Using Surface Deflection for Detection of Interface Damage Between Pavement Layers

A critical aspect of designing road pavements is accurately estimating the expected traffic load. It's important to note that not all vehicles use the same wheel path when traveling on a road. Many factors, including the Lane Distribution Factor (LDF), can affect the lateral shift of the load applied to the pavement. LDF is a crucial factor in designing flexible pavements, as it helps transportation planners and highway engineers estimate lane usage relative to the total traffic volume. This information is essential for understanding how pavements respond to wheel loads and fatigue behavior. The IRC: 37 - 2018 guidelines provide a set of LDFs for estimating the design traffic in terms of Million Standard Axle Loads. However, to ensure the accuracy of these LDFs, a study was conducted on rural and urban highways with two and four lanes to identify the lateral distribution of the vehicles.

Economic Analysis of Pavement Layers According to AASHTO-86 Method In AASHTO-86 design method, the structural number (SN) is determined in respect of bearing capacity of subgrade, total standard equivalent axle load, reliability level, standard deviation and serviceability index because of the structural number have to be equal and bigger than the sum of the coefficient that is multiplied with layer thickness and drainage factor a lot of combination occurs. In this study 441000 alternative occurred from the different values of parameter placed in design criterion have been analyzed according to AASHTO-86 method by using MATLAB program. In conclusion the economic thickness of layers forming pavement for different equivalent axle load number, the effect of the bearing capacity of subgrade on pavement cost, the mathematical relation between axle load number, bearing capacity and cost of pavement and the most suitable and economic base and subbase type have been determined.

This paper presents the average truck equivalency factors for four types of full-trailer trucks on uphill flexible pavements. Rising grades of 6%,12% and 18% are considered in addition to level flexible pavements. To arrive at each truck equivalency factor for the 254 full-trailer trucks studied, the axle loads were obtained from an axle load survey using permanent weighing stations. Assuming uniform motion, the axle loads on uphill pavement were calculated for different relative height of the centre of gravity of truck above pavement taking into consideration the pull force in the hook connecting both units of each full-trailer truck. The effects on average truck equivalency factor of uphill gradient, type of full-trailer truck, relative height of centre of gravity of truck, pavement structural number and terminal level of serviceability, were thoroughly studied. The paper reveals that an increase in uphill slope causes a significant increase in flexible pavement thickness especially for steep rising grades in developing countries. For rough estimation of standard single axle load applications on uphill pavements from level pavements, overall average uphill slope factors were developed. The uphill slope factor of unity for level pavement increases by about 0.038 per each 1% increase in uphill slope.

Undertaken in the field of design methods for flexible pavement, the present study focuses on the introduction of traffic loads, applied mainly to mechanistic empirical methods. In such research, strains due to traffic loads — calculated by pavement modeling based on linear elastic theory — are used for the evaluation of the life duration of the pavement. Real traffic loads on pavement vary significantly according to their intensity as well as their application modes. Our work aims to evaluate the relevance of the simplifying assumptions used in modeling to determine which parameters used in the description of traffic loads have more influence on the strains in flexible pavements. The study is chiefly based on experimental data. Strain measurements were made on several road structures, varying the main parameters of traffic loads, i.e. load intensity, inflation pressure of the tires and type of wheels. These measurements were carried out at various temperatures. Two structures featuring contrasted rigidities were modeled according to the French design method for flexible pavement. The horizontal strains exerted on these structures were studied at two depths : the bottom of the base course and the bottom of the wearing course. Then, experimental data were systematically compared with the modeling results. Strains at the bottom of the base course were both analyzed related to their maximal value — which corresponds to one of the design criteria used in mechanistic empirical methods — and as signals corresponding to the strain recordings in one given point during the passage of a traffic load. Analysis of maximal values allowed an evaluation of the influence of the studied load parameters and lead on to solutions to include them in calculations for equivalent traffic. The study of strain signals resulted in the definition of values allowing to express strain variations in function of time. The said values apply principally to notions like strain rates and the definition of frequencies that will best model strain variation in time with a sinusoidal curve. Such frequencies are obtained by decompositions in Fourier series. A relation between load speed and frequency has been defined. At the bottom of the wearing course, the study focused on strain signals only, with strange variations — which have been called — appearing in the horizontal strains at low depth. The scrutiny of these irregularities showed that bituminous materials located near to the road surface of flexible pavements are paradoxically more stressed horizontally than vertically. A situation that tends to link the behavior of bituminous layers in flexible pavements to the performance of a slam structure. Analysis of strain signals was supplemented by linear viscoelastic modeling based on Huet's model. If introducing the viscoelastic behavior of the bituminous layers showed no notable improvement in the quality of modeling, it nevertheless highlighted the necessity to model the pavement structure as a whole. Stress analysis underlined the effects of interactions between layers following different patterns of behavior and the importance of the interface conditions between these layers. Finally, the influence of the real vertical load pressure distribution on stress and strain in bituminous layers has been evaluated with elastic modeling. Variation of the loading conditions showed little effects on stress and strain distribution in the bituminous layers.

