Design Of Pavement Structures Research Articles

Resilient pavement design with consideration of flooding effect caused by climate change

Climatological reports demonstrate a clear trend of more frequent occurrence of extreme weathers. Flooding caused by heavy rains severely affects highway pavement performance in many coastal regions. As the trend of climate change continues, highway pavements in these regions will become more vulnerable to flooding. At present, however, pavement design is usually based on historical climatological data and seldom considers future climate changes. Moreover, traditional pavement analysis rarely considers the stochastic nature of weather. This study develops a life-cycle cost optimization model and adopts a stochastic approach to analyzing the effect of climate change. Pavement structure design is optimized by incorporating the flooding effect in the model. As a case study, hourly climate data in the past century in Hong Kong is analyzed to investigate changes in rainfall intensity, and the trends are used to optimize pavement design.

Evaluation of resilient modulus and unconfined compressive strength of subgrade

Subgrade soil is the important material as the foundation for supporting the pavement layers and the repeated load of vehicle traffic. To characterize the stiffness and strength behavior of subgrade due to traffic loading in structural pavement design can be determined by resilient modulus and unconfined compressive strength test. In this study, laboratory test of resilient modulus and unconfined compressive strength used to investigate (1) the effect of moisture content of the changes of stiffness and strength characteristics, (2) the correlation between the resilient modulus and elasticity modulus. The soil sample prepared at five type of compacted soils, at the dry side (OMC-20%OMC and OMC-10%OMC), OMC and at the wet side (OMC+10%OMC and OMC+20%OMC) . The result shows the moisture content has a significant effect on cohesive soil, the resilient modulus, modulus elasticity and stress value increase with the increase of moisture content until reaching the optimum moisture content (OMC) and then decrease with the increase of moisture content on the wet side of OMC point. By comparing both resilient modulus and unconfined compressive strength result from ANOVA statistics analysis can be concluded that there is no difference in stiffness between resilient modulus and modulus elasticity methods.

Study of the Permanent Deformation of Soil Used in Flexible Pavement Design

The decreasing supply of soils with geotechnical parameters suitable for pavement designs is a visible problem in our environment. In order to establish more efficient designs and adequate construction criteria, it is essential to understand the performance of materials. This is a study of the permanent deformation (PD) of soil used in pavement layers, obtaining prediction models through the technique of artificial neural networks, in addition to the design of pavement structures using mechanistic‐empirical and empirical methods. The multistage repeated load triaxial (RLT) test, as well as numerical analyses of stresses and displacements using the CAP3D program, was used. The results showed that both the test procedure and the prediction models performed satisfactorily in obtaining PD behavior. Moreover, designs using the methods adopted resulted in distinct structures, that is, thickness different from the granular pavement layers. It was concluded that the model and test procedure exhibit significant potential for characterizing and modeling the PD of granular materials.

High‐Temperature Rutting Resistance of Inverted Asphalt Pavement Structure

To improve the high‐temperature rutting resistance of asphalt pavements, an inverted asphalt pavement structure (IAPS), 4 cm AC‐13 mixture + 8 cm AC‐25 mixture + 6 cm AC‐20 mixture + 54 cm cement‐stabilized macadam, was proposed herein by considering engineering practice, theoretical calculation, and analysis. A rutting prediction equation of asphalt pavements was then proposed via rut‐development trends found by laboratory 18 cm thick rutting test. Subsequently, the rutting resistance of the IAPS was evaluated. The results show that, compared with the traditional asphalt pavement structure (TAPS), 4 cm AC‐13 mixture + 6 cm AC‐20 mixture + 8 cm AC‐25 mixture + 54 cm cement‐stabilized macadam, the maximum shear stress of the IAPS can be reduced by ∼1.7% along with improvements in rutting resistance by ∼16% and ∼12% under wheel loads of 0.7 and 1.2 MPa, respectively. Wheel‐load increase affects the rutting resistance of both structures in a similar manner: when the wheel load increases from 0.7 MPa to 1.2 MPa, the rut depths of both pavement structures increase by at least 63%. The IAPS clearly has better rutting resistance than the TAPS and is thus the better choice for asphalt pavement structure design.

