Deflectometer Research Articles

Penerapan Soil Preloading, PVD, dan PHD untuk Analisis Penurunan Konsolidasi Tanah

Soft clay has a low bearing capacity, high compressibility and low permeability. This condition causes soft clay soil to have a long settlement time. To overcome this soft soil condition, soil improvement methods are needed. One of the efforts is to use a combination of soil preloading methods, Prefabricated Vertical Drain (PVD), and Prefabricated Horizontal Drain (PHD) methods. Calculating soil settlement with soil improvement is carried out using the Asaoka method, which is a field observation method, and the theoretical method using the Terzaghi method. Based on the calculation results of field observations using the Asaoka method, the average degree of soil settlement is 93.5%. The calculation results of the Asaoka method are recalculated using a back calculation to produce a new parameter value, namely the horizontal consolidation (Ch) value, which is then compared with the Ch value in the previous plan. In the Terzaghi method, the average soil settlement value is 1.205 meters. The results of soil settlement value are used to analyze the height of the embankment based on the load ratio requirement in SNI 8460: 2017, where the load ratio on the ground is ≥ 1.3 times the planned load under service conditions. Based on the monitoring results, a load ratio value of 0.875 was obtained so that the SNI requirements carried out a re-planning of the landfill. Then, proceed with the design of PVD and PHD. The results obtained in planning use triangular PVD patterns with a distance between PVDs of 1 meter.

Characteristics of stiffness–damping relationships in ballasted tracks for health condition evaluation

ABSTRACT The condition of ballasted track critically affects their safety and functionality. Several studies have focused on establishing guidelines for evaluating the condition of ballasted tracks. Light Falling Weight Deflectometer (LFWD) is considered as a quantitatively viable technique for conducting routine maintenance checks in Korea, serving as a potential replacement for impact sound assessment. LFWD measures the impact force applied to the sleeper and the resulting deflection, which provides the apparent stiffness and damping factor of the ballasted track. Finite element analysis (FEA) was adopted to simulate the LFWD tests as the ballasted tracks deteriorated. The FEA results revealed the influence of the deteriorated ballasted tracks on the stiffness-damping relationship. The characteristic curves of the apparent stiffness and damping factor derived from FEA were applied to investigate the condition of 12 ballasted tracks for high-speed trains in Korea. These investigations provided a visual representation of the progressive stages of deterioration in ballasted tracks.

Case Study: Validation of the Spectral-Analysis-of-Surface-Waves Method for Concrete Pavement Condition Evaluation

Before conducting pavement rehabilitation, the concrete pavement performance evaluation is more than necessary to assess the strength and analyze the internal condition. To evaluate the modulus performance of concrete pavement and provide theoretical support for subsequent maintenance and rehabilitation, the SASW (Spectral-Analysis-of-Surface-Waves) method, a non-destructive testing method based on surface waves, was used to determine the modulus of three in-service concrete pavements. At the same time, FWD (Falling Weight Deflectometer) testing and on-site coring were carried out at the measuring points. Through the analysis of modulus results measured in the field, it was found that the SASW method can accurately obtain the elastic modulus of the concrete layer and base layer. Compared with the concrete modulus measured by FWD, the modulus measured by the SASW method was closer to the uniaxial compressive modulus. Moreover, since the SASW method has the ability to provide gradient modulus varying with depth and determine the pavement thicknesses, it is reasonable to recognize the location of the inherent distress based on the region where the modulus suddenly decreases within one layer. The comprehensive evaluation of concrete pavement condition, including the modulus value and internal distress recognition, has the capability to assist in determining the design of overlay asphalt thickness and material.

Installation and Use of a Pavement Monitoring System Based on Fibre Bragg Grating Optical Sensors

The evolution of technological tools, namely affordable sensors for data collection, and the growing concerns about maintaining roads in adequate conditions have promoted the development of continuous pavement monitoring systems. This paper presents the installation and use of an innovative pavement monitoring system, which was developed to measure the effects of vehicle loads and temperature on the performance of a pavement structure. The sensors used are based on fibre Bragg grating optical technology, collecting data about the strains imposed in the pavement and the temperature at which those measurements are made. The site selection for the system’s installation and the essential installation details to ensure successful data collection are addressed. A calibration procedure was implemented by performing falling weight deflectometer tests and passing preweighed heavy vehicles over the sensors. In addition to validating the system installation, the results obtained in the calibration confirmed the importance of adequately choosing the distance between sensors. Differences of 50 mm in the position of the load may cause differences of about 20% to 25% in the resulting strains. These results confirmed the importance of increasing the sensor concentration in wheel paths. Furthermore, for loads between 25 kN and 65 kN, raising the temperature by 8 °C caused an increase of about 20% in the horizontal tensile strains measured in the pavement. In summary, it was possible to conclude that this innovative system is capable of capturing the effects of temperature and vehicle speed on the response of the pavement, which may be considered an advantage of this type of monitoring system when compared to those that are only used to determine the loads applied to the pavement or to characterise the type of vehicle.

