Deflectometer Research Articles

FIELD PERFORMANCE OF HOT IN-PLANT PRODUCED ASPHALTIC CONCRETE WEARING COURSE (ACWC) WITH 30% RECLAIMED ASPHALT PAVEMENT (RAP)

Hot in-plant recycling stands as an effective yet underutilized method in Malaysia for reusing pavement milling waste, resulting in insufficient established benchmarks and validated trials. The Utilization of Reclaimed Asphalt Pavement (RAP) can divert a significant amount of waste asphalt millings from landfills, while conserving energy and natural resources. This study focused on the recycled mixture, ACWC-30RAP, which integrated 30% Reclaimed Asphalt Pavement (RAP). In July 2022, a 400 m trial lay was conducted from KM413.90 to KM414.30 Southbound (SB), Section C3, along the PLUS North-South Expressway (NSE). Field tests were systematically conducted on both the ACWC-30RAP and conventional ACWC20 mixtures at different phases including month-6, month-9, and month-12 post-construction. The primary objective was to assess fundamental properties related to the structural stiffness of pavement layers as well as the pavement performance and condition for both trial sections using various field testing including Falling Weight Deflectometer (FWD) and Multi-Laser Profiler (MLP). Following the 12-month trial period, both the ACWC-30RAP and conventional ACWC20 mixtures experienced actual traffic loading and environmental conditions. Remarkably, the ACWC-30RAP demonstrated comparable field performance as the conventional ACWC20. This alignment in performance signified a promising avenue for employing the recycled mixture with high RAP content. Using ACWC-30RAP can also provide economic benefit, reducing the production cost by approximately 25%. In essence, the ACWC-30RAP had achieved an equivalent level of confidence to the conventional ACWC20 mixture, which was exclusively composed of virgin materials. cts.

Constrained Control of Autonomous Underwater Gliders Based on Disturbance Estimation and Tracking Back Calculation

ABSTRACTThis article presents an anti‐disturbance constrained control scheme for the pitch channel of autonomous underwater gliders subject to internal and external disturbances, as well as actuator saturation. First, the integral control technique is employed to develop a disturbance observer to estimate the overall effect of possible uncertainties and disturbances on the nominal vehicle model, which is referred to as the mismatched lumped disturbance. Then, a disturbance rejection control law is constructed based on the disturbance observer. Following that, a straightforward anti‐windup modification is proposed to handle potential input constraints by using the tracking back calculation technique. Specifically, the difference between saturated and unsaturated control input signals is utilized to create a feedback signal that addresses the disturbance observer input, thereby alleviating system windup during actuator saturation events. Furthermore, the stability of the overall closed‐loop system is established in term of the Lyapunov stability theorem, demonstrating that the tracking error is ultimately bounded. Compared with some existing anti‐windup control schemes, the suggested approach offers intuitive design guidelines, resulting in a simple controller that can be easily implemented. Finally, the effectiveness and robustness of the proposed control scheme are verified through simulation results.

Structural condition assessment of asphalt pavement semi-Rigid bases using FWD deflection basin parameters

Assessing structural conditions of semi-rigid bases in asphalt pavements is essential for effective base treatment in reconstruction and expansion (R&E) projects. Although various falling weight deflectometer (FWD) parameters have been developed for this purpose, field-validated parameters are still missing. This study identifies the appropriate FWD deflection basin parameter (DBP) through sensitivity analysis, correlation examination, and on-site milling and inspection. Findings indicate D20-D60 as the most suitable DBP, with 23 µm and 40 µm thresholds for warning and severe conditions, respectively. The correlation between D20-D60 and cracking rate suggests that high cracking rates suggest base weakness, whereas low rates may not guarantee structural integrity due to maintenance masking effects. On-site milling further confirmed this finding, demonstrating the alignment between D20-D60 assessments and field observations. The outcome of this study is anticipated to provide a practical DBP for evaluating semi-rigid base conditions and to inform base treatment strategies in R&E projects.

