Repeated Wheel Loading Research Articles

Pavement performance and model studies with modified bitumen binder

Flexible pavements experience premature deterioration due to several factors, such as high volumes of traffic, repeated wheel loads, overloading, adverse weather conditions, inferior quality of materials, and other related issues. One of the most commonly found types of distress is rutting, which severely affects pavement performance; hence, the prediction of rutting behaviour is crucial. Research has been done by adding various industrial wastes, chemicals, additives, and modifiers such as rubber, natural rubber, polymers, and waste plastic into the bitumen. These materials are expected to have a substantial impact on enhancing the strength, durability, and performance of pavement while simultaneously reducing the cost of construction. The present research deals with a laboratory investigation of bituminous mixes using both Marshall stability and rutting tests. The performance tests were carried out by Roller Compactor cum Rut Analyzer (RCRA) equipment and Finite Element (FE) analysis in ABAQUS. The experimental findings show that the modified bitumen exhibits 48% greater strength and 20% more resistance to rutting than the conventional bituminous mixes. The model analysis was successfully validated by experimental results. The findings of the research resulted in the development of a mathematical equation that helps to calculate in-service pavement rut depth.

Improving skid-resistance durability of ultra-thin friction course in asphalt pavements through recycled steel slags as basalt replacements

The ultra-thin friction course (UTFC) has emerged as an effective solution for restoring skid-resistance on worn pavements. However, the scarcity and high cost of high-quality basalt aggregates pose challenges for UTFC implementation. This study explores the potential of utilizing recycled steel slags (blast furnace slag (BFS), basic oxygen furnace slag (BOFS), and electric arc furnace slag (EAFS) as alternatives to basalt aggregates in UTFC applications. The durability of skid-resistance and shear strength of these steel slag-UTFCs are investigated, and the chemical and mineral compositions of the steel slags are analyzed to assess their suitability. The findings reveal that EAFS-UTFC exhibits superior surface roughness, enhanced wear resistance, and comparable shear strength to Basalt-UTFC. The dynamic friction coefficient (μ) between EAF-UTFC and rubber at 120 km/h is 1.12 times higher than that of basalt at 0 wear cycles, and this advantage amplifies to 3.11 times higher after 400k wear cycles. However, BFS and BOFS are not suitable for direct use in UTFC, which have lower wear resistances and shear strengths compared to basalt, attributed to their poor bulk stability caused by high levels of free CaO and MgO. Consequently, a significant portion of their surface aggregates are dislodged under repeated wheel loading before sufficient polishing occurs. This study offers insights into sustainable solutions for improving skid-resistance on asphalt pavements.

Rutting Prediction of Asphalt Mixtures Containing Treated and Untreated Recycled Concrete Aggregate

Rutting is a crucial element of the mechanical performance characteristics of asphalt mixtures, which was the primary target of this study. The task involved substituting various portions of virgin coarse aggregate with recycled concrete aggregate materials that had been treated or left untreated at rates ranging from 25 to 100%, with a constant increase of 25%. The treatment process of recycled concrete aggregate involved soaking in acetic acid, followed by a mechanical process for a short time inside a Los Angeles machine without the balls. This research utilized two primary tests: the standard Marshall test to identify the optimal asphalt contents and the volumetric characteristics of asphalt mixtures. The other one was the wheel tracking test, which involved manufacturing 11 slabs with a dimension of 30 x 40 × 5 cm and testing them under repeated wheel loads of 700 N at 55°C to investigate rutting resistance. The results demonstrate that using RCA had a negative impact on rutting resistance, where rut depth increased by 21.64% when using 100% pre-soaked treated RCA.

