Optimal Design For Perpetual Alsphalt Pavement On Wet Soft Sugrade

The structural parameters of pavement supporting system, composed by sub-grade, cushion and sub-base, have a direct influence on the stress condition and long-term performance of pavement. Because the high underground water table section silt sub-grade is always in moist condition, its poor bearing capacity can not satisfy the design requirement of sub-grade and pavement, the roadbed is necessarily to be consolidated to form a stable and strong supporting system with base layer. Therefore, based on the long-term performance of asphalt pavement, an integrated optimum design of pavement supporting structure in wet areas is proposed in this paper.Firstly based on the theory of unsaturated soil, the moisture content and resilience modulus of high underground water table section silt sub-grade are analyzed and forecasted via given models. The correlationship between compressive strain on top.of sub-grade soil and pavement deflection of normal asphalt pavement and durable asphalt pavement is established by finite-element analysis, and also the relationship between compressive strain on top of sub-grade soil and cumulative equivalent axle loads (the relationship between soil base top pressure strain design equation) on the basis of given relationship.The pavement supporting system parameters causing influence on stress condition and long term performance of normal asphalt pavement and long-life asphalt pavement is analyzed by finite-element method. And also analyze the influence on top roadbed compressed strain, the deflection on the surface and bottom layer tensile stress of asphalt pavement by sub-grade modulus, modulus and depth of sub-base and treated raodbed layer. The optimum thickness of treated roadbed layer is optimized in accordance with sub-base thickness and modulus under different conditions of sub-base and treated raodbed layer modulus. Finally, according to the reasonable modulus and the material prices of sub-base and treated roadbed layer, the optimum design of the asphalt pavement structure in wet areas is proceeded by finite element program, and then the most economical structure composition of asphalt pavement supporting is determined.