The nonlinear behavior of soils and granular materials is widely known. Its proper evaluation is essential for the accurate determination of the stiffness of pavement layers and their structural evaluation. If this phenomenon is not considered appropriately, it can lead to significant errors in estimating the pavement responses. As part of the investigation of accelerated tests on full-scale pavements by the National Laboratory of Materials and Structural Models of the University of Costa Rica, four instrumented pavement sections were built and evaluated using a Heavy Vehicle Simulator. The wheel load was used at an average speed of 10 km/h, with various loading levels, at an average temperature of 23 °C and with a lateral wandering of 10 cm. The deflection profile of each pavement was studied by means of Multi-Depth Deflectometer sensors (MDDs), the Road Surface Deflectometer (RSD), and; the Falling Weight Deflectometer (FWD). This paper summarizes a comparison among the differences in the deflection basin measurements, and the related estimated moduli. Additionally, the pavement response modeling was performed by means of Multi-layer Elastic (MLE), Finite Element (FE) and Linear Visco-Elastic (LVE) methods. The objective of this study was to compare the results of different deflection measuring methods and their correspondent backcalculated moduli. The analysis showed similar results in the deflection curves and hence, back-calculated moduli obtained by the MDDs and the RSD. Both devices captured, as expected, nonlinear behavior of the granular materials as well as the subgrade. The FWD was not able to report such behavior.

The use of synthetic and natural fibers in composite materials has been proven to increase strength and reduce required amounts of basic building materials. Previous research has determined that fibers have a high tensile strength and the potential to increase the cohesive and tensile strengths of asphalt mixtures. Additionally, previous research suggests that skid resistance is influenced by changes in the asphalt penetration grade. Short decorticated and pulp coconut fibers were used as additives in this study. Short coconut fibers measuring 0.5-1.25 cm were mixed with pen 60/70 asphalt to yield fiber contents of 0%, 0.75% and 1.5%. The fibrous asphalt was mixed with asphalt-concrete-wearing-course-grade aggregate. The asphalt concrete mixture was molded and compacted with a wheel tracking compactor using an 8.16-ton standard vehicle axle load. Specimens were subsequently tested with a British pendulum tester at temperatures of 26 oC, 30 °C, 35 °C, 40 °C, 45 °C, and 50 °C. Skid resistance decreased with an increase in pavement surface temperature. The inclusion of 0.75% coconut fiber in the asphalt mixture improved skid resistance but did not improve resistance to increased road surface temperatures.

In Ethiopia the failure of roads are before handover period. Most roads found in Ethiopia are flexible pavements. Nowadays, the failure of surface of flexible pavement roads are common before the expected design period. For the example Bako-Nekemte road/ has become a critical issue in our country. The most common parameters that cause stress, strain and deflection of the roads are loads and pressures that come from vehicles. Moreover, modulus of elasticity, Poisson’s ratio and thickness of each layer needs to be characterized. Further, the load magnitude, contact pressure (or load radius) and location are defined for each load (wheel) considered. Finite element method (FEM) is a numerical analysis technique to obtain the stress-strain and deflection of each pavement layers. Analytical method usually uses layers thickness, loads, elastic modulus and Poisson’s ratio of the pavement materials as design parameters. The objective of this research was to study the sensitivity of the road parameters in analyzing the major causes of failure in asphalt pavement layers fatigue cracking and rutting deformation which came due to the critical tensile strains at the bottom of the asphalt layer and the critical compressive strains on the top of subgrade using the finite element method by relating the standard specification of ERA and laboratory test result. This thesis studied the analysis of stress-strain and deflection of flexible pavements using Everstress finite element method. The Ever stress program will take into account any stress dependent stiffness characteristics. This thesis dealt with ways to reduce deflections by varying the design configuration, such as increasing the HMA modulus, the base modulus, sub base modulus, the subgrade modulus and increasing thickness of each layers. Based on type of materials to use the value of elastic modulus and poison’s ratio are various in each layers, in layer 1 is varied from 1500 to 3500 MPa, in layer 2 is varied from 200 to 1000MPa, in layer 3 is varied from 100 to 250 MPa and in layer 4 is varied from 20MPa to 150MPa.

