Reflective Crack Propagation Research Articles

Stress Analysis of Asphalt Overlay on Old Cement Pavement by Impact of Rolling Technology

Cement concrete pavement road performance gradually decay with vehicle load and environmental factors in long-term effect. When the usability of the road surface reduces down to limiting bottom line standard, it can be used to repair asphalt overlay technique with the advantages of short duration, little impact on traffic road repair service and good performance. According to the force characteristics of old asphalt overlay concrete structure, this paper studies the impact of reflective crack propagation mode, fragments after impact on the asphalt overlay of the stress response with ANSYS finite element numerical simulation analysis, and it reveals the rolling technology can effectively reduce the impact of reflective cracking.

Simulation of Reflective Crack Propagation Path in Asphalt Overlay under the Partial Wheel Load

Partial wheel load is one of the main causes that lead to shear-type reflective crack of asphalt overlay in the old cement concrete pavement. Based on the theory of fracture mechanics and finite element method, this paper focuses on the numerical simulation of the reflective crack propagation path in asphalt overlay under the partial wheel load. Calculation result and analysis show that reflective crack partially expands upwards at the side of wheel load under the effect of partial wheel load with a sequential increase of crack propagation length. As the crack propagation length increases, stress intensity factors grow rapidly in the early period, and then increase by degrees slowly and, in the later period, the amplitude grows increasingly. Stress and strain fields enhance as the reflective crack increases upwards and the crack propagation angle expands gradually with the increase of reflective crack propagation length.

Numerical Simulation of the Reflective Crack Propagation Path for Open-Graded Large Stone Asphalt Mixes

Numerical Simulation of the Reflective Crack Propagation Path for Open-graded Large Stone Asphalt Mixes

Development, Calibration, and Verification of a New Mechanistic-Empirical Reflective Cracking Model for HMA Overlay Thickness Design and Analysis

The purpose of this paper is to present a new mechanistic-empirical (ME) reflective cracking model developed for hot-mix asphalt (HMA) overlay thickness design and analysis. After reviewing existing models, the reflective cracking model based on Paris’ law of fracture mechanics was considered as the state of the practice and was selected as the basis for the ME model development in this study. The model consists of stress intensity factor and fracture properties (A and n) as the fundamental input parameters for modeling reflective crack propagation caused by both traffic loadings (bending and shearing) and thermal effects (temperature variations). For practical application, 32 SIF regression equations were developed for HMA overlays with three levels of load transfer efficiencies (10, 50, and 90%) at joints/cracks under various traffic loading spectrums (bending and shearing) based on more than 1.6 million finite element simulations and computations. For the thermal induced reflective cracking, a “hybrid” approach, similar to the Strategic Highway Research Program low temperature cracking model, was proposed. In this hybrid approach, the viscoelastic properties of the HMA mixes were considered through the thermal stress at the “far field” (σVE-far), which then ties with the stress intensity factor (Kthermal) determined through regression equations. Also, the required fracture properties (A and n) can easily be determined in the laboratory using the overlay tester that has unique features with respect to specimen size, specimen preparation, and relatively short testing time (about 15 min). Additionally, the proposed reflective cracking model was preliminarily calibrated using three HMA overlay field-case studies, and then verified using California’s heavy vehicle simulator test results. Currently, more calibration is underway, but more field performance data are definitely needed for further model calibration and verification.

Accelerated pavement testing and modeling of reflective cracking in pavements

In the field of reflective cracking initiation and propagation in pavement structures, an Accelerated Pavement Testing (APT) has been developed. The numerical method is also supported. Numerical results obtained by calculations made with the finite element CESAR-LCPC software are then compared with the experimental data. The reflective cracking APT experience is the first step in the development of a new laboratory equipment to evaluate the design of bituminous layers to repair pavements. The experiment was performed on a 30 m track where eight discontinuities were established by cutting-off the sub-bases in order to ensure a crack development in the bituminous layer. The conditions that promote crack propagation were reproduced by the application of heavy periodic loads using the Fabac ALT-APT test rig. The width of the bituminous layer was decreased to facilitate the observation of the crack propagation, while avoiding creep of the material. The structure has a large number of sensors that measure longitudinal and transverse deformations at the bottom and at the surface of the bituminous layer. The deflections and the displacements are measured at several levels of the structure, as well as the temperature and the lateral edge cracking which is monitored by cracking sensors on both sides of the track. Preliminary results on two joints were used to determine the mechanisms of rupture of the structure. Four more tests with improved sensors have completed the information. Experimental and numerical results are compared in order to validate the analysis of the fatigue process (debonding, damage and cracking) in full scale pavement.

USE OF GEOTEXTILE AS A REINFORCEMENT FOR FLEXIBLE PAVEMENT OVERLAY

Pavement distresses are numerous and they differ in their shape, type, and origin causes.Cracking is one of the most commonly observed distresses in asphalt pavement. Hence if thesecracks reflect up to the new overlay, this reduce the service life and the serviceability of thepavement thus lead to a heavy burden on the exchequer. This investigation studies the effect ofreinforcing the new overlay by geotextile and its influence on the performance of pavement and onretarding the speed of reflective cracking propagation. So asphaltic beam specimens reinforcedwith two types of reinforcement (ALYAF PU 14 nonwoven geotextile and HaTelit c reinforcedgeogrid) in the middle as well as in the lower third of the beam depth were tested under the three -point bending test. The prepared beams include beams with and without initial crack to simulatethe cracked and uncracked layers in the field. The results of three - point bending test werecollected and analyzed by fracture mechanics parameters (fracture toughness KIC, GIC, and J-Integral) and crack depth ratio, Zr, at failure.Results show that involving the reinforcement can relevant the speed of crack propagation into thenew overlay and consequently prolong the economic life of the construction. Improve loadcarrying capacity via reducing the tensile stress peaks, absorbing some horizontal tensile stresses,and providing a uniform distribution of loads over a large area. Also HaTelit c geogrid appearedresults better than Alyaf PU 14 nonwoven geotextile.

Geogrid Reinforcing of Recycled Aggregate Materials for Road Construction: Finite Element Investigation

Economic advantages and environmental benefits encourage the use of recycled materials for road construction. Usually, however, these materials have lower stiffness and strength characteristics than typically used natural materials. Because of these inferior material properties, use of recycled aggregate materials for unbound road base construction may result in increased rutting, differential settlement, and reflective crack propagation. Placement of reinforcement between the underlying soil layer and the aggregate layer has been proposed to improve the load-carrying capacity of road bases constructed from recycled aggregate materials. To investigate the viability of such an approach, finite element analyses were performed of asphalt concrete pavements with base layers consisting of reinforced unbound recycled aggregate materials. The response of such pavements was compared with that of pavements consisting of unreinforced natural aggregates. The criteria chosen for comparison were the influence of the material characteristics of the recycled aggregate and the reinforcement on the development and speed of propagation of reflective cracking in the body of the pavement. Various combinations of reinforcement and aggregate material characteristics were simulated. It was concluded that the placing of reinforcement can reduce the speed of crack propagation into the top layer, improve load spreading in the unbound base layer, and prolong the economic life of the construction.

Procedures for analysis of strain transfer in the acetabular region in vitro

The failure of acetabular cups via loosening, migration or fracture is partially related to the stress distribution existing in the acetabular region. The complexity of the investigation of these stresses demands the application of a variety of model testing techniques involving combined embedded strain gauging, finite element analysis, transmission and reflective photoelasticity and crack propagation studies. The application of these procedures are described and the difficulties of obtaining representative loadings and restraints are commented upon.