Study For Structures And Design Methods Of Full Flexible Long Life Asphalt Pavement (FF-LLAP)

Over the world, the traffic load and volume are increasing fast with the rapid economic growth, especially the number of heavy truck. So the actual using life of asphalt pavement becomes shorter and shorter. Because of this, new changes for asphalt pavement are brought forward. Since the 20^th century, long life asphalt pavement (LLAP) has become a hot field of study in many countries, such as American, Europe, Canada, Australia, South Africa. Based on our Chinese conditions, using the Linear Elastic Multi-layer Theory, the paper studies the representative FFAP structure and design methods with flexible base and sub-base, which is termed Full Flexible Long Life Asphalt Pavement (FF-LLAP) in the paper.In the first part of the paper, a reasonable, general design indexes and criteria are put forward for FF-LLAP. Respectively they are: fatigue limit (the flexural-tensile strain limit under asphalt layer), pavement surface bending limit, and maximum shear stress in asphalt layer. The methods to determine the design indexes are given too.In the second part of the paper, the representative FF-LLAP structure is put forward based on the mechanics response regularities of the three-layer FF-LLAP. Based on the mechanic regularities of asphalt layer of three-layer FF-LLAP structures, the asphalt layer is divided into three layers. The mechanic demanding and thickness range are put forward tooIn the third part of the paper, based on the theoretical analysis of the relationship of parameters and design indexes for FF-LLAP structures, the paper put forward the mechanics analysis models and thickness design methods for FF-LLAP structures. Based on the analysis of FF-LLAP structure, the thickness design flowchart is put forward, and an easy and quick thickness design method was given out by looking up a series of thickness-determining charts.In the fourth part of the paper, a series of control indexes are put forward based on the layer function contribution, and used to study the unifying FF-LLAP structure design and material design. According to two layer functions of structure performance and functional performance, a series of controlling indexes are put forward based on the layer contribution and used to unifying the structural design and material design. The study shows that choosing primary material and mix design are two major aspects of the design methods. With different layer functions choosing, the controlling indexes are different too.In the fifth part of the paper, the paper put forward a reliability design and optimizing method based on the reliability theory and the characteristic of FF-LLAP. The paper puts forward reliability probability model, resisting probability model and effecting probability design parameters of FF-LLAP, by using Monte Carlo Method to calculate the structure reliability. Based on the reliability optimizing theory, the reliability optimizing model and constrains for FF-LLAP are put forward considering structure reliability, using performance and economic performance during the whole design period.In the sixth part of the paper, using the FF-LLAP structure design method is put forward in the paper, three LLAP trial pavement sections constructed in Binzhou of Shandong in 2005 are analyzed from follow aspects: mechanical indexes, dynamic parameters, material choosing and combination designing, structure reliability etc. So the feasibility and reliability of the methods put forward in the paper are checked.Based on the theory and example analysis, the study shows that the FF-LLAP structure design method is reasonable, and the reliability design and optimizing methods are feasible.