient) and apparent opening size, of the nonwoven three-D netting, woven serfertnet method as well as three-D iron diamond compound netting of plastic materials by related experimental equipment; uses artificial rainfall instrument and hydraulic launders to conduct soil erosion and trap tests to get the different effects of different materials on soil erosion prevention and vegetation; and, tests and verifies the reliability and necessity of indoor tests by contrasting on-the-spot investigation data.
The test of artificial rainfall takes the agricultural soil that is with the thickness of 10cm and from Lugu Township of Nantou County at the altitude of 800m as the bottom soil. Artificial materials are laid on the surface, and then, the organic soil without any adhesive with the thickness of 3cm is sprayed on it. The testing conditions are the gradients of 15˚ and 45˚ and the rainfall intensity of 130mm/hr. Soil erosion tests are separately conducted for 20min on the three artificial covering materials and the laid control group. And, the trap efficiency of different materials are determined by adding homogenized sand grains with the fixed quantity into the steady launder with the gradient of 4.5˚. According to the test, the nonwoven three-D netting with the light-shielding rate of 63%, the Manning’s coefficient of 0.080 and the irregular structural type has the highest anti-erosion efficiency in the soil erosion test. The serfertnet method with the light-shielding rate of 66%, the Manning’s coefficient of 0.163 and the regular structural type has the best efficiency in the trap test. However, both the two efficiency of the three-D iron diamond compound netting with light-shielding rate of 27%, the Manning’s coefficient of 0.037 and regular structural type are low.
As to the differences between vegetation restoration effects, this study develops the mode illustration of vegetation restoration hydrograph with the three modes of normality, slowness and fault by adopting the graph of plant growth (Lin, Hsin-Hui, 2000) and the mode illustration of ecological evolution (ODUM, 1996), and analyzes the modes by the 27 investigation points between 248.7K~386K of the toward-north National Highway No. 3 with close construction periods.
In light of the results of this study, we could tell that different ant-erosion covering materials of being vegatated by net have different characters. And, in accordance with the quantified data of this study, the function differences shown by characteristic data could be specifically defined, which could be taken as not only the basis of the quality control for applying similar materials to engineering application practically, but also the basis of choosing the materials of the engineering of being vegatated by net on sloping fields as well as the basis of designing the corresponding working methods.
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