Numerical investigation of the mechanical response of semi-rigid base asphalt pavement under traffic load and nonlinear temperature gradient effect

The effectiveness of any pavement design based on the mechanistic procedure depends on the accuracy of the mechanical parameters used such as stresses and strains. Hence, an effective and realistic prediction of these parameters when traffic and environmental data are provided is a step towards the future design of more sustainable pavement structures. This study investigated the distribution of the mechanical parameters in three new semi-rigid pavement structures with typical functional and structural requirements, specially designed to withstand various distresses of semi-rigid pavements. The response of these pavements to the combined effect of the nonlinear thermal gradient and moving axle load was examined by means of an advanced 3D pavement FE modeling. The model integrated mechanical and thermophysical properties of each pavement material, studied the transient dynamic effect of wheels load, and employed transient heat transfer and implicit dynamic analysis. Field measurements of these experimental pavement structures at the RIOH-Track test site in Beijing, China, as well as relative climatic data were used to verify and validate the accuracy of the developed model. Comparison of the numerical and experimental results indicated that the developed model predicted accurately the characteristic non-linear distribution of temperature along with the pavement depth and the pavement response to the combined effect of the nonlinear temperature gradient and traffic load. The influence of three main factors affecting the distribution of the mechanical parameters, namely; the bonding conditions between the pavement’s layers, the vehicle speed and the axle load amplitude were evaluated. In addition, fatigue analysis of the asphalt layers and the semi-rigid layers was performed to evaluate the theoretical service life of each pavement structure. The findings of this study underscored that the non-linear temperature gradient, despite being often neglected in mechanistic modeling, is a key parameter for accurate prediction of the distribution of stresses and strains in pavement system. Moreover, the results indicate that the lowest traffic speed and the extra weight extension of the truck axle have an adverse effect on mechanical parameters. Furthermore, the improvement of contact conditions at the interface results in good performance. Overall, the conclusions obtained in this study provides a reference for the design of semi-rigid pavement structures.

Sponge roads: the permeable asphalt pavement structures based on rainfall characteristics in central plains urban agglomeration of China

Permeable asphalt pavement should be selected according to the rainfall characteristics of the project site, so as to improve the permeable performance and ensure the bearing capacity of the pavement structure. Therefore, taking a city in the central plains urban agglomeration of China as an example, the characteristics of the rainstorm intensity distribution and cumulative rainfall are analyzed, and a combination scheme of drainage surface layer asphalt pavement suitable for rainfall characteristics in this area is proposed. Then, the pavement structure design is systematically carried out based on the permeable capacity and bearing capacity. The results show that under the rainfall conditions in this area, there is no surface runoff on the permeable asphalt pavement with 120 mm drainage surface layer, which is suitable for the medium traffic grade of urban roads with cumulative equivalent axle loads of 10 million to 12 million times.

Reasonable thickness design of expressway pavement structures based on gray relation analysis of subgrade soil improvement.

During the design of pavement structures, determining a reasonable thickness for pavement layers is critical. When an expressway is to be built in an area with a poor soil foundation, a reasonable subgrade treatment will make the pavement more durable. However, determining the optimal thickness of subgrade treatment is a difficult task for designers. A thicker treatment means a huge cost increase for the project, whereas a thinner treatment cannot achieve significant improvement in the mechanical behavior of pavement structures. This study used the finite-element method to analyze the mechanical response of real field pavement with subgrade treatments at certain depths. The study used an orthogonal design and gray relational theory to analyze the design indicators and make a better design for the pavement structure of a field expressway. The numerical calculation index and theoretical analysis results show that the treatment depth of subgrade soil has a significant influence on the stresses in an asphalt pavement structure and the bottom tensile strains of the asphalt layers. Therefore, designing a pavement structure with equal structural strength, using a reasonable depth for the cement-treated subgrade, instead of increasing the asphalt layer's thickness, is a more cost-effective solution.