Calibration of Effective Structural Number and Tensile Strain Models Using Traffic Speed Deflectometer (TSD) Data for Enhanced Project-Level Assessment on Flexible and Composite Pavements

Pavement deterioration models provide the basis for predicting future changes in network conditions, estimating future funding needs, and determining the effectiveness and timing of maintenance and rehabilitation activities. Determining the accurate structural condition of pavements helps identify effective maintenance strategies which enhance the sustainability and service life of pavements. This study aimed to use the Traffic Speed Deflectometer (TSD) and Fast Falling Weight Deflectometer (FFWD) for project-level evaluation of pavements and use pavement properties to calibrate current models that help to predict the structural condition of pavements. Model parameters were calibrated to determine the effective structural number and tensile strains at the bottom of asphalt concrete for asphalt and composite pavements from TSD deflections. Tensile strains from the KENLAYER highlighted varied behaviors for composite pavements. A significant improvement in the calibration was observed for asphalt concrete pavements. While the TSD has higher daily operational costs than FWD, its per-mile cost is significantly lower, making it a viable choice for extensive coverage, even though the quantitative results might differ between the two devices.

A Case Study on Distresses of Concrete Pavements Supported on a Retaining Wall

Embankments and retaining walls are integral parts of the bridge system and provide a smooth transition from lower elevations (i.e., roadways) to higher elevations (i.e., bridge decks). Performances of pavement structures supported on embankments or retaining walls are directly related to their conditions. This paper presents a comprehensive case study of the evaluation of pavement structures supported on an in-service mechanically stabilized earth (MSE) wall that showed significant distresses, such as lane separation, faulting, lane settlement, and tilting of the MSE wall. The conditions of the pavement structures were evaluated via visual observations, falling weight deflectometer (FWD) tests, and coring through pavement structures. The conditions of the MSE wall were evaluated through dynamic cone penetrometer (DCP) tests, cone penetration tests (CPTs), LiDAR surveys, and soil borings. Detailed analysis of the data obtained in this study provides valuable insights into potential distress mechanisms.

Large Temporal Variations of Functional Properties of Outdoor Equestrian Arena Surfaces and a New Concept of Evaluating Reactivity With Light Weight Deflectometer Settlement Curves.

Sports physiological properties of ten sand or sand-mineral outdoor arenas, five with vertical drainage systems and five with an ebb and flow like system were assessed over a period of 8 weeks. For each arena, the riding zone was spatially delineated, nine locations at medium to intensely used zones were selected by simple random sampling and used along the whole measurement period. A total of 72 values for the dynamic deflection modulus (Evd), attenuation (s/v), settlement (s) and moisture content (Vol %) were analyzed for each arena. A novel technique to analyze the settlement curves of the light weight deflectometer (LWD) to describe reactivity of the footing surface was introduced. Statistical testing was done by linear mixed models. Three of the five arenas with a vertical watering system were judged to be hard (Evd > 20 MN/m2), whereas all five arenas with an ebb and flow like watering systems were medium hard (Evd=10-20 MN/m2) over the entire 8 weeks. Significant (P < .01) temporal differences in Evd, s/v and moisture were demonstrated for both watering systems; however, the spatial and temporal variations were much lower with the ebb-flow system. Temporal consistency in the parameters over the test weeks appeared to be a criterion for stability of the arena surface. The analysis of the settlement curves of the LWD showed that the slope symmetry has a large potential to describe the restoration of the energy of an equestrian surface than only the settlement, which requires further validation.