Behavior of Bamboo and Jute Geocell Overlaying Soft Subgrade under Repeated Wheel Loading

Behavior of Bamboo and Jute Geocell Overlaying Soft Subgrade under Repeated Wheel Loading

Numerical Investigation of Residual Stress Formation Mechanisms in Flash-Butt Welded Rail

For the construction of long and continuous railway lines as well as the replacement of defected rails, rails are joined using flash-butt welding. Under various localized temperatures and thermo-mechanical stresses, a residual stress can develop in the flash-butt welded joint. The residual stress can affect the performance and reliability of the welded rail, particularly in terms of progressive structural damage caused by repeated wheel load. In the present work, the mechanisms of residual stress formation in a flash-butt welded rail and the influence of upsetting force (including its temperature range and magnitude) were investigated using the thermal elastic–plastic finite element analysis. The formation mechanisms of residual stress involved the changes in thermal expansion coefficient, strain, and elastic modulus of the welded joint with respect to temperature. The calculated cooling temperatures and residual stresses in the flash-butt welded joint were in good agreement with the measured results. Compressive residual stresses were observed around the rail head and the rail foot (i.e., approximately −648 MPa at the rail head and −495 MPa at the rail foot), while tensile residual stresses were observed at the rail web (i.e., approximately 165 MPa). It was observed that the investigated compressive upsetting force predominantly induced plastic deformation within the welded joint, resulting in minimal alteration of stress. Consequently, the investigated ranges of upsetting temperature and upsetting forces had an insignificant impact on the formation of residual stress.

Study on Comparision of Life Cycle Cost Between White Topping and Btiuminuos Overlays

Abstract: The focus of the present study is on construction of long-lasting and better performing pavements. Usually, with respect to the rehabilitation of the pavement, the construction agencies go with the bituminous overlays as their first priority without considering the condition of the existing pavement structure. But the advantages of cement concrete (CC) pavements that have proved to perform better and are considered to be long-lasting must be explored. The use of Thin White Topping (TWT), and Ultra-Thin White Topping (UTWT) pavements is currently gaining popularity in the area of pavement construction.. And hence it is the era where the Thin and Ultra-Thin White Topping methods are gaining their popularity. The present study provides details on the approaches adopted in measuring the performance of TWT and UTWT pavement surfaces built of plain cement concrete, cement in cement concrete replaced by 50% ground granulated blast furnace slag, cement in cement concrete replaced by an admixture called Conplast NC, and 50% of cement in cement concrete replaced by GGBS and Conplast NC. The study also includes comparison of strength of composite beams of various thicknesses when subjected to repeated wheel loads under Modified Immersion Wheel Tracking Equipment when supported by a 50mm thick bituminous layer below. The performance results on the tests on the specimens of 150mm thick admixture-added CC beam and the 100mm thick GGBS-cumAdmixture-added CC beam were almost the same. This indicated that the thickness of cement concrete slabs could be reduced by 50mm by replacing 50% of cement in cement concrete with GGBS-cum Admixture-added CC beam. Based on the study on cement concrete, and composite beams, and the study of life cycle costs, it was observed that a road surface with cement concrete overlay would be more appropriate when compared to a bituminous concrete (BC) overlay. Together, these findings suggest that the concrete overlay acts as the most economic method.

Testing and evaluation for long-term skid resistance of asphalt pavement composite seal using texture characteristics