Mixture Strength Class and Slab Dimensions’ Effect on The Precast Concrete Pavement Structural Performance

Mechanical properties and slab dimensions of concrete are the major parameters based on which the performance of concrete pavement structures is predicted. Precast concrete pavement, as one of the most common modular pavement type, is the advanced next-generation technology characterised as high quality, durable, quickly built and easily maintained. The service conditions of precast concrete pavement (traffic loading and environmental effects) are similar to the conventional cast-in-place jointed plain concrete pavement. Thus, the precast concrete pavement structural design is similar to that of jointed plain concrete pavement. There are several concepts for the design of concrete pavement structure. However, they are based on different distress evaluation and critical stresses estimation methods assuming the slab dimensions that for jointed plain concrete pavement are within the wide joint spacing range from 3.5−6.0 m. The objective of this paper is to analytically evaluate the effect of concrete mixture mechanical properties on the thickness and dimensions of precast concrete pavement slab. Also, define the minimal thickness of precast concrete slab dependent on slab dimensions and concrete mixture mechanical properties elastic modulus and tensile splitting strength. The analysis is based on bearing capacity, performance and fatigue boundary conditions as reported by semi-probabilistic pavement design method Richtlinien für die rechnerische Dimensionierung von Betondecken im Oberbau von Verkehrsflächen RDO Beton 09. Considering that, concrete mixture has significant effects on pavement performance; the composition of concrete was also discussed in this paper. The optimal slab dimensions, concrete layer thickness, and base layer type is suggested in this paper. The outcomes of this analysis apply to the production of precast concrete pavement slabs.

The resilient moduli of five Canadian soils under wetting and freeze-thaw conditions and their estimation by using an artificial neural network model

The resilient modulus (MR) is a key parameter used in the mechanistic-empirical methods for the rational design of pavement structures. In permafrost and seasonally frozen regions, the MR of subgrade soils is significantly influenced by the variations in moisture content and temperature. The MR typically reduces due to the weathering action associated with wetting and freeze-thaw (F-T) cycles, which contributes to the reorientation of soil particles, loss in suction and cohesion, and formation of cracks in the subgrade soils. In the present study, the MR values of five Canadian soils that are widely used as pavement subgrades were determined under wetting and F-T conditions. The key findings from the extensive experimental investigation suggest: (i) the MR values of the soils at their respective optimum water contents significantly reduce up to the critical F-T cycle, which is typically the first or second F-T cycles; (ii) there is little change in the MR values from the critical to the tenth F-T cycle; (iii) the percentage of reduction in the measured MR at the optimum water content after the critical F-T cycle is strongly related to the soils plasticity index; (iv) the measured MR values are typically low for the specimens subjected to wetting, and the effect of F-T cycles on these specimens is insignificant; and (v) the effect of stress levels on the MR values is dependent on the initial water contents of the specimens and soil types. In addition, an artificial neural network (ANN) model was proposed and validated for estimating the MR of the tested soils taking account of various influencing factors. Both the experimental data and the developed ANN model provide valuable information for the rational design of pavements in Canada.

Recommendation of Suitable Loading Waveforms and Wavelength Equations for Dynamic Modulus Based on Measured Wheel Loads

Dynamic modulus is a key parameter in the pavement structure design and analysis. A haversine loading waveform is the most widely recommended waveform in the laboratory to obtain the dynamic modulus of asphalt mixtures by test protocols, which may not completely represent all field loading conditions. The aim of this study is to investigate the suitable vertical compressive stress pulse waveforms at different depths under different pavement structures and to obtain the best fitting waveforms by using the least squares method. Specifically, the vertical compressive stress of different pavement structures was calculated by utilizing a three-dimensional finite element program incorporating with the measured wheel loads. The results revealed that the vertical stress pulse waveforms at different depths in asphalt layer were different within different pavement structure combinations. Generally, the square waveform fitted the vertical stress pulse waveform better for the shallow depth of the surface layer. The haversine waveform became more suitable while the depth increased. The bell waveform was better when the depth went deeper (i.e., 10 cm). In addition, the method of choosing waveforms at different depths of different pavement structures was provided, and the equation of calculating wavelength was recommended. Moreover, dynamic modulus under different loading waveforms were analysed through laboratory test, and the process for obtaining dynamic modulus of asphalt layer in any depth was presented.

