Selection of Inertial Point for Asphalt Pavement and Backcalculation Method of Subgrade Modulus

Abstract:

It is realized that there exists a point called the inertial point in the pavement deflection basin whose deflection does not vary with the modulus of the upper layer, provided that the subgrade modulus and the upper layer thickness remain unchanged in cement concrete pavement. In order to make the theoretical deflection basin and measured deflection basin match each, the writer of this paper takes the rigid substratum into the calculation of theoretical deflection basin. As a result of a significant amount of calculation, the writer found it’s very difficult to get inertial point in asphalt pavement structure. Since that, the writer developes a new method of selecting inertial point based on smallest criterion of root mean square error and applies it to the back calculation of the subgrade modulus. It is found that the value of base modulus contributes more to the precision of subgrade modulus backcalculation and the writer draws a conclusion about the relationship between the inertial point parameters and the structure information on both flexible base and semi rigid base. The writer demonstrates the precision of the induction formula theoretically through the back calculations in different pavement structures, the precision and the reliablility of subgrade modulus backcalculation method based on inertial point using measured deflection basin are verified by a comparative study of the backcalculation programs at home and abroad.