Correlative Study of Light-Weight Deflectometer, Plate Loading, and California Bearing Ratio Tests for Unbound Pavement Layers Using Genetic Algorithm

Correlative Study of Light-Weight Deflectometer, Plate Loading, and California Bearing Ratio Tests for Unbound Pavement Layers Using Genetic Algorithm

Fatigue cracking prediction of cobblestone interlayer pavement using non-destructive testing and mechanistic-empirical analyses

Several non-destructive testing (NTD) methods have been used to measure surface deflection, which makes to determine the elastic moduli of pavement layers through the back-calculation process and assess the structural capacity of asphalt pavements. In this study was evaluated the back-calculated moduli of the cobblestone interlayer pavements and the load capacity of this type of pavement related to the fatigue cracking criterion based on a mechanistic-empirical analysis. The employed methodology included the performance of on-site trials using non-destructive testing with the Falling Weight Deflectometer (FWD) devices on 84 test points in granular and cobblestone interlayer pavements, determination of deflection basin parameters (DBP), back-calculation layers’ moduli, and estimate of the fatigue cracking performance of the pavements by mechanistic-empirical analyses in MeDiNa software. The pavements with a cobblestone base layer displayed greater deflection measurements on the load application point compared to those measured on pavements with a granular base layer, indicating that conventional pavement displayed more stiffness. Cobblestone interlayer pavement displayed greater amounts of cracked area compared to granular base layer pavements showing lower load capacity based on the fatigue criterion. The DBP-based method by FWD test was able to identify the structural differences between the layers of pavements evaluated and identify the cracking evolution.

Asphalt pavement structural competency during staged airfield runway construction strategy

ABSTRACT This paper reports the results from a full-scale evaluation of asphalt pavement structural competency during a multi-stage construction strategy. The staged pavement construction included three stages: (1) new conventional asphalt pavement, (2) unpaved full depth reclaimed (FDR) pavement, and (3) thin surface asphalt paved FDR layer. The full-scale pavement sections consisted of a standard and substandard pavement structural design. The accelerated pavement testing (APT) experiments were executed by simulating the loading conditions of an aircraft with a critical combination of relatively high wheel load and high tire inflation pressure. The structural capacity of the pavement test items was monitored using a falling weight deflectometer. From this study, the staged pavement construction concept was found to be a potential approach to extend the service life of asphalt pavements. Unpaved FDR layers are structurally competent to support a low volume of aircraft operations. These findings support the transition to the use of asphalt pavements containing an FDR layer from an experimental to routine rehabilitation practice for airfield asphalt pavements.

Machine Learning Approach to Rapidly Evaluate Curling of Concrete Pavement

This paper focuses on the methodology for evaluating the degree of total curling in concrete pavement using machine learning. Deflection induced by falling weight deflectometer (FWD) testing is known as a direct correlation to total curling including built-in and daily curling. However, deflection measurement in the in-service road is also affected by others, such as environmental conditions, pavement geometry, subgrade stiffness, and mixture design. Thus, it is challenging to determine the level of curling from FWD data due to the complexity of influencing parameters. To navigate this complexity, prominent machine learning models are exploited to identify a non-linear relationship between curling and FWD deflections. A finite-element simulation of FWD is conducted to generate a vast data set, and a robust regression model is trained to estimate the total effective temperature difference (TETD) to quantify the effects of curling. Since input parameters for testing pavements can be measurable in the field, curling from TETD can be readily obtained using the proposed methodology. Comparative simulations highlight that the proposed models, with an MAE less than 0.5 °C significantly outperform the multiple regression performance, which registers an MAE of 3.45 °C in TETD, particularly in offering cost-effective and noise-tolerant prediction.

Enhanced in-situ measurement and evaluation methods for subgrade modulus utilizing falling weight deflectometer

Falling Weight Deflectometer (FWD) tests have gained increasing popularity in evaluating the stiffness modulus of pavement subgrade. This paper presents an enhanced method for in-situ testing and evaluation of subgrade modulus using FWD apparatus. The method comprises three components: 1) guidelines for conducting field FWD tests with appropriate loading magnitudes and repetitions; 2) selection of optimal deflection positions for modulus back-calculation; and 3) determination of the suitable depth of the semi-infinite rigid layer. This method was developed based on measurements and analysis of FWD data from five highway subgrade sites, covering various subgrade soil types and climatic conditions. The enhanced method helps to promote the robustness and accuracy of modulus back-calculation results. Furthermore, to validate the proposed method, the back-calculated modulus was compared with moduli obtained from the other two commonly used tests, named the Portable Seismic Pavement Analyzer (PSPA) modulus test and the triaxial modulus test. Comparison results indicate strong correlations between the modulus values obtained from the proposed method and those from the PSPA and triaxial modulus tests, affirming the practicality of the proposed method in determining subgrade stiffness modulus.

