Measuring of thickness of the asphalt pavement with Use of GPR
The results of development, tests and application of the GPR for measurement of the road asphalt layers thickness are presented in the paper. Main necessary improvements providing the possibility of use the GPR as a measuring device are described as well as some results of application of the GPR for inspection of the road structure after reparation the road. It was achieved accuracy of layers thickness measurement better than 0.5 cm.
Subsurface object imaging with two types of RTR-differential GPR system
The main aim of this work is to analyze imaging possibilities of differential antenna systems that consist of transmitting antenna and a pair of receiving antennas symmetrically displaced with respect to the transmitting one a) along the direction of GPR movement; b) in the direction normal to the ground surface. To do this, radargrams are simulated by a specialized finite-difference time-domain solver. A modificated SAR approach is applied to process the synthetic differential data and to achieve object image.
Numerical analysis of surface crack propagation in flexible pavements using XFEM and cohesive zone model
Surface initiated (top-down) cracking in the longitudinal direction of pavements has become a predominant mode of failure in thick asphalt pavements. Most previous researchers studied crack propagation using the traditional Linear Elastic Fracture Mechanics (LEFM) method by calculating the stress intensity factor around the crack tip. In this paper, Extended Finite Element Method (XFEM) was used to study the key factors causing surface initiated crack propagation under surface tension and/or shear. A two-dimensional (2-D) finite element (FE) model for a two-lane flexible pavement was built to predict pavement responses and crack propagation potential under various scenarios. It was found that surface tension is the major driving force for crack propagation when the crack is at some distance away from tire loading. The results show that the distance from the location of crack to tire loading, the depth and direction of the crack, and the modulus ratio between the hot-mix asphalt (HMA) layer and the base layer have significant influences on crack propagation under surface tension. On the other hand, this study shows that shear stress can induce surface initiated crack propagation near the loading area as the shear resistance of material becomes low at the high temperature.