Multilayer Pavement Research Articles

Dynamic response of asphalt pavement under vibration rolling load: Theory and calibration

Vibrating compaction is a critical procedure to guarantee the quality of asphalt pavement, and the dynamic response of asphalt pavement is a complicate problem in the process of vibration rolling. This paper aims to theoretically investigate the dynamic response regulation and influencing factors of pavement under the moving vibration load. Firstly, based on the viscoelastic theory of multi-layer system, the dynamic response governing equation of asphalt pavement is established under the vibration load, the governing equation was then simplified by the two-dimensional Fourier transform method. Further, the stiffness matrices of the single-layer and multi-layer pavement structures are obtained by using the dynamic stiffness method. Consequently, the exact solution is obtained for the plane strain problem by programming and validated with the finite element results, which is proved to be more efficient in the calculation. Moreover, the model is calibrated by the field test to determine the wave number and dynamic modulus during the vibration rolling process. Subsequently, the effects of material and load frequency are investigated on the dynamic response in terms of acceleration and displacement. The results show that both of the acceleration and displacement of pavement surface vibrate periodically with the vibrating load, and the changing regulations of the acceleration and displacement with loading time can be divided into three stages corresponding to the engineering practice such as rapid decline, slow decline and stable stages. Finally, the influencing factors are analyzed in terms of the modulus of materials (i.e., surface course and base course) and the frequency of load. It shows that the peak values of acceleration and displacement of the pavement surface change significantly and nonlinearly with the material modulus in the form of power function. Meanwhile, the influence of vibrating frequency is also significant and a quadratic relationship between the acceleration/displacement and frequency. This paper provides an insight into understanding the dynamic response of pavement under vibration rolling condition to some extent, and potentially provides theoretical and technical support for accurately determining and modifying some indexes that characterize the compaction degree of asphalt pavement.

Evaluation of Permeable Brick Pavement on the Reduction of Stormwater Runoff Using a Coupled Hydrological Model

In several cities, permeable brick pavement (PBP) plays a key role in stormwater management. Although various hydrological models can be used to analyze the mitigation efficiency of PBP on rainfall runoff, the majority do not consider the effect of multi-layered pavement on infiltration in urban areas. Therefore, we developed a coupled model to evaluate the potential effect of PBP in reducing stormwater runoff at a watershed scale. Specifically, we compared the hydrological responses (outflow and overflow) of three different PBP scenarios. The potential effects of PBP on peak flow (PF), total volume (TV), and overflow volume (OV) were investigated for 20 design rainstorms with different return periods and durations. Our results indicate that an increase in PBP ratio reduces both PF (4.2–13.5%) and TV (4.2–10.5%) at the outfall as well as the OV (15.4–30.6%) across networks. The mitigation effect of PBP on OV is linearly correlated to storm return period and duration, but the effects on PF and TV are inversely correlated to storm duration. These results provide insight on the effects of infiltration-based infrastructure on urban flooding.

Artificial Neural Network–Based Inversion for Leaky Rayleigh Wave Dispersion Curve from Non-contact SASW Testing of Multi-layer Pavements

The air-coupled spectral analysis of surface waves (SASW) is an improvement technique of the conventional SASW method. The test can be used to evaluate the elastic modulus profile and layer thickness in the layered structures, such as pavement and soil ground. In air-coupled SASW test, the ground-coupled sensors are replaced by non-contact sensors to collect leaky surface waves, instead of the ground vibration. The evaluation is based on leaky Rayleigh wave dispersion characteristic in a layered media and then through a process of inversion which is considered a complicated process. This paper describes a development of an automated inversion procedure of non-contact SASW test data based on the neural network method. The effect of the structural properties of the pavement profile on the dispersion curves’ shapes was investigated too. The artificial neural network (ANN) models were trained by using a synthetic dispersion curves calculated from numerical simulation of different asphalt concrete pavement layer system configurations. The effect of the most optimized networks with the lower error rate and iteration number for convergence were selected and tested for certainty. The final results for the developed ANN models were reasonable and very close to the actual output.

