路基土壤多位於地下水位以上，屬於不飽和土壤，當土壤受到季節性降雨及地下水位上升等環境變化，會使得路基土壤含水量濕化至平衡含水量，此現象往往會牽動內部基質吸力與土壤參數之改變。本研究為解此變化過程，採用自行研擬之設備及程序對試體進行濕化模擬試驗，探討濕化過程引致之基質吸力變化與土壤參數的關係。由試驗結果顯示，濕化初期，土壤參數改變對基質吸力有較大幅度之影響，於接近平衡含水量時，則影響趨於平緩。
一般路基土壤之最大剪力模數可作為勁度評估之指標，因此本研究亦探討濕化下，最大剪力模數與其它土壤參數與之關係及相關性。另外，本研究研擬一套不飽和三軸試驗設備，運用軸平移技術以便能直接了解基質吸力變化對路基土壤參數之影響。試驗結果顯示，乾側試體初期的最大剪模數最高，而濕化後乾側有較大幅度降低，而使得OMC試體最高，而基質吸力對最大剪力模數確實具有高度之相關性。

The subgrade soil often lies above the groundwater level and appears in unsaturated conditions. Since the subgrade soil is affected by the seasonal rainfall or the groundwater changes, the long-term water content of subgrade soil would increases to Equilibrium Moisture Content. This result often causes the matric suction and parameter in soils to change.
In order to understand this variational process, this research used wetting simulation test by the equipment and process developed by ourselves. It could discuss the relationship between the matric suction and parameter changed. The test result showed a big influence between matric suction and parameter in soil at the beginning of the wetting process. While the water content was very close to equilibrium moisture content, this influence tended to steady.
In pavement engineering, the maximum shear modulus could assess the stiffness of pavement. Therefore, this research discussed the relation between the maximum shear modulus and the other parameters for understand their relationship. This research also developed a axis-translation technique of unsaturated soil triaxial apparatus which could control different matric suction. So we could understand the influence of matric suction changed for the soil parameters directly. The test results showed: the dry of optimum sample had the highest maximum shear modulus at beginning of wetting process, but the maximum shear modulus of it decreased quickly after wetting process .So the maximum shear modulus of optimum sample became the highest. And the matric suction had high relationship with the maximum shear modulus.

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