As a common means to improve the skid resistance of asphalt pavement, chip seal is widely used for road surface treatment and preventive maintenance. As the aggregate is progressively dislodged under repeated wheel loads, continuous loss of the surface texture characteristics occurs, and its skid resistance increasingly declines. Therefore, it is necessary to further refine the process of chip seal. In addition, in order to scientifically evaluate its performance and accurately predict the deterioration, the relationship between the surface texture characteristics and the skid resistance needs to be quantitatively established. In this paper, a composite seal structure was proposed by applying sand-containing fog seal layer on top of chip seal. Firstly, four seal schemes (i.e., 3–5 mm chip seal, 5–9.5 mm chip seal, 3–5 mm composite seal and 5–9.5 mm composite seal) were designed and loaded by a four-wheel rotary accelerated abrader. Secondly, the skid resistance indexes of each scheme were investigated under different abrasion times using pendulum meter and sand patch method. In this process, the three-dimensional texture characteristic parameters (i.e., Ssk, Spd, Spc, Vmp and Vmc) of the specimen surface were also obtained by laser scanning. Finally, by analyzing the data, the relationship between the seal texture characteristic parameter and the skid resistance index was established, and the decay law prediction model of the skid resistance for four seal schemes was derived. It is found that the pendulum value and texture depth of the seal decreased with the increase of abrasion times, but the composite chip seal can reduce the decreasing rate of skid resistance index. Sq, Spd, Spc and Vmc showed good synergistic decay laws with the British pendulum number (BPN) and mean texture depth (MTD), among which Spc had the best correlation and can be used as an parameter to characterize the skid resistance of the seal. The relationship and decay prediction model established in this paper can be used to characterize the skid resistance of chip seal and predict the decay law of the skid resistance.

A 3D-FE Model for the Rutting Prediction in Geogrid Reinforced Flexible Pavements

Permanent deformation (rutting) is an important disturbing failure on flexible road pavements. This phenomenon appears on the flexible pavement as longitudinal depressions, and it is a consequence of the degradation of materials under high traffic loading based on consolidation/densification, surface wear, plastic/shear flow, and mechanical deformation. Hence, the rutting phenomenon depends on the accumulation of permanent deformations on pavement surfaces subjected to repeated wheel loads. In recent years, several studies have confirmed that the service life of asphalt pavements can be increased by using geosynthetics between or within layers because of the improved mechanical properties. The aim of this paper is to present the results of the 3D-finite element (FE) simulations and the development of the rutting phenomenon in a traditional flexible pavement and a reinforced one, both subjected to a cyclic load. Through Abaqus/CAE software, a road section reinforced by a geogrid was analyzed and compared with a traditional road section to investigate the advantages given by the geosynthetic completely embedded at two-thirds of the asphalt concrete layer (AC) in terms of permanent deformations. The results show the capability of the proposed FE study, that uses the plasticity model of Drucker-Prager for unbound materials combined with the simple creep law to model HMA layers to predict the permanent deformation distribution.

Fatigue life analysis of wheel-rail contacts at railway turnouts using finite element modelling approach.

The article deals with wheel-rail contact analysis at railway turnout using a finite element modelling approach. The focus is understanding the wheel-rail contact problems and finding the means of reducing these problems at railway turnouts. The main aim of the work reported in this article is to analyse fatigue life and simulate the wheel-rail contact problems for a repeated wheel loading cycle by considering the effect of normal and tangential contact force impact under different vehicle loading conditions. The study investigates the impact of tangential contact force generated due to different-angled shapes of the turnout and aims to reveal how it affects the life of contacting surfaces. The obtained results show that the maximum von-Mises equivalent alternating stress, maximal fatigue sensitivity, and maximum hysteresis loop stresses were observed under tangential contact force. These maximum stresses and hysteresis loops are responsible for rolling contact fatigue damage, and excessive deformation of the wheel-rail contact surface. At a constant rotational velocity, the tangential contact force has a significant impact on the fatigue life cycle and wheel-rail material subjected to fatigue damage at lower cycles compared to the normal contact force. The finite element modelling analysis result indicated that the contact damages and structural integrity of the wheel-rail contact surface are highly dependent on contact force type and can be affected by the track geometry parameters.

A mechanistic approach to evaluate the fatigue life of inverted pavements

Fatigue cracking is one of the most critical failure types in flexible pavements under the application of repeated wheel loads. The application of vehicular load induces micro-cracks with each application eventually causing macro-cracks and failure. The chances of crack propagation multiply if a brittle cement-treated base layer lies underneath, as in the case of an inverted pavement. This study investigates the fatigue cracking in inverted pavements considering the effect of the brittleness of an underlying cemented layer. Several specimens were manufactured and tested in a wheel tracking environment while crack initiation and propagation were carefully monitored using a GoPro camera. A mechanics-based methodology has been developed to calculate the critical horizontal tensile strain at the bottom of the hot mix asphalt surface layer, which has been related to fatigue life by a fatigue prediction model. It is observed that the laboratory results are in close correlation with the predicted fatigue life. The developed approach has also been successfully applied to real pavements, constituting an important development in fatigue life prediction in inverted pavements.