THERMOELASTIC STATE OF MULTILAYERED ROAD PAVEMENT

This a review of the monograph “Thermoelastic state of multilayered pavements”, which presents the results of a computer analysis of stress-strain states of multilayered bituminous concrete pavements under the influence of transport loads with regard to seasonal and daily changes in ambient temperature. Based on the finite element model of pressure-heated deformation of coatings, we studied the mechanical behavior of the systems under consideration under various design schemes, loading conditions, the presence of cracks and concrete segregation, as well as rod and mesh reinforcement.The effects of stress concentration in the system due to high-gradient temperature fields and structural imperfections of the multilayered pavement are identified.

Design of smart wetting of building materials as evaporative cooling measure for improving the urban climate during heat waves

An urban microclimate model is used to design a smart wetting protocol for multilayer street pavements in order to maximize the evaporative cooling effect as a mitigation measure for thermal discomfort during heat waves. The microclimate model covers a computational fluid dynamics (CFD) model for solving the turbulent air, heat and moisture flow in the air domain of a street canyon. The CFD model is coupled to a model for heat and moisture transport in porous urban materials, to a radiative exchange model, determining the net solar and longwave radiation on each urban surface and to a wind driven rain model able to determine the wetting flux on each surface during a rain event. We first evaluate the evaporative cooling potential for different pavement systems during normal summer conditions after a long rain event during night in order to select an optimal pavement system. Then, we design a smart wetting protocol answering the questions ‘when’, ‘how much’ and ‘how long’ a pavement should be artificially wetted for having a maximum cooling effect. We found that a daily amount of 5mm wetting over 10 minutes in the morning, preferentially between 8:00 and 10:00 am, guarantees a maximal evaporative cooling for one day and night during a heat wave.

Mechanical Evaluation of Concrete Bridge Deck Pavement Systems

Abstract Asphalt pavement systems for concrete bridge decks must not only comply with requirements from traffic and environmental exposure but also provide protection of the concrete structures against corrosive attacks from water or deicing agents. These multifunctional expectations are major challenges not only from the material side but also from the experimental side as to the evaluation of the right test methods for assessing the mechanical behavior of the whole multilayer pavement system. In this article, the results of a research project comparing different asphalt pavement systems for alpine regions are presented. These systems consist of hot rolled and mastic asphalt for wearing and protection layers placed on waterproofing systems with polymer bitumen sheets, liquid polymer, and mastic asphalt. The study revealed both the mechanical differences between the different systems and the weaknesses or strengths of different mechanical tests, clearly demonstrating that one has to be careful in interpreting seemingly contradictory results of different test methods. In particular, it was interesting to see that the rutting assessment for some systems differs between cyclic compression tests and rutting tests conducted with a model mobile load simulator.

Mechanical characterisation of interface shear strain of multi-layer composite pavement

ABSTRACT As interface bonding is a weak part of multi-layer composite, it is necessary to take a research on interface bonding mode of asphalt pavement overlay on cement concrete structure, which include: common bonding, super bonding and stress absorbing layer (SAL) sandwich. The strain gage method was used to collect strain values to evaluate the strain distribution at each of the following four locations: the middle of the asphalt pavement layer, the interface between the asphalt pavement concrete at the mid-span, L/4 span and fulcrum. There is a difference on the quantitative analysis of the strain distribution of bonding modes at each location. It can be concluded that strong bonding controls the force and deformation concentrated at the interface. It is also favourable to reduce the shear force and prevents extension at the interface. The results can explain well the mechanical characteristics at the interface in different bonding modes and provide technical support for the selection of overlay mixture and bonding mode.

Fractal evaluation of the rutting development for multilayer pavement by wheel tracking test