Permanent Deformation Evaluation and Instability Prediction of Semi-rigid Pavement Structure Using Accelerated Pavement Testing and Finite Element Method

Abstract A rutting prediction method for semi-rigid pavement structures using accelerated loading tests and finite element analysis was proposed in this study. Firstly, dynamic modulus and creep tests of three pavement materials were performed by changing sizes and temperatures. The prediction equation was obtained and verified using the falling weight deflectometer test and back-calculation modulus, and it was coupled into a modified Burgers model for rutting simulation for full-scale pavement structures. Results showed that the dynamic modulus of pavement materials increased with increasing specimen sizes and decreased with increasing temperature. SUP-25 had an enormous fatigue damage value (0.419) after 5,400 times repeated loading. The error between the rutting simulation and test results was 2.87 %, indicating that the model effectively applies to multilayer composite materials. Rutting deformation at one million loading times in summer was 4.6 times that in winter. From 22 to 120 km/h, rutting deformation decreased by 72.6 %. Axle load increased by 100 %, and rutting depth increased by 46.9 %, indicating that vehicle overload should be restricted, especially in low-speed sections in high-temperature areas. Rutting deformation entered the accelerated accumulation stage when the cumulative action times were more than 25 million, which requires timely maintenance and repair of pavement structures.

Traffic Speed Deflectometer for Network-Level Pavement Management in Tennessee

The traffic speed deflectometer (TSD) overcomes the limitations of the falling weight deflectometer (FWD) with respect to traffic interruption and test inefficiency and is considered the preferred method for network-level pavement structural evaluation. However, some challenges exist when applying the TSD to routine survey work. This study evaluated the long-term repeatability of TSDs and compared TSD measurements with FWD measurements to examine device-related errors in TSD measurements. In addition, a framework for incorporating TSD measurements into the pavement management system (PMS) was developed by introducing deflection bowl parameters (DBPs). All data analyses were based on TSD data collected in Tennessee. From the current study, the repeatability of the TSD has not been fully validated because of device-related errors. Since TSD measurements and FWD measurements are broadly similar, periodic validation of TSDs by FWDs is recommended for quality control. TSDs provide valuable information about pavement structural conditions that are not reliably or adequately reflected in the current PMS (which focuses mainly on pavement functional conditions). DBPs are a simple and fast method for making initial estimates of pavement structural conditions without the need for layer thickness. In the proposed DBP system, the surface curvature index (SCI_12) and D60 (TSD deflection at 60 in. before the load center) represent the structural strength of the asphalt layer and subgrade, respectively. The combination of pavement functional conditions and TSD-measured structural conditions (PMS+DBPs) may help to make more accurate predictions of pavement performance and to make more appropriate decisions on maintenance and rehabilitation strategies.

An Approach for Adjusting the Laboratory-Determined Dynamic Modulus Master Curve of Asphalt Layers Based on Falling Weight Deflectometer Measurements

Structural assessment is critical for designing asphalt pavement overlays, estimating the remaining life of pavements, and selecting an appropriate rehabilitation strategy for existing pavements. The falling weight deflectometer (FWD) serves as the primary nondestructive test used for evaluating the in situ properties and structural capacity of asphalt pavements. The current procedure involves analyzing the FWD response and estimating layer moduli by assuming an elastic response. However, the response of asphalt layers is viscoelastic (i.e., temperature- and frequency-dependent). This study proposes an approach that combines FWD data with laboratory measurements of the dynamic moduli of field cores to determine the in situ viscoelastic properties of asphalt layers. This approach is implemented by analyzing FWD data from four pavement sections in Qatar. Furthermore, the paper includes a comparative analysis of the response of pavement sections in which the asphalt layers are modeled using dynamic modulus master curves obtained from laboratory tests and those obtained using the approach presented in this study. It was found that using the laboratory-based master curves overestimated pavement performance (i.e., underestimated pavement distresses). It is recommended to use the dynamic moduli from the method presented in this paper for a more accurate estimation of pavement response and performance.

Research on distresses detection, evaluation and maintenance decision-making for highway pavement in reconstruction and expansion project

Artificial walking survey, ground penetrating radar (GPR) and falling weight deflectometer (FWD) were used to test the actual condition of the highway pavement in reconstruction and expansion project for better maintenance decision-making. Therefore, a decision-making system with the application of four evaluation indexes including deflection value (DV), pavement surface condition within 20 m(PCI20), maintenance effect (ME) and internal crack rate (ICR) was constructed. Through the pavement empirical-mechanical calculation and the Delphi method analysis, the corresponding threshold for the DV, PCI20 and ICR were 27 (0.01 mm), 80, and 20 m/100 m2 respectively. Then, the decision-making system was applied for the 5.5 km section with the detection and evaluation results, and the advised maintenance plans of different lanes were determined. Lastly, the effect of the decision-making system was analyzed. Results show that the decision-making system can scientifically decide the treatment plans and save the maintenance cost by about 30.1 %. The deflection near the grouting holes significantly decreases resulting from the high-density cement slurry distribution. The milling and repaving have a high structural reinforcement ability of reducing deflection up to more than 66 %, which is positively related to the milling depth.