Effect of carbon black on the dynamic moduli of asphalt mixtures and its master curves

Modulus is one of the main parameters during the design of asphalt pavement structure, the newest specifications of China gives the dynamic moduli ranges of commonly used asphalt mixtures with base asphalt (BA) or styrene-butadiene-styrene modified asphalt (SBS MA), while the moduli ranges of mixtures with carbon black modified asphalt (CB MA) are not recommended. To investigate the CB effect on the dynamic moduli of CB MA mixtures, one commonly used asphalt mixture (AC-20) was designed with BA, SBS MA, and CB MA, respectively. Then, the uniaxial compression dynamic modulus tests were conducted at different temperatures and loading frequencies, the master curves of asphalt mixtures were analyzed based on the time-temperature equivalence principle. The results show that with increasing loading frequency, the temperature dependence of dynamic moduli of all asphalt mixtures tend to be less obvious. Both SBS and CB can decrease the temperature sensitivity of asphalt mixture, the SBS MA mixture has the lowest temperature sensitivity, followed by CB MA and BA mixture. In addition, CB and SBS can obviously improve the dynamic modulus of the BA mixture, enhance the anti-deformation performance of pavement structure, and the improvement effect of CB is almost the same with SBS.

State of the practice in pavement structural design/analysis codes relevant to airfield pavement design

An airfield pavement structure is designed to support aircraft live loads for a specified pavement design life. Computer codes are available to assist the engineer in designing an airfield pavement structure. Pavement structural design is generally a function of five criteria: the pavement structural configuration, materials, the applied loading, ambient conditions, and how pavement failure is defined. The two typical types of pavement structures, rigid and flexible, provide load support in fundamentally different ways and develop different stress distributions at the pavement – base interface.Airfield pavement structural design is unique due to the large concentrated dynamic loads that a pavement structure endures to support aircraft movements. Aircraft live loads that accompany aircraft movements are characterized in terms of the load magnitude, load area (tire-pavement contact surface), aircraft speed, movement frequency, landing gear configuration, and wheel coverage.The typical methods used for pavement structural design can be categorized into three approaches: empirical methods, analytical (closed-form) solutions, and numerical (finite element analysis) approaches. This article examines computational approaches used for airfield pavement structural design to summarize the state-of-the-practice and to identify opportunities for future advancements. United States and non-U.S. airfield pavement structural codes are reviewed in this article considering their computational methodology and intrinsic qualities.

Evaluation of Clustered Traffic Inputs for Mechanistic-Empirical Pavement Design: Case Study in New Jersey

Truck traffic is one of the significant inputs in design and analysis of pavement structures. This paper focuses on comprehensive cluster analysis of truck traffic in New Jersey for implementation of mechanistic-empirical pavement design. Multiple year traffic data were collected from a large number of weigh-in-motion stations across New Jersey. Statistical analysis was first conducted to analyze directional and temporal (yearly) variations of traffic data. Hierarchical cluster analysis was conducted and three optimum clusters were found for axle load spectra (single, tandem, tridem), vehicle class distribution, and axle/truck ratio, respectively. Road functional classifications were employed to identify different clusters as no common geographic trend could be perceived. The results illustrate that the predicted performance using the site-specific traffic data is comparable with that using the traffic cluster for the selected 10 sites. Among four different traffic inputs, the cluster traffic inputs generated the closest predictions of pavement life as compared with those using site-specific traffic input and the default traffic inputs yielded the highest error. It is recommended to use traffic clusters in mechanistic-empirical pavement design when site-specific data is unavailable.