Experimental Study on Mechanical Behavior of Lean Cemented Sand and Gravel Material in Unloading and Reloading Paths

Lean cemented sand and gravel (LCSG) materials are subjected to unloading‐loading when an LCSG dam is opened for water drainage and then refilled or a roadbed base is subjected to repeated wheel loads. To investigate the behavior of the LCSG materials under loading‐unloading, previous studies utilized the complete loading triaxial test. In contrast, in this study, the consolidated drained triaxial tests in the unloading and reloading paths for materials with cementing agent contents of 60 and 100 kg/m3 under different confining pressures, for which each curve generates three loading‐unloading cycles, were applied to investigate the unloading and reloading mechanical behavior. Experimental results indicated that the unloading and reloading behavior of the LCSG materials produced stress‐strain curves exhibiting a crescent‐shaped hysteresis loop, which differs from that exhibited by coarse‐grained soil. Although the shape of the crescent‐like hysteresis loop was preserved as stress levels increasing, it gradually expanded. Compared with that of the typical triaxial test, the cohesive force and the increasing internal friction angle increased. Further, as the confining pressure increased, the crescent‐like hysteresis loops tapered, shear strength increased linearly, and the modulus of resilience increased nonlinearly; the latter’s rate of change, however, decreased. The change in volumetric strain was small during unloading as the stress level changed.

Organization of autonomous truck platoon considering energy saving and pavement fatigue

Autonomous truck platoons are currently proposed to drive in an aligned form for saving fuel, which will cause repeated wheel loads and shorten pavements’ service life. Therefore, platoon’s form needs to be reconsidered. Several forms were proposed from the aspects of vehicle number, longitudinal interval and lateral offset. Their influence was evaluated based on the computational fluid dynamics simulations and finite element model. Parameters in the simulations were collected from laboratory tests. The average fuel-saving rate for a two-truck platoon is 3.8–8.9% when the longitudinal interval varies from 5L to 0.5L. The fuel-saving rate, however, grows at a decreasing rate with the increase in truck number. Besides, the lateral offset is found to be effective when organizing the two-truck platoon, and above 30% decrease in pavement fatigue damage and 8% fuel savings will be obtained concurrently. The findings help the policy makers to reconsider the management of platoons.

Performance Studies on white topping layers over flexible pavement

The main focus of the present era is to construct a long-lasting and better performing pavement. Usually, with respect to the rehabilitation of the pavement, the construction agencies go with the bituminous overlays as their first priority without considering the condition of the existing pavement structure. But CC pavements have proved that they perform better and are long-lasting as new pavement as well as when used for rehabilitation of the existing pavement. And hence it is the era where the Thin and Ultra-Thin White Topping methods are gaining their popularity. Hence in this study, in order to arrive at the performance of the TWT and UTWT methods, various types of basic and the performance tests have been carried out with different combinations of concrete i). Plain Cement Concrete ii). Cement replaced by Ground Granulated Blast furnace Slag (GGBS) (50%) iii). With admixture (Conplast NC) iv) 50% Ground Granulated Blast Furnace Slag GGBS + Conplast NC. Later to understand the performance of these combinations, the composite beams with varying thickness are subjected to repeated wheel loads under Modified Immersion Wheel Tracking Equipment along with a bituminous layer of 50mm thick below the cement concrete layer. The performance results of 150mm thick admixture added CC beam and the 100mm thick GGBS & Admixture added CC beam has almost the same value. Hence, it can be concluded that the slab thickness can be reduced by 50mm by replacing 50% GGBS to the Admixture added CC beam.