Deep learning-based inversion of soil and rock compaction density utilizing Falling Weight Deflectometer (FWD) and Surface Waves

Methods relying on a single dynamic parameter to estimate the material density for the compaction quality testing of earth-rock dams and roadbed projects, present certain limitations in terms of applicability, testing accuracy, and work efficiency. The theory of elastic wave propagation reveals that the compaction density of the medium results from the combined interaction of multiple material properties. This study proposes a method that utilizes the transient surface wave method and a vehicle-mounted Falling Weight Deflectometer (FWD) to jointly enhance the accuracy of soil and rock material compaction detection. The transient surface wave method is employed to extract surface wave velocity and compressional wave velocity. The analysis of the FWD signal involves extracting dynamic parameters closely related to material density, including stiffness coefficients, central frequencies, and stiffness impedances, from time-domain, frequency-domain, and mechanical impedance analyses. A fully connected deep neural network is introduced to intelligently estimate the compaction density. The deep learning model is optimized by selecting the optimal activation function and optimization algorithm, as well as additional tuning. Extensive testing shows that deep learning model produce results closely approximating the true compaction density values. The average relative errors for the wet density and the dry density are 2.9% and 2.85%, respectively, meeting the quality control requirements for density testing. The proposed approach enables rapid detection and control of the compaction quality of soil and rock materials, providing a new method for the in-situ rapid detection of compaction quality.

Consistency Testing of Light Weight Deflectometer (LWD) Tool Pusjatan on Composite Road (Case Study of Road Section Soreang New Ring Road, Bandung Regency)

In an era of rapid technological and infrastructural development, the quality of roads is critical to ensuring efficient and safe mobility. Composite roads, which consist of a mixture of different types of construction materials, have become an attractive option in road development in various regions. However, to ensure the success of composite roads, structural consistency and performance must be considered. A Light Weight Deflectometer (LWD) is a device used to measure the instability of road layers by applying surface pressure and measuring the resulting deflection. Although the use of LWD is common in the road construction industry, specific research on LWD consistency testing of composite roads is limited. This study investigates and analyzes the consistency of LWD on composite roads to improve the understanding of its performance. The results of the study on composite pavements conducted at three points with 30 trials showed a coefficient of variance of less than 5%. This result indicates very strong data consistency. Based on these consistency values, the LWD is acceptable, but it needs to be correlated with other tools to determine its validity. If the consistency and correlation meet the requirements or are less than 5%, LWD has a good chance of being used in composite pavements.

Calculation Thickness of the Added Flexural Layer on Composite Layer using a Light Weight Deflectometer (LWD) Pusjatan

Calculating the thickness of the flexible overlay needs to consider several factors, such as traffic load, soil characteristics, existing pavement conditions, and planned changes to the road design. This procedure generally uses recognized pavement design methods, such as the AASHTO 1993 method (Guide for Design of Pavement Structures). This research aims to determine the thickness of the added layer using an asphalt layer on composite roads in accordance with the 1993 AASHTO standards. It is hoped that this method can produce an effective overlay design, extend the life of the pavement, and increase the comfort and safety of road users. The data used in this research includes primary and secondary data. The results of this analysis are to calculate the STA 0 segment, for other STAs use the same method. From the Light Weight Deflectometer (LWD) deflection data, the Subgrade Reaction Modulus (k) value was 473 psi/in, the Concrete Elasticity Modulus (Ec) value was 4,843,105 psi and the Rupture Modulus (Sc') value was 699 psi. The traffic load used is 25.000.000, so the result of calculating the plate thickness to serve future traffic (Df) is 10.79 inches or 27.40 cm and the effective plate thickness value (Deff) is 9.13 inches or 23.30 cm, then the result is the added layer thickness (Dol) is 3.30 inches or 8.39 cm

Modelling permanent strain behaviour of soil for flexible pavement design utilizing LWD measurements

ABSTRACT This study aims to improve understanding of unbound material behavior by modeling permanent strain using Light Weight Deflectometer (LWD) measurements, as part of VTI’s broader LWD research. By comparing permanent strain modelling from LWD data with Repeated Load Triaxial (RLT) tests on silty sand soils, it validates LWD data accuracy and explores material property influences on permanent strain parameters, revealing a clear correlation with water content and stress levels. Using LWD data validated against RLT tests, the study delves into material behaviour understanding under varied conditions, focusing on comparing model parameters of permanent strain prediction derived from LWD and RLT tests. Despite minor differences, both methods produce acceptable values, affirming the modelling approach’s robustness. The findings demonstrate LWD’s potential to improve pavement design by providing insights into permanent strain behavior that supports mechanistic-empirical approaches, leading to more efficient designs and better resource use for improved performance.

