Permanent deformation in ballast layers is a major contributing factor to the railway track geometry deterioration. In spite of a considerable amount of research on understanding and predicting performance of ballast layers, accurately capturing their settlements remains a challenge. In order to contribute to solving this important issue, a new numerical method for predicting ballast settlements is presented in this paper. This method is based on the finite element (FE) method combined with a constitutive model that captures permanent deformation accumulation in unbound materials under cyclic loading. This allows predicting permanent deformations of large structures and at large number of load cycles in a computationally efficient manner. The developed constitutive model is validated based on triaxial test measurements over wide range of loading conditions. Stress state in ballast layers has been examined with a 3D FE model, for several embankment structures and traffic load magnitudes. The determined stress distributions and loading frequencies were used as an input of the constitutive model to evaluate permanent strains and settlements of ballast layer. The influence of embankment structural designs and traffic loading magnitudes on the ballast layers settlements is examined and the results obtained are compared with the existing empirical performance models.

The friction force for aircraft landing is mainly provided by the texture of runway surfaces. The mechanism underlying friction force generation is the energy dissipation of tire rubber materials during random excitation induced by asperities. However, the runway surface texture is deteriorated by cyclic loading and environmental effects during the service life of a runway, leading to loss of braking force and extension of landing distance. Additionally, when an aircraft lands on a wet runway at a high velocity, the hydrodynamic force causes the tires to detach from the runway surface, which is risky and may lead to the loss of aircraft control and runway excursion. Worn-out surfaces along with wet conditions increase the risk of poor control during aircraft landing. Accordingly, this study investigated three types of asphalt runways (SMA-13, AC-13, and OGFC-13). Surface texture deterioration was simulated using a surface texture wear algorithm. Kinematic friction models were established based on the viscoelastic property of rubber materials, power spectrum density, and statistics of surface textures. A finite element model was developed by considering a real rough runway surface and different water film depths (3, 7, and 10 mm). A comparison of hydroplaning speed was conducted between numerical simulation and former experiments. The effects of different factors, such as velocity, wear ratio, runway type, water film depth, and slip ratio, on the skid resistance of the runway were analyzed.

Viscoelastic characterisation of asphalt mixtures is an important component for modelling and performance prediction of flexible pavements. In this study, using spherical indentation testing for measuring the viscoelastic properties of asphalt is explored. Indentation testing may provide an interesting alternative to existing experimental techniques, as it is capable of characterising small material volumes. Thus, it may become a useful tool for the characterisation of thin asphalt layers and for the measurement of binder phase properties in-situ in asphalt mixtures. Spherical indentation tests are performed on two mastic asphalt (MA) mixtures, prepared with different mastic types. The shear relaxation moduli obtained from the indentation tests are compared with the ones measured with seismic and SuperPave Indirect Tensile (IDT) tests. A new statistical analysis methodology is proposed for viscoelastic characterisation of the mastic phase with the indentation tests performed on MA mixtures. The accuracy and sensitivity of the developed method are examined.

In pavement engineering, a variety of promising application technologies are found relying on a thorough understanding of the intrinsic (mainly dielectric) electrical properties of asphalt binder and concrete materials. Meanwhile, the electrical properties of asphalt materials can be further enhanced by introducing conductive additives into and it has been brought to light that, the electrically conductive asphalt is becoming an emerging subject of interest that caters to the concept of a multifunctional pavement future. In context of these, this paper presents a holistic overview of the intrinsic and enhanced electrical properties of asphalt materials, including the theoretical analyses, as well as the corresponding applications in the practice. From such a state-of-the-art review, it is worth noting that: i) an improved understanding of asphalt material has been achieved by an in-depth examination of its electrical properties; ii) the increased significance of the research domain as a whole and, the key importance of multidisciplinary collaborations for future successes, have been indicated.

The electrified road (eRoad) system, which allows for delivering electric power to electric vehicles (EVs) while driving, has gained worldwide interest as part of future EV-charging infrastructure network. Being one of the promising solutions in an eRoad application, the inductive power transfer technology has been under active investigation and many prototypes have been demonstrated in pilot test sites around the world. However, from the infrastructural point of view, the possible modifications of the road structural and material designs, the changes in construction and maintenance practices, and the unclear long-term environmental impacts are threatening its sustainable implementation. In order to tackle these emergent gaps, feasibility analyses are accordingly conducted in this study and, based on which, some practical recommendations are summarized.

Aggregate segregation in asphalt mixture is a bothersome engineering issue during pavement construction. The practitioners have some measures to mitigate the segregation potential based on experiences which, however, can only reduce the risk to a certain extent. In this research, the authors aim to contribute to the discussion in a rational non-empirical way, by using novel experimental and numerical techniques. A case study is carried out to investigate the vibration-induced segregation in asphalt mixtures, corresponding to the circumstance arising during material transportation to the construction site. A novel experimental test is conducted for evaluating the segregation characteristics of asphalt mixtures under vertical vibration in laboratory conditions. A numerical investigation based on discrete element method is further performed to study the phenomenon from a micromechanical point of view. The obtained experimental and numerical results indicate that vibratory loading induces aggregate size segregation in asphalt mixtures, and the degree of segregation is influenced profoundly by the adhesive properties of bituminous binders and the aggregate gradation.

