路基為公路之基底，支持面層結構，以達成負荷交通之任務，然而路基土壤受到水及交通荷重的聯合作用時，將使鋪面層產生損壞並降低鋪面服務水準進而減少鋪面使用壽命。因此，本研究利用A-7-5凝聚性路基土壤在不同含水量狀態下之反覆載重試驗結果，建立回彈應變迴歸式及永久應變迴歸式，然後使用ABAQUS有限元素程式進行在不同載重條件下以省道斷面為例之三維柔性鋪面結構分析，由所得之路基土壤受力狀況配合回彈應變迴歸式，探討路基土壤在不同含水量狀態下對應之回彈模數，據以評估不同交通荷重作用下路基土壤在不同含水量狀態時對鋪面結構及其成效之影響。另外，採用ABAQUS有限元素程式所提供之Mohr-Coulomb塑性模式進行鋪面結構分析，探討路基土壤在不同含水量狀態下使用彈性模式與塑性模式對鋪面結構分析之影響，並推算路基土壤之永久變形。 分析結果顯示，當路基土壤含水量增加時對鋪面結構分析之影響隨之增加，而隨軸重加倍及胎壓增加時，路基土壤含水量變化對鋪面結構之影響也隨之增加。且路基土壤在高含水量狀態下承載能力降低，因此造成抵抗車轍之能力降低，使鋪面損壞受車轍所控制；而在含水量為OMC狀態下，路基土壤承載力佳，故較易發生瀝青層之疲勞損壞。而路基土壤之含水量較高時，使用彈塑性模式所得垂直位移、水平應變與垂直應變皆較彈性模式為大，且隨軸重增加，兩模式之差異隨之增加，但影響範圍侷限在基層及路基，而對瀝青層並無顯著影響。 The resilient modulus and cumulative permanent strain of subgrade soils under various traffic and environmental conditions are important considerations for the design of a pavement against fatigue and rutting failures. A simple model was developed to evaluate the resilient modulus and accumulated permanent strain of cohesive subgrade soils at different moisture contents under repeated loads. The empirical model was derived from the observed behavior of an A-7-5 cohesive soil. Then the response of the pavement and the corresponding resilient modulus of subgrade were calculated under various traffic and environmental conditions using the three-dimensional finite element program ABAQUS. The study also compares pavement response using elastic and elasto-plastic subgrade material models. The results reveal that subgrade at higher moisture content has a larger influence on the pavement response. As axle load and tire pressure increase, changes in subgrade moisture content on pavement response become more pronounced. Pavement failure is controlled by the permanent deformation when the subgrade is at high water content; while it is controlled by the fatigue cracking when the subgrade is at optimum moisture content. In addition, strains in the pavement system obtained using elasto-plastic subgrade material model are higher than those obtained using elastic model.