Development of fatigue damage model of asphalt mixtures based on small-scale accelerated pavement test

As the primary surface type for high-grade Chinese highways, the long-term performance of asphalt pavement can affect significantly transportation efficiency. It has been confirmed that fatigue cracking is one of the major failure modes for asphalt pavement, which can cause a great reduction of asphalt pavement durability. Currently, the fatigue properties of asphalt mixtures are evaluated mainly based on traditional laboratory fatigue tests, such as bending fatigue tests and indirect tensile fatigue tests. However, none of these fatigue test methods can realistically evaluate the fatigue performance of asphalt pavement under the repeated wheel load. To resolve this issue, the model mobile load simulator (MMLS3), which is a small-scale accelerated pavement test device, was utilized to evaluate the fatigue life of six kinds of asphalt mixtures. The fatigue damage variable was defined as stiffness reduction. Based on the small-scale accelerated pavement test, a stiffness reduction model for asphalt mixtures was determined. A stiffness reduction law for asphalt mixtures during the fatigue process was proposed. The stiffness evolution process could be divided into three phases, which are the adaptation phase, the quasi-stationary phase, and the failure phase. A maximum value of the rate of stiffness reduction from the quasi-stationary phase into the failure phase was proposed as the failure threshold. Besides the fatigue life obtained from the failure criteria had a good agreement with the test results. The results from this research can be used as a theoretical reference for evaluating the fatigue life of asphalt mixtures and improving the durability of asphalt pavement.

Study on the effect of residual stresses on fatigue crack initiation in rails

Rolling contact fatigue cracks shorten rail service life, and increase costs of rail maintenance and replacement significantly. The aim of the present study is to investigate the effect of residual stresses induced by manufacturing and repeated wheel-rail contact on fatigue crack initiation in rails. To this end, three-dimensional finite element models of rail on-line heat treatment, rail straightening, and wheel-rail contact were established to study the state of residual stresses of on-line heat-treated rails. The effect of residual stresses induced by rail manufacturing and repeated wheel-rail contact on fatigue crack initiation was analyzed based on a fatigue parameter FPmax by Jiang–Sehitoglu low cycle fatigue criterion. Rail fatigue crack initiation mechanism under the combined action of wheel load and residual stresses was studied. The results show that residual stresses induced by rail manufacturing affect the stress state of on-line heat-treated rails after repeated wheel loads. The influence of residual stresses induced by rail manufacturing and repeated wheel-rail contact on the FPmax of rails is significant. However, there is no positive or negative correlation between residual stresses and FPmax of rails under different wheel loads and friction coefficients.

Subsurface deformation mechanisms beneath a flexible pavement using image correlation

Flexible pavement structures are widely used in road construction, especially in circumstances where very high traffic volumes are not expected. These structures comprise multiple layers of granular material, which generally have decreasing strength with depth. Failure of these systems is typically observed as rutting on the ground surface, but the failure instigates at depth. In this research, for the first time, observations can be directly made of the progressive failure of these deeper layers under repeated wheel loading due to the combination of a new test apparatus, the Cambridge accelerated pavement tester (APT) and digital image correlation (DIC) technology. The use of a window allowing observation of soil displacements at depth during repeated wheel loading cycles allows the progressive failure to be observed and the changes in soil displacements and strains with different layer thicknesses to be quantified. It was observed that the critical failure mechanisms for thin and thick surficial layers are different, resulting in changes in the rates of surface rutting. Understanding these deformation mechanisms potentially allows savings to be made in road or airfield construction by using correctly sized structural layers.