Pavement distress is the condition of the pavement structure that impairs or contributes to the impairment of serviceability. Stress from axle loads, temperature change in bituminous layer, and moisture and temperature fluctuations in an underlying layer can all contribute to this condition. Nevertheless, pavement response under moving loads behaves as a time-dependent and transient parameter, and as axle loading and speed requirements have continued to increase due to an increase in traffic volume, an improved model for evaluating stresses and deflections of pavement has become a pressing need. Multiple nonlinear layers sitting on a foundation containing the interaction of numerous variables compose the pavement structure. Consequently, numerous academics have taken a rational approach to finite element (FE) modelling for improved pavement simulation and analysis. In addition, it is widely acknowledged that, due to the complexity of vehicle and pavement modelling when addressing the influence stress from axle loads, numerical methods of analysis is required. Since one hundred years ago, asphalt-coated flexible pavements and roadways have been in use. Currently, flexible pavements are primarily designed using empirical methods. However, a trend toward more mechanistic design methodologies is currently occurring. In general, layered elastic analysis and twodimensional finite element (FE) approaches have been used to predict stresses, strains, and displacements in flexible pavements; nevertheless, they suffer from a number of significant drawbacks. To address these issues, pavement constructions must be analyzed using three-dimensional (3D) FE analysis. This study examines the usage of ANSYS and KENPAVE to analyses the reaction of the distress model of flexible pavements using Finite-Element Methods

Concrete and composite (asphalt over concrete) pavement distress frequently occurs in the vicinity of joints or cracks in the concrete slabs. Water can enter into the pavement structure at these locations, leading to concrete deterioration and loss of subgrade support. Permanently patching these weakened areas can extend the pavement life considerably before major rehabilitation or reconstruction becomes necessary. Identifying where these or other distresses are occurring in composite pavements is problematic, however, because the asphalt overlay masks the defects in the underlying concrete. Reflective cracking in the overlay can indicate the presence of the joints or working cracks in the concrete, but the visual appearance of the surface is not a reliable indication of the soundness of the concrete. So, accurately identifying where to patch and how long patches should be is extremely difficult. The preferred method for repairing these pavements in Indiana and many other states is through the use of full-depth doweled concrete patches with asphalt overlay. In many cases, matching the existing pavement in terms of foundation and pavement materials and layer thicknesses is called for. This can create logistical and construction problems because of the need to perform different types of work with different materials and equipment, often with restricted times for lane closures. This research was undertaken in an attempt to identify best practices used by other states and documented in the literature to improve the identification, construction and performance of patches in composite pavements through a literature review and survey.

Comparative analysis of strain-pulse-based loading frequencies for three types of asphalt pavements via field tests with moving truck axle loading

The accelerations of sandwich-type composite pavements consisting of cross-tensioned concrete pavement (CTCP), asphalt sand (AS) stress-absorbing layer, and continuously reinforced concrete pavement (CRCP) layers from the top to the bottom were measured under different traffic loads. First, the acceleration spectra of double plates of composite pavements were measured under axle loads of 100, 200, and 300 kN using an embedded accelerometer. The universal mean of the acceleration ratio of CTCP to CRCP was defined as the stress-absorbing ratio of the AS layer as obtained through statistical analysis of the test data. A frequency spectrum was obtained for the pavement under each vehicle load by using Fourier transformation. Test results show that the maximum acceleration of CTCP and CRCP in composite pavements was 0.022, 0.039, and 0.059 ms−2 and 0.01, 0.015, and 0.025 ms−2 under vehicle loads of 100, 200, and 300 kN, respectively. The corresponding mean stress-absorbing ratio of the AS layers was 3.38, 3.15, and 3.46. The results suggest that the proposed composite pavement is suitable for roads with heavy traffic because its stress-absorbing layer can effectively reduce the pounding caused by heavy loads on the pavement.