Verification and Analysis of the Pavement System Transfer Function Based on Falling Weight Deflectometer Testing

Verification and Analysis of the Pavement System Transfer Function Based on Falling Weight Deflectometer Testing

Sustainable Design of Pavements: Predicting Pavement Service Life

Pavement service life is an important factor that affects both the whole life cost and carbon footprint of a pavement. The service life of a pavement is affected by several different parameters which can be broadly classified into climate conditions, binder and mixture properties, pavement design, workmanship, and maintenance strategies. The current practice for determining service life of pavements involves the use of pavement design tools, which are used while constructing a new pavement or performing a reconstruction/resurfacing or pavement maintenance. In addition, field measurements using ground penetration radar, falling weight deflectometer, traffic speed deflectometer, and other techniques are also used to assess the condition of an existing pavement. The information from these measurements is then combined with pavement design software to predict potential pavement service life. The accuracy of the predicted pavement service life is affected by the associated uncertainties in the parameters that affect pavement life. The following paper presents various approaches that could be potentially used to determine the associated uncertainties in the estimation of pavement service life. The various uncertainty quantification techniques have been applied to a specific design, and the outcomes are discussed in this paper. The Monte Carlo simulation method, a system-level uncertainty quantification technique, can estimate a probabilistic pavement service life. The other uncertainty quantification schemes are software specific and provide probabilistic life factors by assumed statistical distributions. Hence, the Monte Carlo simulation technique could be one potential method that can be used for estimating a generalized pavement service utilizing predictions from various design software.

Hubungan Penilaian Kerusakan Jalan Metode Bina Marga dan Light Weight Deflectometer (LWD)

The Tegal Siwalan-Banyuanyar Highway in Probolinggo Regency has been damaged at several points and has not received any maintenance for the last 7 years. This has a huge impact on road users because it can interfere with driving comfort and safety, so it is necessary to analyze the road damage that has occurred, including the type of damage and an assessment of road conditions. The Bina Marga method and a light-weight deflectometer (LWD) can be used to assess road deflection in order to assess road condition. The results of this study obtained priority order values for each segment that were in the range 5-11. The greater the value of the Order of Priority obtained, the better the road condition, whereas the smaller the value of the Order of Priority obtained, the worse the road condition. It was also found that the Bina Marga method and the Light Weight Deflectometer (LWD) tool had a poor correlation, so a comparison between the two could not be made for assessing the condition of the road surface layer.

The Impact of Dynamic Effects on the Results of Non-Destructive Falling Weight Deflectometer Testing.

The article investigates the impact of applying a dynamic computational model that considers inertia forces on pavement deflections under rapidly changing loads over time. This study is particularly relevant to the modelling of falling weight deflectometer (FWD) testing. Initially, the article examines the deflection values obtained from computational models under loads with varying frequencies. In this context, considering inertia forces was significant for load durations shorter than 0.04 s. In such cases, the results of static and dynamic analyses differed considerably. One application of FWD measurement results is determining the stiffness moduli of pavement layers using backcalculation. The study explored the impact of incorporating inertia forces into the pavement model on the estimated values of stiffness moduli obtained via backcalculation. The results revealed differences of several percent between the stiffness moduli calculated using dynamic and static numerical models. Subsequently, the key pavement deformations and fatigue life were determined using the obtained moduli. Again, significantly different results were observed between dynamic and static cases. Based on these findings, it can be concluded that dynamic effects should not be ignored when using FWD testing for backcalculation. Additionally, the article addresses the sensitivity of backcalculation results, which is crucial for the accurate interpretation of the obtained data.