Effects of PLL Frequency Limiters on Synchronization Stability of Grid Connected VSC and Strategy to Realize Global Stability

This paper investigates the synchronization stability of voltage source converter (VSC) connected to infinite bus system with frequency limiter of phase-locked loop (PLL). First, three different types of PLL frequency limiters are modelled based on piecewise-smooth dynamical system (PSDS). Then the effects of different frequency limiters and frequency limit values on the region of attraction (ROA) of the system are studied and the properties of the PSDSs are analyzed. It is found that PLL with anti-windup limiter with back calculation can achieve global stability with appropriate limit value, and the principle of setting limit value based on a specific ROA estimation is proposed. Based on ROA estimation with Lyapunov function, a method of setting frequency limit value which guarantees global stability is proposed. The validity of the proposed strategy is verified through MATLAB/Simulink simulation.

A Case Investigation into Causes of Premature Rutting Failures in Rehabilitated Asphalt Pavements in Tanzania

Abstract Tanzania has faced high incidences of premature rutting failures on their asphalt pavements. Some pavements experienced failures within one to two years after construction/rehabilitation. The objective of this investigation was to identify the factors that contributed to the observed failures on five rehabilitated road sections on a national highway in Tanzania. Pavement temperature data collection, traffic surveys, visual inspection, rut depth measurements, and falling weight deflectometer tests constituted the main activities of the field investigation reported in this paper. The laboratory study included a visual assessment of cores extracted from the studied road sections to determine both physical and engineering properties, including density, stiffness, strength, aggregate shape properties, grading, and physiochemical tests on the recovered binders. The results of the study indicated that the degree and extent of rutting on the investigated road sections was rated as severe., i.e., rutting ranged from 38–138 mm on the five sections when compared to the acceptable threshold value of 15 mm for high volume roads in Tanzania. The elastic deflection results indicated that the underlying layers of the pavement system were generally in a sound condition, which validated the suggestion that the rutting observed was mostly confined to the asphalt concrete layers. Factors such as relatively high axle loads, poor asphalt mixes, and possibly inadequate quality control during construction and rehabilitation were suspected to contribute to the rutting on the sections. Practical measures recommended to the roads agency to avert future occurrences are provided in this paper.

Instrumentation of Field-Testing Sites for Dynamic Characterization of the Temperature-Dependent Stiffness of Pavements and Their Layers

Falling weight deflectometer (FWD) tests are performed worldwide for assessing the health of pavement structures. Interpretation of FWD-measured surface deflections turns out to be challenging because the behavior of pavement structures is temperature-dependent. In order to investigate the influence of temperature on the overall pavement performance and on the stiffness of individual layers, temperature sensors, asphalt strain gauges, and accelerometers were installed into one rigid (concrete) and two flexible (asphalt) pavement structures, mostly at layer interfaces. Three different methods for installation of the strain gauges are compared. From correspondingly gained experience, it is recommended to install a steel dummy as a place-holder into the surface of hot asphalt layers, immediately after their construction and right before their compaction, and to replace the dummy with the actual sensor right before the installation of the next layer. Concerning the first data obtained from dynamic testing at the field-testing sites, FWD tests performed at different temperatures deliver, as expected, different surface deflections. As for the rigid pavement, sledgehammer strokes onto a metal plate, transmitted to the pavement via a rubber pad, yield accelerometer readings that allow for detection of curling (=temperature-gradient-induced partial loss of contact of the concrete slab from lower layers). In the absence of curling, the here-proposed sledgehammer tests yield accelerometer readings that allow for quantification of the runtime of longitudinal waves through asphalt, cement-stabilized, and unbound layers, such that their stiffness can be quantified using the theory of elastic wave propagation through isotropic media.