Recent research in the USA has focused on the design, construction and performance of composite concrete pavements – that is, two heterogeneous concrete layers placed sequentially using ‘wet-on-wet’ techniques. In addition, other research into rehabilitation practices has focused on improving the design and analysis of bonded concrete overlays of concrete pavements and bridge decks. While these techniques can offer many benefits to pavements and bridges, they also introduce some uncertainties, including the possibility of thermally, hygrally, or mechanically induced fracture and separation at the interface of the concrete layers. In this work, the potential for mixed-mode fracture at the interface between concrete layers is evaluated using three-dimensional lattice models. This discrete approach is coupled with a finite element model for plate behaviour away from the potential cracking zone. The model, using two damage criteria, was verified and validated against experimental data for failure in notched concrete beams in three-point testing. In addition, simulations were conducted using each criterion for interface failure in a composite concrete pavement. The simulation results suggest that interface fracture is unlikely, even when considering unfavourable conditions such as substandard material properties and large temperature differences between the pavement layers.

Flexible pavements become significant structural elements, which are really vulnerable to the probable damage resulting from various traffic loads and an aggressive environment. In order to bolster the structural strength and prolong the life of pavements, reinforcement layers have been included in the design of most roads and highways. In this research, which is based on numerical simulations, the behavior of flexible pavement with respect to varying loads and with different reinforcement layers will be analyzed. The main objectives of this article are to develop a pavement layers model by utilizing finite element software, which is ABAQUS software package, evaluate the influence of different geogrid properties, location on the induced deformation, stresses, and strains into pavement layers and evaluate the influence of different loading values considering low, medium, and high traffic axle loads. The study reveals that stress on flexible pavements is directly proportional to load force, with stresses reaching 777 KPa at 44 KN and 1390 KPa at 80 kN. Deformations vary, with values ranging from 0.00307 mm at 44 KN to 0.00946 mm at 133 kN.

Ultra-thin Whitetopping (WT) is a technology in which a thickness of less than 100 mm of high early strength concrete pavement overlay is laid on a distressed bituminous pavement as a rehabilitation measure. WT modified by the application of Fiber-Reinforced Concrete (FRC) is adopted in this study. The three-dimensional finite element modeling developed in this study is for four-layered pavement with top fiber-reinforced WT layer, second bituminous layer, third sub-base, and bottom subgrade layer. Thickness and material properties of fiber-reinforced WT layer and bituminous layer are also varied for the parametric study. Loading is applied as per IRC:58-2015 and IRC:6-2010. Three different loading conditions such as interior, corner, and edge are considered, and maximum deflections at those loading positions are found out. The effect of temperature differentials is also studied. It is found that the deflection of fiber-reinforced WT pavement is maximum at slab corner, and it should be 5–10% times higher than edge and interior loading.KeywordsWhitetoppingPavementFinite element method

With the widespread utilization of composite pavements in highway tunnel projects, the flammability issue of asphalt layers has garnered increasing attention. Previous research has demonstrated that the addition of flame retardants effectively reduces the occurrence of pavement fires. However, there are few studies combining asphalt flame retardant technology with tunnel composite pavement structures. Therefore, this paper, considering the context of actual engineering projects, uses ABAQUS software to analyze and calculate the mechanical response of the tunnel composite pavement, considering the thickness of various asphalt layers under the ablation depth. Key design indexes such as shear stress and lower tensile strain of the asphalt layer, the bottom tensile stress of the cement concrete subgrade, and interlayer shear stress between the asphalt layer and cement concrete subgrade of composite pavements are analyzed using the nonlinear finite element analysis method. The findings enable the determination of the optimal thickness of the composite pavement asphalt layer combination after ablation, thus contributing to enhancing the safety of tunnel pavements.