Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Flexible pavement


Assessment of the Accuracy of Road Flexible and Rigid Pavement Layers Using GPR

Hussein H. Karim; Ammar M. M. Al-Qaissi

Engineering and Technology Journal, 2014, Volume 32, Issue 3, Pages 788-799

Ground Penetrating Radar (GPR) is frequently used in pavement engineering for road pavement inspection. The main objective of this work is to validate nondestructive, quick and powerful measurements using GPR for assessment of flexible and rigid pavement thicknesses and detection of rebars and joints within the rigid pavement. To achieve this work, in-situ simulation model (1.2 m 1.2 m in dimension), consists of three layers (sub-base, flexible and rigid pavement), was made and surveyed by GPR using three antennas (250, 500 and 800 MHz). The interpretation results of 250 MHz antenna identify and assign the flexible pavement as one layer without identifying the rigid pavement layer. With the 500 MHz antenna, the flexible pavement appeared as one layer with identifying the rigid pavement boundaries. While using 800 MHz antenna, both flexible pavement and rigid pavement layers were clearly identified as in the in-situ simulation model. Therefore, the 250 and 500 MHz antennas have much more penetration, but much lower resolution. Besides, rebars and joints were clearly appeared in both 500 and 800 MHz antenna. By correlating in-situ model with radar GPR data, the results show thickness deviations (percentage error) on the order of 1% for surface layer and about 2% for both binder and rigid layers. Applying 500 and 800 MHz antennas perpendicular to steel reinforcement within rigid pavement, the rebars (with dielectric constant equal to 13.6 with velocity equal to 8.1 cm/ns) and joints (with width 0.025 m) appeared in the radargram. From the precise calculation of thickness, it can be concluded that an excellent correlation between field model and radar data.

A Finite Element Model for Rutting Prediction of Flexible Pavement Considering Temperature Effect

Mohammed Salih Abd-Ali

Engineering and Technology Journal, 2013, Volume 31, Issue 21, Pages 537-548

Permanent deformation in asphalt layers which manifestation on pavement surface is named rutting which represents one of the most significant distress of asphalt pavements. Different empirical models have been used to calculate permanent deformations which include traffic conditions and temperature effect. These empirical models were calibrated in a three dimensional finite element commercial software package. Finite element analysis through ANSYS computer software (version 11.0) was used to analyze three dimensional pavement structures and in order to investigate the impact of wheel load on rutting formation and pavement response considering temperature effect. In that model, the asphalt layer was assumed to follow a viscoelastic behavior by depending on dynamic modulus using Timm and Newcomb model. While, granular and subgrade layers were presented as linear-elastic perfectly plastic based on Drucker-Prager model. After insuring the model validation, the study investigated the effect of temperature on the rutting depth and plastic strain as a pavement response. The analysis of results showed that the rut depth and plastic strain increases with increasing the temperature.

Analysis of the Performance of Flexible Pavement under the Effect of Wheel and Thermal Loads

Mohammed Y. Fattah; a Abd. El-Ghany; Shayma; Ahmed S. Abdaljabbar

Engineering and Technology Journal, 2010, Volume 28, Issue 18, Pages 5782-5802

One of the major sources of distress in roads is the cracks that appear in flexible asphalt pavements. Combined wheel and thermal load induced cracking in the form of bottom-up and top-down fatigue cracking.
In this paper, combined effect of wheel loads and temperature is considered in finite element analysis of flexible pavement layers. The heat flow equations are derived and the program (ANSYS V 5.4) is utilized to carry out the analysis. The subgrade layer is modeled as an elasto-plastic material following Drucke–rPrager model for yielding of the isotropic material, while both the asphalt and base layers are
considered elastic. Three different thicknesses for the asphalt layer are tried; namely, 0.05 m, 0.10 m and 0.15 m, respectively. A temperature rise of 40 oC was considered in addition to wheel pressures.
It was found that an increase of wheel pressure from (500) to (700) kN/m2 leads to increase in vertical displacement of about (4 – 8)%. This increase becomes (10 – 22%) when the wheel pressure becomes 1000 kN/m2. The temperature rise leads to decrease in the effect of wheel pressure because temperature leads to expansion (upward movement) reverse to wheel load effect. The effect of wheel load is transmitted directly to the underlying subgrade within the wheel zone. The deformed zone under the wheel becomes larger when the load increases. The maximum displacement increases by about (24%) when the load is
duplicated.

Combined Effect ofWheel and Thermal Load Conditions on Stress Distribution in Flexible Pavement

Zainab Ahmed Alkaiss; Suham E. Saleh Al-maliky

Engineering and Technology Journal, 2009, Volume 27, Issue 12, Pages 2257-2267

The aim of this research is to study the behavior of flexible pavement under
wheel and thermal loading conditions using the finite element program ANSYS V
(5.4). The stress states distribution within the asphalt concrete pavement that
influence the direction of crack propagation have been investigated. The obtained
results from ANSYS finite element program show that a maximum stress intensity
factor value obtained at surface and then decrease with depth about (0.75 of
asphalt layer thickness) due to reduction in temperature in asphalt layer, which
indicates that crack will initiate at surface and extend throughout asphalt layer.
The horizontal stress for both top and bottom layers increase with the variation of
thermal coefficient expansion factor. High values of stresses at top surface of
asphalt layer due to high contact stress were induced under wheel and thermal
load conditions. As a result the highway pavement exhibited propagation of
surface –initiated cracks. Field observation of cores extracted from asphalt
concrete pavement confirmed the obtained results.