Rutting is a common form of pavement distress, consisting of the deformation of each layer in the multilayer pavement structure. To explore the development of rutting, two types of multilayer specimens, S1 and S2, were prepared in this study. A wheel tracking test was conducted for these multilayer specimens, and the rutting depths at various cumulative times were recorded by the testing device. Images of the vertical sections of the multilayer specimens at these cumulative times were also obtained in this study. The fractal dimensions of the full-depth specimen, top layer (TL) and bottom layer (BL) were calculated based on fractal theory. The calculated fractal dimensions of the full-depth specimen presented high correlation with the rutting depths obtained from the wheel tracking test. Then the deformation of the full-depth specimen and each individual layer can be evaluated by their corresponding values of fractal dimension. The results showed that the full-depth specimen and its TL and BL generally exhibited two stages, densification and flow deformation, in the wheel tracking test. In particular, deformations of the TL and the BL displayed simultaneously at the beginning of test loading and the deformation of the TL made impact on the performance of the BL. Among the two stages of rutting development, the TL made of AC-13 in S1 presented obvious densification during the first 45 min of the test, but this was not observed in the corresponding BL. However, the TL made of SMA-13 in S2 showed a longer duration and a lower deformation rate in the densification stage, and the densification was displayed in its BL for the first 30 min. In the flow deformation stage, the deformation rate of the BLs of S1 and S2 both made of AC-20 was similar, but the deformation volume of the BL of S2 was smaller than that of the BL of S1 finally. In addition, the contribution of the layers to deformation was examined. The contribution of the BL was generally larger than that of the TL on the rutting of multilayer pavement.

Instruments of granular matrix mechanics for solving design-level tasks on shear strength resistance of loosely-coupled material in cast stone pavement

The paper covers the method of distribution analysis for normal and shear stresses in a multilayer cast stone pavement design. The method is used to test the shear strength requirements. Some conclusions about the expediency of considering the granular matrix discrete structure applied in transport construction are made.

Dynamic Response Solution of Multi-Layered Pavement Structure Under FWD Load Appling the Precise Integration Algorithm

Dynamic Response Solution of Multi-Layered Pavement Structure Under FWD Load Appling the Precise Integration Algorithm

An Efficient Computation for the Multiaxial Viscoelastic Continuum Damage Analysis of Pavements

An efficient computation method that allows for evaluating the capability of pavement structures subjected to realistic loading conditions on fatigue cracking is important for pavement engineers. This study developed a fast and reliable computation algorithm, based on evaluating the fatigue cracking resistance of flexible pavements using the principle of the multiaxial Viscoelastic Continuum Damage Mechanics (VECD). For this purpose, a viscoelastic analysis was derived for the viscoelastic multilayered pavement systems under a moving load and used for integrating the multiaxial VECD model into the developed solution. Because of the analytical nature of the algorithm, stiffness reduction by means of pseudo stiffness could be directly evaluated at any location and at any loading repetition over a three-dimensional pavement structure. The resulted evaluation indicated that overall fatigue cracking performance of pavement structures could be assessed by the bottom pseudo stiffness; however, the probability of top-down cracking was high in pavement structures with thick asphalt layers.

Assessment of compaction quality of multi-layer pavement structure based on intelligent compaction technology

Intelligent compaction (IC) is an emerging and evolving technology for road construction. IC technology brings a lot of benefits as well as some challenges to be solved. This paper presents the framework of a field construction using IC technology and the results of the assessment of the practical use of intelligent compaction. The IC technology was implemented at the soil subgrade, the cement stabilized gravel subbase, and the cement stabilized gravel base course. The changing pattern of Compaction Meter Value (CMV) corresponding to roller passes and moisture contents of compacted materials was studied. It was found that it is more likely to achieve the desired compaction quality under the optimum moisture content situation. The relationships between CMV values and in situ measurements (compactness and deflection) for three layers were analyzed using simple linear regression analysis. The results of above linear regressions performed at three layers indicate the potential influence of underlying layers on upper layers. Then the relationships between CMVs of different layers were firstly studied using simple linear regression and multiple linear regression in which the effects of moisture content and compaction quality indicators were also considered. The study on the effect of moisture content on CMV shows that the closer the moisture content to the optimum moisture content, the more likely to get larger CMV values. The strong and consistent correlations between CMVs of different layers obtained from above regression analysis have further demonstrated the contribution of underlying layers to upper layers, and may be useful in the research of CMV decoupling in the future. Furthermore, the proposed moisture content effect study has provided a way for the above multiple factors involved CMV decoupling research in future studies.

