BACKCALCULATION MODULUS FULL
The analysis results demonstrate that assuming full bonding, instead of actual interface conditions of asphalt-stabilized base layer, moduli of stabilized base layers is underestimated, up to 2.5 times smaller than the original values. In this model, the viscoelasticity theory is employed to describe the displacement hysteresis, and the multipopulation genetic algorithm (MPGA) is used to iterate the optimal results. These deflection data are used to backcalculate pavement layer moduli, which are then used to determine the number of allowable passes and the allowable load.
Finally, the backcalculated layer moduli and the original moduli values were compared. This paper presents a new model for modulus back-calculation for high liquid limit clay subgrades. It is necessary to investigate the effect of the distresses on the deflection basin and the backcalculation modulus. With deflection time histories from a typical FWD test, it was possible to backcalculate the relaxation modulus curve, E(t), up to about t 10 1 s and the complex modulus curve, E, from f 10 3 Hz and above. Based on in-situ FWD testing and laboratory dynamic modulus test, the influence of loading level, position and pavement temperature on FWD back calculated modulus and the relation between bacalculated modulus and dynamic modulus was analysed. However, the FWD test has sometimes been performed on asphalt pavement with distresses such as cracking.
Backcalculation of asphalt concrete moduli using field-measured strain. Most backcalculation analyses assume pavements to be continuous, homogeneous and intact. to predict the layer moduli using backcalculation process based on deflection data measured by LWD tests. Secondly, different friction coefficient values between asphalt layer and stabilized base layer were introduced into dynamic finite element model, accordingly, deflection basin parameters were calculated and layer moduli are determined based on the established regression functions. Asphalt Concrete (AC) modulus is a critical component of mechanistic-empirical.
Then, the regression functions between deflections basin parameters and layer moduli were created and used to backcalculate layer moduli. Firstly, according to the full bonding hypothesis, a dynamic finite element analysis model was established to generate a synthetic surface deflection database of the semi-rigid asphalt pavements. The objective of this study was to analyze the errors in layer moduli backcalculation due to modeling of layer interface condition. The dynamic moduli predicted from the measured resilient moduli with the trained ANN were found to be reasonable compared with the measured dynamic moduli.To make appropriate rehabilitation decisions, determining structural layer moduli of the existing semi-rigid asphalt pavements is a crucial task for highway engineers. The ANN model was verified with four 12.5-mm surface course mixtures with different aggregate types and binder types and one 25.0-mm base mixture. By using their prediction method, this study proposes the population of a database of measured dynamic moduli with the corresponding predicted resilient moduli to train an artificial neural network (ANN). Conventional backcalculation methods mainly use the peak values of FWD deflections to backcalculate linear elastic modulus for each pavement layer (Huang. Other investigators have presented evidence that the resilient modulus can be predicted from the dynamic modulus by using the theory of viscoelasticity. Thus, such databases must convert their data to the currently accepted standard (i.e., |E*|). This is a significant change from the resilient modulus used in the previous AASHTO "Guide for the Design of Pavement Structures." One of the challenges of changing the material characterization is that databases, such as the Long-Term Pavement Performance Materials Database, contain older material characterization information. The NCHRP Project 1-37A "Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures" introduces the dynamic modulus (|E*|) as the material property for the characterization of hot-mix asphalt mixtures.