Pervious concrete under flexural fatigue loading: Performance evaluation and model development

Pervious concrete (PC) is used for parking lots and streets that are subjected to repeated wheel loading, therefore it is necessary to characterize the fatigue life (N) of PC for pavement design. This research investigates the behavior of PC beams made with two aggregates (angular and round) and three porosity levels (20%, 25% and 30%) under flexural fatigue loading in three stress ratios (SR:) 0.75, 0.8, and 0.85. The results showed that N is controlled by SR, while porosity showed no statistically significant effect on flexural fatigue. Two-parameter Weibull distribution was fitted to the test data to generate fatigue models at different reliability levels. Using the existing model for portland cement concrete (PCC) for PC results in an overestimation of N for SR > 0.75 due to the highly porous and brittle macrostructure of PC. Existing PCC model agrees with the proposed PC model in predicting N at 0.5 < SR < 0.75, while overestimates N at SR < 0.5. The proposed fatigue model can be used in the thickness design of PC pavements.

A prototype fatigue test for slab track subjected to the coupling action of wheel load, temperature variation, and water erosion

Slab track is commonly used for high-speed railways in China. During its service life, the performance of the slab track may be affected by repeated wheel loading, temperature variation, and water erosion. In this study, a prototype fatigue test for the slab track was carried out during the winter season in a severely cold region of northeast China, considering the coupled effects of wheel load, temperature change, and water erosion. A loading vehicle configured with eccentric vibrator wheels was used to apply repeated wheel loading. The slab track system was heated and/or cooled to produce a temperature gradient consistent with the statistical characteristics of a real track system. Water erosion was also applied. The results show that the fatigue damage to the main structure of the slab track was less, even after 18.7 million cycles of wheel load under a severe temperature gradient. However, the cement asphalt mortar under the track slab may deteriorate rapidly from the edge and corner of the track slab when some initial damage was already present.

Preliminary Investigation of Predicting Permanent Deformations of Unbound Granular Materials Using Miniaturized Pressuremeter Cyclic Data

Abstract The permanent deformations of unbound pavement layers are typically caused by the movement and densification of aggregate particles under the influence of repeated wheel loads. This type of distress, which represents one of the major failure modes in flexible pavements, has been investigated by many researchers. In this research, a miniaturized pressuremeter (MPMT) device was used to predict rutting of unbound granular materials by performing cyclic field testing. The permanent deformations measured using cyclic triaxial (CT) testing were compared with those predicted from the MPMT testing. Four unbound pavement materials used as a pavement base and subgrade were tested and evaluated. The Tseng-Lytton model, also known as the sigmoidal model, was used to analyze and interpret permanent strain data obtained from both tests. The data showed that the permanent strains predicted from in situ MPMT tests are larger than those measured from laboratory CT tests. However, it is demonstrated that the best results are obtained when MPMT permanent strains are adjusted by using the slope of the strain level model as a reduction factor. The results indicated that the average ratio of predicted to measured permanent strain was 0.66 and 0.89 for subgrade and base course materials, respectively. In addition, it was concluded that the MPMT stress-strain data from ten MPMT loading cycles provide a reasonable estimation for soil strain parameters of the sigmoidal model.

Determination of Stone-Mastic Asphalt Concrete Durability

The paper is focused on determination of durability of the stone-mastic asphalt (SMA) concrete, containing various stabilizing additives: "Armidon" (authors’ development) and "Viatop". At the first stage of experiments, the APA method was used to determine the rutting in the SMA containing these additives. Strength test for only top layers of asphalt concrete surface is insufficient for the calculation of the pavement fatigue resistance limits. Due to this fact, a comprehensive approach was employed which incorporates the interaction of the surface and subgrade natural soil. To analyze the road surface stress-strain state and to determine the durability margin, a numerical model was used (describes the processes of fatigue life). The model was developed basing on the finite element method (FEM) in the ANSYS program. Conducted studies and numerical calculations allowed obtaining the minimum and maximum stress values in the structure affected zones and in the zones of plastic deformations occurrence in artificial and natural bases. It allows predicting deformation processes during repeated wheel loads caused by moving vehicles. In course of studies, the results of static stresses in the pavement were also obtained.