Elastic multilayered pavement under an elliptical vertical load: analytical solutions and program verification

Since the linear elastic solution for multilayered systems was developed in the 1940s, it has been widely used to evaluate the soundness of pavement structure. The primary assumption in the analysis is that the load applied to the pavement structure is simplified as a cylindrical load. Hence application of the cylindrical load to the evaluation of pavement structure, which is well known to involve asymmetrical loading, has been limited. Therefore, the analytical solutions and program verification for an elastic multilayered system subjected to an elliptical vertical load (asymmetrical vertical load) are presented in this paper. A coefficient recursion method was obtained to derive the coefficients A, B, C, D, E, and F based on the general solutions of the asymmetrical class. The results show that coefficients E and F of an arbitrary layer are equal to zero for pavement structure under an asymmetrical vertical load. Then the asymmetrical vertical load was modelled as an elliptical vertical load by simulating the tyre ground pressure distribution. The analytical solutions were derived by substituting the Hankel-transformed load function into general solutions of the asymmetrical system. A C++ program (ASLAYER) was developed on the basis of the analytical solutions and verified by comparing the results with those of BISAR with the definitions and . The results show that ASLAYER can be used to make reliable estimations for the response of pavement structure under an elliptical vertical load. The results of mechanical responses for pavement structure under an elliptical vertical load, compared with those subjected to cylindrical load, show that the asymmetrical vertical load causes more damage to the pavement structure and should be given greater attention.

General surface loading over layered transversely isotropic pavements with imperfect interfaces

In this paper, we present an efficient and comprehensive approach to study the response of layered flexible pavements under general surface loading. Each layer can be transversely isotropic and the interface between the layers can be imperfect. Multiple surface loadings in both vertical and horizontal directions over circular regions can be applied. To handle efficiently multilayered pavements under very general loading and interface conditions, a new method called DVP (dual variable and position method) is proposed. The new method is computationally stable and can handle multiple imperfect interfaces very well in the multilayered pavement. The solution is further expressed in terms of the cylindrical system of vector functions so that the normal (dilatational) and shear (torsional) deformations can be separated and solved in terms of the LM- and N-types of this vector-function system. Various equivalent imperfect interface models are also investigated and their equivalence to the thin interface layer is further discussed.

Laboratory investigation of rutting performance for multilayer pavement with fiber Bragg gratings

Rutting is a significant problem for asphalt pavements, caused by factors such as channelized traffic and over loading, especially in urban areas and on highways. In recent decades, great emphasis has been put on this issue through various research methods. Fiber Bragg grating (FBG) sensing technology is widely used to detect the structure conditions due to its accuracy and simplicity and now gradually applied to pavements as a common detecting method. The objective of this study is to use FBG sensors to monitor the inner accumulated deformation of asphalt specimens in various depths at different temperatures, and seek for the relationship between accumulated deformation and temperature through an improved linear viscoelastic rutting prediction model. The results showed that the FBG sensors are reliable for monitoring accumulated deformation of asphalt pavements. For the full-depth rutting specimen, the deformation in the top and lower layer changed significantly with temperature. The middle layer had the largest unit accumulated deformation, which was not sensitive to temperature. It was also concluded that the revised model had enough accuracy to predict deformation of pavements, regardless of materials or structures.

Numerical modelling of flexible pavement incorporating cross-anisotropic material properties. Part II: Surface rectangular loading

In order to better understand the impact of increased loading on roads, studies on tyre-road interaction have gained prominence in recent years. Tyres form an essential interface between vehicles and road pavement surfaces. These are the only parts of the vehicle that are in contact with the road and transmit the vehicle loading to the road surface. The use of the Cartesian coordinate system is convenient in dealing with a uniform/non-uniform tyre load acting over a rectangular area, but few research reports are available that provide any form of theoretical solutions for pavement responses. This paper presents analytical solutions of responses due to rectangular loading acting on the surface of a multi-layered pavement system. The solutions developed incorporate both isotropic and cross-anisotropic material properties. The method followed is based on classical trigonometric integral and Fourier transformation of Navier's equations. Accuracy and validity of the solutions are verified through comparisons with a proprietary finite element method (FEM) package. For this purpose, a pavement structure composed of five main layers constituted by isotropic and cross-anisotropic (also known as transversely isotropic) material properties is analysed. In order to vary some of the layer properties with depth, the main layers were sub-layered, resulting in a 17-layer pavement system.