Temperature effect on flexural bowl determined by falling weight deflectometer testing

The article presents the research results of the temperature influence on the flexural bowl on the road surface determined by falling weight deflectometer testing. The work relevance is conditioned by the high temperature effect of asphalt concrete on test results and the need to take it into account by bringing the results obtained at the actual temperature to a comparable form with the design data, when performing diagnostics of operating highways.Experiments identify the temperature factors that have an impact on the flexural bowl parameters. Temperature dependences are suggested for the flexural bowl on different road surfaces. A falling weight deflectometer is used to simulate the load produced by a moving truck, equipped with deflection meters located at the load center and various distances from it. Together with flexure bowl measurements, the temperatures of air, pavement and asphalt concrete at various depth is determined and dependences of these parameters are plotted.The paper identifies factors that have the greatest influence on the flexural bowl parameters. The results make it possible to bring flexural bowls into a form comparable with design values and subsequently use them to determine the overall bearing capacity of the pavement as well as to assess the condition of individual structural layers, thereby increasing the reliability of repair measures.

Strength and stiffness characterizations of geo-materials composing unpaved roads using LFWD, DCP, and CDP tests

To assess the condition of the geomaterials composing unpaved roads subjected to cyclic wheel loads by moving vehicles, it is necessary to evaluate the variations in mechanical properties with depth. In this study, a crosshole-type dynamic cone penetrometer (CDP) was applied to characterize the stiffness of unpaved soil along its depth. In addition, light falling weight deflectometer (LFWD) and dynamic cone penetrometer (DCP) tests were conducted for a comparative analysis. The LFWD, DCP, and CDP tests were conducted on a newly constructed unpaved road after the application of 0, 200, and 400 cycles of wheel loads by a moving vehicle. From the experimental results, the strength and stiffness properties such as Evd, NDCP, and Vs, were obtained, and their incremental ratios were investigated according to the number of cyclic wheel loads. In addition, the improved relationships between Evd, NDCP, and Vs were constructed considering the strain influence factors with depth. This study demonstrates that CDP can be an efficient testing method to profile the stiffness of unpaved roads, and the relationships considering the strain influence factors may be used effectively for reasonably estimating the engineering properties.

Machine learning based inversion for earth rock dam compaction density

In water resources and hydropower engineering and highway engineering, the compactness test of earth-rock mixed materials of the earth-rock dam and embankment plays an important role for construction quality assessment. The key is how to accurately and quickly evaluate the compaction density, which requires advanced methods. Meanwhile, machine learning has become an important and powerful tool for parameter prediction. In this work, a method to obtain the compactness of an earth-rock dam using machine learning algorithms is developed and verified. In so doing, first, by analyzing and processing the measured time history signal from a new fast Portable Falling Weight Deflectometer (PFWD), including time domain, frequency domain and mechanical impedance analyses, six optimized characteristic parameters are obtained to invert for the compactness, including the stiffness coefficient, the maximum time difference, the maximum amplitude ratio, the central frequency difference, the maximum stiffness impedance and the resonance frequency. Pearson coefficient was used to analyze the correlation among the six parameters and Gini index was used to analyze the influence degree of the parameters on the relative wet density. Then, the Decision Tree (DT) model, Random Forest (RF) model and Gradient Boosting Decision Tree (GBDT) model were used to predict the wet density and dry density of materials, respectively, and compared. PFWD was applied on a dam to acquire the time history signal, which was then preprocessed following a series of procedures including integrity check, outlier handling and normalization etc, and machine learning algorithms were used for training the data and parameter prediction. Examples show that, considering the generalization and optimization ability, for the GBDT model, the root-mean-square error (RMSE) of the predicted wet density of the earth-rock material is within 0.041 g/cm3 and that of the predicted dry density is within 0.032 g/cm3, which meet the requirements for construction detection and quality control. The proposed method based on PFWD signal analysis and machine learning algorithm models help better solve the nonlinear mapping problem between the PFWD signal and material density, and can accurately invert for the wet density and dry density of materials. It is an effective way for rapid detection and control of earth-rock dam construction quality.

Dynamic global power extraction of partially shaded PV system using a hybrid MPSO-PID with anti-windup strategy