The mechanical behaviour of uncompacted asphalt mixtures is still not well understood,threatening directly to the pavement practices such as control of mixture’s workability andsegregation. This situation may become even worse due to the gradually increasing complexityand advances in paving materials and technologies. This study adopts a slump flow testbased on concrete technology and a Discrete Element (DE)-based numerical tool to investigatethe mechanical behaviour of uncompacted asphalt mixture from a microstructural point ofview, particularly focusing on the bituminous binder effects. The combined experimental andnumerical analysis indicates that bitumen distinctly influences the contact interactions withinthe mixture and thus its macroscopic flow, which can be physically interpreted as a combinedeffect of lubricated friction and bonding force. Additional case studies demonstrate that the DEmodel is capable of simulating the flow response of asphalt mixtures under changed particlecontact conditions and driven force.

The widespread use of Electric Vehicles (EVs) has been one of the main directionsfor pursuing a sustainable future of road transport in which, the deployment ofthe associated charging infrastructures, static or dynamic, has been included as oneof the main cornerstones for its success. Different electrified road (eRoad) systemswhich allow for dynamic charging of EVs by transferring electrical power from theroad to the vehicle in-motion, either in a conductive or contactless way, are underactive investigation. One of the important tasks in feasibility analysis of suchinfrastructure is to quantitatively assess its environmental performance and, thus,the consequential influences to the sustainability of road electrification as a whole.Having this concern in mind, in this study, a systematic LCA study is carried out in which the environmental impacts from the different life cycle stages have beencalculated and compared among several promising eRoad systems. In a next step,suitable strategies can be accordingly made to minimize these impacts in a most effectiveway; and more importantly, the LCA results of this study can serve as one ofthe important bases for conducting a more comprehensive and objective evaluationof the potential environmental benefits EVs could bring.

The primary objective of this study is to advance the understanding of the low temperature self-healing character of asphalt mixtures under different damage degrees, thus to determine the effective strategy of asphalt pavement maintenance. Firstly, three kinds of asphalt mixtures are selected to conduct the indirect tensile (IDT) fatigue test to a certain fatigue damage degree at low temperatures, and then the resilient modulus (Mr) at different rest time is measured to quantify the healing potential. Next, the fatigue loading with different intermittent time (0 s, 1 s and 3 s) is applied to determine the impact of intermittent time on healing potential. The results indicate that the descending order of healing potential of asphalt mixtures is: SMA-11 > AC-8 > AC-11 at 5 degrees C and -5 degrees C. The loading intermittent time has an obvious effect on the fatigue damage state of asphalt mixtures, while the longer the intermittent time, the less the effect on fatigue damage healing. Besides, the fatigue damage state has great influence on its healing potential of asphalt mixture. Under the low damage conditions, the initial healing rate is greater than the long term healing rate. However, the low temperature (-5 degrees C) dramatically reduces the healing rate of asphalt mixtures, and causes their long-term healing rate to stabilize gradually to a very low level. Especially under the high fatigue damage conditions, the healing potential of asphalt mixtures will almost disappear at -5 degrees C. Furthermore, together with meso-scale Computed Tomography (CT) scanning technique, it is found that the intemal crack distribution characteristics of different graded asphalt mixtures are different even under the same damage degree, which may explain the differences in the healing potential of asphalt mixtures. The use of a fast two-dimensional (2D) scanning technology further confirms that the crack zones inside the asphalt mixture are gradually shrinking after a period of high temperature healing. Finally, the Grey relational analysis reveals that the healing time has the most significant influence on the healing potential of asphalt mixtures. The gradation type and temperature have the similar influence level on the healing potential. The correlation degree between the fatigue damage degree and healing potential is the smallest compared with the other three factors. All rights reserved.

Given its promise for enhanced sustainability, electrified road (eRoad) has become a realistic option to support the clean and energy efficient Electrical Vehicles (EVs). To investigate the structural implications, this study focuses on a promising eRoad system which is a dynamic application of the Inductive Power Transfer (IPT) to provide electrical power wirelessly to EVs in-motion. A computational study is made in which, via a series of Finite Element Modeling (FEM) analyses on the eRoad structural response under various rolling conditions, is found that eRoads could have quite different pavement performances comparing to the traditional road (tRoad). Importantly, harsh loading due to vehicle braking or accelerating could incur higher potential of premature damage to the structure, whereas sufficient bonding at the contact interfaces would improve the structural integrity and delay the damage risks. In addition, localized mechanical discontinuities could also be a critical threat to the performance of the overall structure. To ensure that eRoads fulfill their sustainability promise, it is thus recommended that more focus should be placed on the possible measures, such as new structures and materials, to improve the structural integrity and thus the overall pavement performance of the integrated system.