Shear Properties of Asphalt Mixtures under Triaxial Compression

In order to study the influences of confining pressure and temperature on the shear properties of asphalt mixtures, triaxial tests were conducted at 40 °C, 50 °C, and 60 °C, with the confining pressure ranges from 0 to 1 MPa for the widely used continuous-graded AC (Asphalt Concrete)-13, open-graded OGFC (Open-Graded Friction Course)-13, and gap-graded SMA (Stone Mastic Asphalt)-13 asphalt mixtures in China. A nonlinear regression/prediction model of triaxial strength for asphalt mixtures was proposed. The results show that confining pressure and temperature had a significant effect on the shear resistance of asphalt mixtures. With increasing temperature, the shear strength of the asphalt mixture gradually decreased due to the decreasing of cohesion strength; the shear strength of the asphalt mixture increased with the increase of confining pressure. Meanwhile, the cohesion strength increased and the friction angle decreased gradually with the increase of confining pressure. When the confining pressure was close to 0.6 MPa, the Mohr–Coulomb failure envelope bended down, so the linear Mohr–Coulomb criterion is not suitable to describe the failure behavior of asphalt mixtures. Therefore, a power function failure envelope was put forward to characterize the nonlinear shear properties of asphalt mixtures. The nonlinear evolutional laws of shear parameters, which includes cohesion strength and friction angle, were also proposed for asphalt pavement material and structure design. Among these asphalt mixtures, the gap-graded SMA-13 asphalt mixture exhibited better performance on the resistance to shear failure, and it was recommended as the upper layer material to improve the shear performance of asphalt pavement.

Bio materials with reclaimed asphalt: from lab mixes properties to non-damaged full scale monitoring and mechanical simulation

Three innovative environmentally friendly pavement materials, designed with 50% of Reclaimed Asphalt and three different biomaterials (2 bio-additivated bitumens and 1 bio-binder), were produced in an industrial plant. These mixes were tested in lab and also at full scale using an Accelerated Pavement Test facility. The asphalt mix viscoelastic properties were measured in lab and their intrinsic viscoelastic response were simulated. These rheological models are used to simulate the pavement mechanical response using both elastic and viscoelastic multilayer codes. Hence, full scale measurement performed during the full scale test at an early stage (without damages) can be compared with these simulations. The overall prediction accuracy, when all the signals are considered, is between 4% and 8% for all materials. It can be concluded that material characterisation in lab as well as the selected models are well adapted to simulate actual loading state under a moving load, even for these non-conventional mixes. For temperatures lower than 25°C, elastic modelling appears to be sufficient for pavement structural design with the innovative materials tested here.

Unified Strength Model of Asphalt Mixture under Various Loading Modes.

Although the rutting resistance, fatigue cracking, and the resistance to water and frost are important for the asphalt pavement, the strength of asphalt mixture is also an important factor for the asphalt mixture design. The strength of asphalt mixture is directly associated with the overall performance of asphalt mixture. As a top layer material of asphalt pavement, the strength of asphalt mixture plays an indispensable role in the top structural bearing layer. In the present design system, the strength of asphalt pavement is usually achieved via the laboratory tests. The stress states are usually different for the different laboratory approaches. Even at the same stress level, the laboratory strengths of asphalt mixture obtained are significantly different, which leads to misunderstanding of the asphalt mixtures used in asphalt pavement structure design. The arbitrariness of strength determinations affects the effectiveness of the asphalt pavement structure design in civil engineering. Therefore, in order to overcome the design deviation caused by the randomness of the laboratory strength of asphalt mixtures, in this study, the direct tension, indirect tension, and unconfined compression tests were implemented on the specimens under different loading rates. The strength model of asphalt mixture under different loading modes was established. The relationship between the strength ratio and loading rate of direct tension, indirect tension, and unconfined compression tests was adopted separately. Then, one unified strength model of asphalt mixture with different loading modes was established. The preliminary results show that the proposed unified strength model could be applied to improve the accurate degree of laboratory strength. The effectiveness of laboratory-based asphalt pavement structure design can therefore be promoted.