Comparative Evaluation of Falling Weight Deflectometer, Traffic Speed Deflectometer and Rapid Pavement Tester in Deflection Measurement

This study intends to compare deflections obtained from traffic speed deflection devices (TSDDs) with the deflections of the falling weight deflectometer (FWD). For this purpose, deflections were measured on five sections of three roads in the Norwegian road network using traffic speed deflectometer (TSD) and rapid pavement tester (Raptor). Deflections were also measured using FWD at three different temperatures and the curves of FWD deflections versus temperature (FWD temperature-dependent deflection curves) were obtained. These curves were used to correct the effect of temperature difference. It was shown that both TSD and Raptor have the potential to detect structural deficiencies; however, TSD had better consistency with FWD with regard to deflection values and deflection basin parameters. A refinement was then made to make the Raptor data more consistent with FWD data. Calculating bearing capacity before and after refinement revealed that refining Raptor data can substantially increase the consistency between Raptor and FWD.

Study on Dynamic Modulus Prediction Model of In-Service Asphalt Pavement

The dynamic modulus of in-service asphalt pavements serves as a critical parameter for the computation of residual life and the design of overlays. However, its acquisition is currently limited to laboratory dynamic modulus testing using a limited number of core samples, necessitating a reassessment of its representativeness. To facilitate the prediction of dynamic modulus design parameters through Falling Weight Deflectometer (FWD) back-calculated modulus data, an integrated approach encompassing FWD testing, modulus back-calculation, core sample dynamic modulus testing, and asphalt DSR testing was employed to concurrently acquire dynamic modulus at identical locations under varying temperatures and frequencies. Dynamic modulus prediction models for in-service asphalt pavements were developed utilizing fundamental model deduction and gene expression programming (GEP) techniques. The findings indicate that GEP exhibits superior efficacy in the development of dynamic modulus prediction models. The dynamic modulus prediction model developed can enhance both the precision and representativeness of asphalt pavement’s dynamic modulus design parameters, as well as refine the accuracy of residual life estimations for in-service asphalt pavements. Concurrently, the modulus derived from FWD back-calculation can be transmuted into the dynamic modulus adhering to a uniform standard criterion, facilitating the identification of problematic segments within the asphalt structural layer. This is of paramount importance for the maintenance or reconstruction of in-service asphalt pavements.

Coordination of the back flashover probability of HVAC and HVDC on a hybrid transmission tower

The demand for power transfer has increased throughout the green transition, especially as power generation is becoming increasingly decentralized. However, constructing new transmission lines and towers has met with public opposition. One option to increase transmission capacity while minimizing the erection of new towers is to use hybrid HVAC-HVDC multi-circuit towers. If not carefully designed, considerably more back flashovers could occur to the more vulnerable DC circuit. This paper investigates the effect of a change in insulator size on the ratio of back flashovers between AC and DC circuits on the same hybrid tower by using a PSCAD model with HVAC-HVDC hybrid towers. A back flashover ratio calculation method is developed and used in combination with an algorithm to provide a DC insulator length based on a predetermined back flashover ratio. The algorithm allows for faster design of the insulator sizes for a multi-circuit tower, coordinating the ratio of back flashover probabilities to either the HVAC or the HVDC circuit.

Field Evaluation and Application of Intelligent Quality Control Systems

During road construction, the accuracy of compaction work is critical for the structural stability and maintenance of the road. Although the plate load test (PLT) is commonly used for quality inspections, it is impractical to test every section due to time and cost constraints. Therefore, simpler testing methods are being extensively developed. This study compared quality inspection results using the commonly used PLT, the relatively simple dynamic cone penetrometer test (DCPT), the lightweight deflectometer (LWD) test, and an intelligent quality control system equipped with accelerometer and global positioning system (GPS) sensors in intelligent compaction (IC) rollers. The results showed a strong correlation between the conventional tests (PLT, DCPT, and LWD) and the values obtained from the intelligent quality control system. The correlation analysis between the intelligent quality control system and PLT, LWDT, and DCPT yielded R-square values of 0.69, 0.91, and 0.95, respectively, indicating significantly high correlations. The implementation of intelligent quality management systems in earthwork construction projects will facilitate a thorough verification of the compaction quality throughout all construction segments, ensuring consistent compaction across the project. By enabling real-time data acquisition and analysis, these systems differ markedly from traditional methods, reducing the frequency and necessity of manual inspections. This approach not only streamlines construction processes, but also enhances operational efficiency. As a result, integrating these intelligent systems is anticipated to significantly increase productivity by optimizing the workflow and resource utilization in earthwork construction.