| The flexible base is the necessary supplement to simi-rigid base for its excellentperformance. Its stress in the structure layer, which is caused by the vehicle load, is changedcertainly with the increase of depth of asphalt layer against the simi-rigid base. Under thecondition, it is a problem that calls for immediate solution in order to do the adoption andapplication of asphalt pavement with flexible base.The indexes of deflection, compressive strain on the top of subgrade and tensile strain onthe bottom of asphalt layer, couldn't reflect the real pavement distress. The indexes of therutting, Top-Down crack and reflecting crack are proposed as the pavement design indexbased on the distress of asphalt pavement with flexible base. The performance forecastingmodels of asphalt pavement with flexible base are built. Upon the above research, the ruttingdepth and fatigue life of pavement are calculated. At last, taking Qindao-Yinchuan freewayfor instance, the rutting depth and fatigue life which originate from the Top-Down cracks andreflecting cracks, are calculated.The dynamic modulus and phase angle of three kinds of asphalt mixture are determinedbased on the Frequency Sweep Test at different temperatures. In accordance with thetime-temperature equivalence principle, the master curves of dynamic modulus and phaseangle are determined through the applying of WLF equation and Sig-moidal function. Uponthe above research, the viscoelastic parameters of the generalized Maxwell model arecalculated by the Fourier transform. The achievements lay foundations of the ruttingcalculation. Moreover, the relaxation modulus determined by the test must be transformedinto bulk modulus and shear modulus in order to be applied by the finite element calculation.In view of this, the three-dimensional constitutive equation of generalized Maxwell model isdeduced. The coefficients of creep function are determined by the residue theorem. Uponthe above research, the expressions of bulk modulus and shear modulus are confirmed. At thesame time, the modulus of subgrade and simi-rigid material is backcalculated through the BPneural network according to the FWD. At last, the modulus of asphalt mixture are calculatedunder the circumstances of the certain vehicle speed and thickness of structure layer, based on the Frequency Sweep Test and considering the definition of effective depth. The above studiesprovide necessary parameters for the performance forecasting of test road.When the rutting is numerically computed by using a commercial FEA program, ANSYS,the probability of loading at different pavement position is calculated according to theprobability and statistics theory under the circumstances of the different wander distance. Fivefactors including the magnitude of wheel loading, the wander distance, the speed of wheelloading, the number of load repetitions, and the modulus of subgrade are studied to evaluatetheir contributions of rutting development for asphalt pavements. The significance that eachfactor impacts on the rutting is analyzed in order to offer necessary, support for the pavementdesign and maintenance in the future.When the fatigue life derived from the Top-Down crack is calculated, the load is appliedto the FEA model according to the rule of normal distribution. The improved Parisexpressions and fourth-order Runge-Kutta principle are adopted to calculate the fatigue life ofcorresponding pavement structure at different loading position and cracking position. On thebasis of this, the whole fatigue life derived from the Top-Down crack is calculated accordingto the Miner damage principle.The fatigue life derived from the reflecting crack is calculated according to the Minerdamage principle, considering the factor that the development of the top for crack is differentwhen a vehicle load passed the crack.At last, taking Qindao-Yinchuan freeway for instance, the rutting depth and fatigue lifewhich originate from the Top-Down cracks and reflecting cracks, are calculated.
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