ANALISIS PERKERASAN LENTUR DI ATAS TANAH EKSPANSIF

The segmented road of Bireuen-Takengon has often damaged in apart of its pavement structure due to the area of flexible pavement structure taken place upon an expansive soil that leads to depreciation caused by the influence of changes in the water level. The aim of this research method was to analyze the characteristics of the base soil underlying the pavement and to analyze the flexible pavement structure in the widening of the road. The observed area was Sta.70+175 s/d Sta.74+925 which taken place in Bener Meriah regency, sub-district of Timang Gajah. The results of USCS clarification show that the road of basal soil is included in the MH and OH with a PI value of 25.42%, LL 64.25% with a potential level of development and activity belonging to the medium-high category and also having mineral types of Illite. From the analysis of KENPAVE software, the design of flexible pavement structures is based on data planning that has a maximum stress and deflection value, on the base soil, of 0.1814 kg/cm2 and 0.0585 cm respectively. Moreover, based on Job mix data the maximum value of stress and deflection is 0.2444 kg/cm2 and 0.0585 cm respectively in which both of two stress and deflections are within the allowable limit; which both of two stress and deflections are within the allowable limit; 7.8 kg/cm2 and 2.5 cm. The evaluation results of both data are feasible to be used as an improved design on the pavement as the pressure generated by the weight of the road pavement structure is 1.949 kg/cm2, while the swell pressure that occurs on subgrade is 1.805 kg/cm2. Hence, The flexible pavement structure on the road segment is still able to reduce the swell potential on expansive soil.

Partial-depth paved shoulder effect on part-time shoulder use pavement bearing capacity

In areas of high population density, widening all classifications of roadways for growing traffic volumes becomes increasingly complex and expensive to complete. For major highways in Europe and the United States (US), use of the shoulder as a part-time lane is becoming progressively common and may be a solution to growing traffic on lower roadway classifications. This approach is known as hard shoulder running internationally and part-time shoulder use (PTSU) in the US. For interstates or other major highways, the shoulder design is a full-depth paved shoulder, the same pavement cross-section as the mainline lanes, and is structurally sound. For arterials and collectors, the shoulder design commonly has a different pavement cross-section from the mainline lanes, a partial-depth paved shoulder design. This study focused on evaluating the design strength of typical partial-depth paved shoulder designs in the US for PTSU using the American Association of State Highway and Transportation Officials (AASHTO) Guidelines for Design of Pavement Structures 1993 design. The study sites were also redesigned according to the AASHTO design methodology to handle the PTSU design traffic volumes. This study found that two of the nine states evaluated could withstand PTSU with minor to no reconstruction.

Theoretical and practical methodology for recognizing the road surface structure

A recognition indicator of the possibility of further use of the road during transferring transport loads are changes in the condition of the road surface. If the surface condition indicates incorrect parameters of its equality, rutting, or cracks, the road durability is qualitatively assessed. In this case, the actual load capacity rating and possible reconstruction of the structure begins. Values of dynamic defl ections can be used to recognize the modulus of elasticity and thus the possibility of assessing the durability of a structure. The mechanistic method is used to dimensioning the structure due to the movement planned. It allows a fl exible approach to further construction, giving the opportunity to assess whether part or all of it should be left or apply an additional layer to meet future requirements. The elastic modulus needed for this pavement structure design method for existing layers has been recognized by identifi cation as backcalculation methodology that have been used for many years.

Development and Demonstration of Hot Mix Asphalt Design Guidance for Mix Performance-Related Specifications

As they adopt mechanistic-empirical (ME) methods for flexible pavement design, road agencies are starting to incorporate performance-related specifications (PRS) for hot mix asphalt materials to assure that the as-built materials meet the performance requirements assumed in the pavement structural design. PRS pose new challenges for materials producers and contractors who have never had to relate volumetric mix design parameters to performance requirements such as fatigue life and rutting resistance. The objective of this paper is to describe the development of guidance for materials producers and contractors to support their decision making with regard to changes to mix designs to meet PRS requirements. The guidance was first developed based on known experience. To validate the guidance and demonstrate its usage, a production mix meeting Superpave volumetric requirements for California state highways was selected as the starting point for a set of adjustments applied to the mix. The effects of each adjustment were evaluated by conducting laboratory tests to determine mechanistic performance parameters used in structural design. The mechanistic performance parameters evaluated in this study include stiffness, fatigue resistance, and rutting resistance. The initial experience-based mix design guidance was found to be generally consistent with the laboratory test results for the example mix, albeit with some minor exceptions. The mix design guidance was then revised based on findings from this study. It is recommended that the revised guidance be used as non-mandatory advisory information for projects with PRS and that it be further improved with more results.