Perpustakaan Digital ITB

ASSESSMENT OF PAVEMENT STRUCTURAL CONDITION USING DEFLECTION BOWL ANALYSIS, Fermy, 1994, Program Magister Sistem dan Teknik Jalan Raya, Fakultas Pascasarjana, Institut Teknologi Bandung. The performance of 3-layer flexible pavement systems consisting of asphalt, unbound granular, and subgrade layers has been assessed under standard wheel load by using deflecton bowl analysis. The pavement and its foundation were modelled as a layered linear-elastic system. Layer thickness, loading arrangement and Poisson's ratio were kept constant. Modulus values of the layers were varied and a total of 77 pavement systems reflecting various combinations of modulus values was evaluated. The BISAR computer programme was used to calculate vertical and horizontal strains at 10 depths in the pavement, and at 7 horizontal locations corresponding to the location of deflectors of the FWD, i.e. at 0.0 m, 0.3 m, 0.6 m, 0.75 m, 0.9 m, 1.2 m, and 1.5 m from the center line of load application. Deflection was calculated by numerical integration of vertical strain with depth from the surface. The deflection bowl was obtained for each system by plotting surface deflection at each horizontal position. Parameters calculated and analysed were Maximum Surface Deflection (Dmax), Surface Curvature Index (SCI), Base Curvature Index (BCI) (pm), asphalt tensile strain and subgrade compressive strain (pm/m). The data indicate that the zone of influence of each layer of the 3-layer pavement system on the deflection bowl can be identified. The significance of individual deflection bowl parameters for the different pavement layers has also been identified. Correlations are developed between deflection bowl parameters and between these parameters and the two critical strains. Unique linear relationships were found between Dmax and subgrade compressive strain, and between SCI and asphalt tensile strain which appear to be independent of layer moduli. Correlation of BCI with asphalt tensile strain was poor. Linear relationships were found between Dmax and SCI for classification on the basis of the same value of El and E; and between Dmax and BCI for classification based on the same value of E; , Non-linear relationships were found between Dmax and asphalt tensile strain, and between SCI and subgrade compressive strain for classification on the basis of the same value of Ea. The data were found to be in good agreement with classification of pavement condition proposed by JERMYN and REINSLETT. These relationships can be used to indicate structural condition of the pavement, to make easier the prediction of asphalt tensile strain and subgrade compressive strain and to check the results of FWD test