Particle Swarm Optimizer (PSO) has three main drawbacks in case of partially shaded photovoltaic systems. First, it converges slowly to the global peak (GP). Second, because PSO is a time invariant, it cannot adhere to a dynamic GP in the presence of various temporal shading patterns and instead, sticks to the first GP. Third, it exhibits high oscillations around GP. To overcome these shortcomings, this paper proposes a novel hybrid modified PSO-PID (MPSO-PID) with anti-windup strategy based maximum power point tracking. The anti-windup strategy aims to guarantee the robustness of the PID controller and eliminate the PID windup outcome. Two anti-windup structures were applied to PID namely: anti-windup using back calculation and anti-windup using conditional integration. For validation purpose, the hybrid MPSO-PID with anti-windup has been compared with conventional PSO and three modified PSO versions namely: PSO with random numbers eliminated (PSO-RNE), PSO with linearly varying parameters (PSO-LVP), and PSO with fixed maximum iterations (PSO-FMI). The obtained simulation and experimental results revealed that the proposed MPSO-PID with anti-windup overcome the previous shortcomings providing outperformance to track dynamic GP with a less convergence time and small oscillations around GP compared to other algorithms. The proposed MPSO-PID technique has a minimum average response time; 0.026 s; to catch the GP under various shading patterns compared to the other PSO versions; CPSO, PSO-LVP, PSO-RNE, and PSO-FMI; where the average response time are 0.026 s, 0.531s, 0.446 s, 0.763 s, and 0.494 s respectively. Finally, the results proved the robustness and effectiveness of PID design for enhancing both the PSO and PV system performance.

Influence of Spring Stiffness on the Loading Speed of the Falling Weight Deflectometer (FWD) in Bearing Capacity Evaluation of Cement Concrete Pavement

Introduction: The bearing capacity evaluation of cement concrete runway pavement is one of the most important contents in the airfield operation. Among the methods for estimating bearing capacity, the Falling Weight Deflectometer (FWD) is the most widely used method because it does not damage the pavement structure and spends so much time. The equipment for evaluation should have suitable parameters, such as. magnitude and loading speed, to the actual operating loads. Aims and Objectives: Currently, the equipment to assess the bearing capacity of cement concrete pavements of highways and airports by falling weight has been widely used in the world and is being applied in Vietnam. The loading system consists of a falling block through a spring system acting on the pressure plate under the pavement with a certain falling height. In particular, the spring system plays an important role in controlling the speed of the load on the pavement. In Vietnam, the test standards (Industry Standard 22TCN335-06, Vietnamese Standard TCVN 11365-2016) for assessing the pavement bearing capacity by FWD equipment do not specify the selection of spring stiffness corresponding to different operating speeds of the vehicle. Therefore, it is difficult to use the equipment for pavements with operating speeds different from the standard. In this paper, we study the effect of spring stiffness on the loading speed when considering different loading speeds corresponding to different speeds of vehicles moving in reality. This research is only limited to laboratory experiments. This study aims to determine the dependence of the loading magnitude and loading time on the damping spring stiffness of the dynamic loading equipment, that is, used as a basis for choosing the appropriate damping stiffness of FWD corresponding to actual vehicles. Methods: Among the methods for estimating the bearing capacity, the Falling Weight Deflectometer (FWD) is the most widely used method as it does not cause any damage to the pavement structure and spends much time. The equipment for evaluation should have suitable parameters, such as magnitude and loading speed, to the actual operating loads. Results: This paper presents the results of experimental research that determines the influence of the damping spring stiffness on the loading speed of the dynamic loading equipment on the model of the concrete slab in the laboratory. Conclusion: Based on the comparison of the FWD loading speed when using 02 damping springs with different stiffness, we propose the basis for choosing the damping system that conforms to the evaluation needs of different types of vehicles.

Proposing Binary Gravitational Search Algorithm Parameters for Back-calculation of Road Pavement Moduli

A Falling Weight Deflectometer is popular equipment to measure surface deflections under imposed loadings, providing the necessary parameters for back-calculating the elastic moduli of road pavements. There are several back-calculation programs available that accurately back-calculate pavement layer moduli. The Gravitational Search Algorithm (GSA), a metaheuristic optimization algorithm inspired by Newton’s law of universal gravitation, is one such algorithm. The Binary Gravitational Search Algorithm (BGSA) is an enhancement algorithm based on GSA that can be used as an efficient search algorithm for back-calculating pavement moduli based on matching measured and calculated surface deflection of road pavements. Choosing the best BGSA parameters is critical for accurate back-calculation of road pavement moduli. Nevertheless, there has not been much study on selecting the best BGSA parameters for back-calculating road pavement moduli in the literature. Therefore, this study proposes strategies for selecting BGSA parameters based on the least computational effort and the least root mean square error between measured and calculated road pavement surface deflections. In this study, the Burmister theory is discussed and the Richardson extrapolation is adopted to improve the accuracy of the calculated points near the pavement surface; the best parameter of BGSA including the agent size A of 50 and an iteration step T of 300 are suggested to back-calculating the road pavement moduli.