Assessment of the Remaining Life of Bituminous Layers in Road Pavements

In this paper, a mechanistic-empirical approach is presented for the assessment of bearing capacity condition of asphalt pavement layers by Falling Weight Deflectometer measurements and laboratory fatigue tests. The bearing capacity condition ratio was determined using past traffic data and the remaining fatigue life which was determined from multilayer pavement response model. The traffic growth rate was taken into account with finite arithmetic and geometric progressions. Fatigue resistance of layers’ bituminous materials was obtained with indirect tensile fatigue tests. Deduct curve of condition scores was derived with Weibull distribution.

Compare the Results Between Model Laboratory-test for Rigid Pavement and EverStressFE Software Analysis

EverStressFE is a 3D finite element modeling software that can be used to analyze the multilayer model pavement (up to four layers possible), which requires elastic modulus and Poisson's ratio of each layer as an input value. The purpose of this paper is to develop a comparison between EversStress-FE-based analysis and laboratory test results and determine the accuracy of the software. In this study, displacement and microstrain behaviors are compared. The vertical strain governing at both the top and bottom fiber of the concrete layer from the laboratory test are 38 and 44, respectively, compared to the EverStressFE result (gz<5.65) (in microstrain). Displacement at the center is 3.4 mm and 0.3 mm according to laboratory test and EverStressFE, respectively. The outcome shows that results of EverStressFE are approximately 10 times smaller than the laboratory test result in terms of displacement and microstrain, meaning that the software is not accurate to validate the laboratory test.

Characterization of Permanent Deformation of Asphalt Mixtures with Minimum Strain Rate, LVECD Program, and Triaxial Stress Sweep Test

The rutting resistance of asphalt concrete is typically assessed by using flow number tests in the lab in accordance with AASHTO TP 79. However, the flow number represents the rutting resistance of the material with regard to ranking for only a specific test condition. A significant amount of testing effort is needed to evaluate rutting resistance by using the flow number test under various loading conditions and temperatures. Therefore, researchers have developed alternative test methods to reduce the testing effort. For example, the incremental repeated-load permanent deformation test and the triaxial stress sweep (TSS) test are two promising protocols that can predict the permanent deformation of asphalt mixtures efficiently and accurately. This study compares the minimum strain rates (MSRs) obtained from incremental repeated-load permanent deformation and TSS tests to examine the ability of the TSS test to analyze the MSRs of asphalt mixtures. In addition, the viscoplastic shift model calibrated from the TSS test that is implemented in the layered viscoelastic pavement analysis for critical distresses (LVECD) program was used to predict the rut depths of 16 pavement sections from four sources. The MSRs and rut depths predicted from the LVECD program were compared with actual measured rut depths. The results of this study indicated that the MSR results could only be used to rank the rutting susceptibility of single-layer asphalt pavements. For a multilayered pavement system, structural level analysis is necessary to predict the accurate rutting performance and rut depths of the test sections.

An Assessment of Concrete Over Asphalt Pavement Using Both the Ultrasonic Surface Wave and Impact Echo Techniques

A portable seismic property analyzer (PSPA) was used to simultaneously acquire both ultrasonic surface wave (PSPA-USW) and impact-echo (PSPA-IE) data at predetermined locations along a section of multi-layered pavement. The pavement consisted of a basal concrete layer (∼220 mm), an intervening layer of hot-mix asphalt (∼60 mm), and a concrete overlay (∼220 mm). The section of multi-layered pavement was cored at multiple PSPA test locations for verification purposes. The conditions of the extracted cores were assessed visually, and the static elastic modulus, as well as the compressional wave velocity of each concrete overlay core, were measured in the laboratory. Results from this study demonstrated that the PSPA-USW tool can be used to evaluate the conditions of concrete overlay, the interlayer (hot-mix asphalt), and their bonding conditions from a qualitative perspective. A good correlation between the static and laboratory dynamic modulus from core specimens of concrete overlay were confirmed based on laboratory testing results. However, the field dynamic modulus of core specimens, based on PSPA-USW tests, was lower than both the static modulus and laboratory dynamic modulus. Furthermore, the PSPA-IE tool was not able to estimate the depth of the entire pavement and to various pavement layer interfaces due to the interference of flexural mode vibration. Fortunately, the difference between intact and deteriorated pavement can be qualitatively identified from the amplitude spectrum. More core specimens are needed for further studies in order to verify the performance of both PSPA-USW and PSPA-IE techniques for multi-layered pavement condition assessment.