目前柔性鋪面的設計仍以經驗法則為主要依據，但美國發展中的2002 年鋪面設計準則已確定將採用力學法則。目前用於鋪面設計的少數力學-經驗方法係基於下列假設，因而使這些方法受到許多限制：(1) 各鋪面結構材料均為線彈性(linear elastic)；(2) 永久變形係依據路基土壤頂部之彈性應變進行評估，而未將材料永久變形特性列入考慮； (3) 疲勞裂縫係以面層底部之水平彈性應變來加以評估，而未考慮結構層厚度內的裂縫傳播行為。新一代的力學-經驗設計方法必須突破這些限制，因此需要對鋪面材料引進塑性、破壞力學及其他實際材料特性來預測車輛重覆載重下的車轍及疲勞裂縫。本研究因應新一代力學設計法的原則，針對鋪面成效預估所需之參數，發展取得路基土壤材料特性的程序及方法。預定將以三軸重覆載重試驗，建立路基土壤在交通載重條件下之應力-應變關係，並發展永久變形特性之力學模式。其中，為模擬現地路基土壤的服務狀態，將發展新的土壤試體製作方法，以浸水方式對土壤試體進行預處理，取得土壤的不同含水條件，並量測土壤吸力，以評估土壤吸力對回彈模數之影響；重覆載重試驗方面，則將進行10,000 次至 100,000 次的加載，以取得路基土壤永久變形累積特性。 Currently, the design of flexible pavements is based on the empirical approach. AASHTO and FHWA mechanistic pavement design method is being developed and expected to be available in 2002. Few mechanistic-empirical methods exist. They are based on assumptions that severely restrict their use: (1) pavement materials are linear elastic; (2) the permanent deformation is evaluated through the elastic vertical strain at the top of the subgrade, and the permanent deformation properties of the materials are not directly taken into account; (3) the fatigue cracking is evaluated through the elastic horizontal strain at the bottom of the asphalt layer, without consideration of crack propagation through the layer thickness. The new mechanistic approach would require that plasticity, fracture mechanics, and more realistic material properties be used to predict the rut depth and fatigue cracking with the number of load repetitions. This study aims at evaluating the parameters of subgrade soil needed for predicting pavement performance, and developing procedures to obtain the material characteristics describing these parameters. It is proposed that the stress-strain relations be evaluated under repeated stress level corresponding to traffic load. Based on repeated load test results, the permanent deformation of subgrade soil will be characterized. In order to simulate field situation, a new method for the preparation of test specimens by submersion will be developed. Besides, this study is undertaken to evaluate the effect of soil suction on resilient modulus of subgrade soil specimens. Subgrade soils are to be tested under different deviatoric stresses for 10,000 to 100,000 load repetitions. The accumulation of permanent deformation under repetitive loading will be characterized. 研究期間：9308 ~ 9407
