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1.
Kam Ng Daniel Hellrung Khaled Ksaibati Shaun S. Wulff 《International Journal of Pavement Engineering》2018,19(1):62-74
A research focusing on the characterisation of representative local material properties was conducted to facilitate the full implementation of the Mechanistic-Empirical Pavement Design Guide for roadway designs in Wyoming. As part of the test program, falling weight deflectometer deflection data were collected from 25 test sites in Wyoming for back-calculation of subgrade resilient modulus. Also, subgrade materials from these test sites were sampled for laboratory resilient modulus measurement in accordance with the AASHTO T 307. The back-calculation is a user-dependent procedure and produces a non-unique resilient modulus estimation. To alleviate this limitation, this paper focuses on the recent development of a systematic back-calculation protocol for subgrade resilient modulus using MODCOMP6 software. The protocol is intended for use on a flexible pavement with a crushed base. The proposed procedure discusses pre-analysis checks, seed modulus adjustment, pavement structure adjustment and program termination criteria. A correlation study was conducted to correct back-calculated resilient modulus to laboratory-equivalent values. The results conclude that a non-zero intercept linear regression model provides a better correlation than the widely used zero intercept linear regression model. Furthermore, better correlations are achieved when the back-calculated resilient modulus of a lower subgrade layer and resilient modulus measured at higher laboratory test sequences Nos. 11 to 15 are considered. The non-zero model based on Mr test sequence No. 14 and lower subgrade layer yields the best correlation. For the zero model, a C-factor of 0.645 based on Mr test sequence No. 15 and lower subgrade layer yields the best correlation. 相似文献
2.
《International Journal of Pavement Engineering》2012,13(2):146-153
This paper presents the statistical analysis results for correlating the stiffness characteristics of subgrade with subgrade soil properties using the long-term pavement performance database in the USA. The stiffness of subgrade soils was characterised by the falling weight deflectometer deflection basin parameters and subgrade modulus calculated using the backcalculation technique. For the statistical approach, both linear fixed- and mixed-effects models were applied to estimate the correlation between subgrade stiffness and soil properties. It is found from this study that the base curvature index and subgrade modulus are highly correlated with subgrade soil properties and variation of water content. The results also indicate that the mixed-effect model can accurately estimate the stiffness of subgrade soils using the soil properties and water content. Region-specific factors considered as the sources of random effects in the mixed-effects model can help to improve the degree of correlation. 相似文献
3.
《International Journal of Pavement Engineering》2012,13(7):609-619
A full-scale accelerated pavement testing was conducted with Mobile Load Simulator 66 in Chongming Island, Shanghai, to study the performance response of a semi-rigid base asphalt pavement with fine-sand subgrade designed for the G40 construction. As an index sensitive to temperature and load, three different moduli including the seismic modulus, field falling weight deflectometer back-calculation modulus and interior material testing system resilient modulus were all measured during and after the test. The modulus evolution of asphalt pavement with the loading applications, rutting, strain and temperature, and the comparison of three methods for measuring modulus were analysed. There exists a modulus gradient from top to bottom, which can be considered in the pavement design or fatigue life prediction. Because of the strain level differences, the seismic modulus was the largest, followed by back-calculation and resilient modulus; the development of seismic and back-calculation modulus better reflected the anti-deformation changes. 相似文献
4.
《International Journal of Pavement Engineering》2012,13(4):388-402
This study presents a revised approach to conceptualising and analysing data from the traffic speed deflectometer (TSD) which enables full deflection bowl predictions. The approach was successfully applied to TSD surface velocity measurements collected at seven test sites as part of recent Australian trials. More than 1500 deflection bowls produced from the TSD data were validated against approximately 600 40- and 50-kN falling weight deflectometer (FWD) deflection bowl profiles. Overall, the results showed a clear correlation between the shape and magnitude of deflection bowls predicted by both methods. Estimates of maximum deflection (d 0) and structural curvature index (SCI300) from both methods were also compared, showing a strong correlation. The results suggest that the TSD device has significant potential to be used to collect measurements of pavement deflection bowls at highway speeds which are comparable with FWD deflection bowl measurements. 相似文献
5.
《International Journal of Pavement Engineering》2012,13(2):110-125
This paper discusses the variability of in-situ physical and mechanistic characteristics of three construction projects using non-destructive test (NDT). Six sites from each project in the state of Louisiana were selected. Three NDT tests – falling weight deflectometer (FWD), light falling weight deflectometer (LFWD) and pavement quality indicator (PQI) – were carried out during and after construction. The deflection data from FWD and LFWD were utilised to backcalculate in-situ layer moduli and composite moduli, respectively. ELMOD and MICHBACK backcalculation softwares were used to calculate and compare the hot mix asphalt (HMA) layer moduli. The in-situ density of the HMA layer was obtained from the PQI device. Project variability in the in-situ measurements of the HMA layer was attributed to HMA layer thickness, temperature and seasonal variations. It was found that there was a good relationship between the HMA composite moduli calculated using the FWD deflection and Bossinesq's equation and moduli from the LFWD. The results also indicated that there was no strong relationship between the in-situ moduli and in-situ PQI voids. 相似文献
6.
Sudhir Varma 《International Journal of Pavement Engineering》2016,17(5):388-402
Appropriate characterisation of individual layer properties is crucial for mechanistic analysis of flexible pavements. Typically in inverse analyses, pavements are modelled as elastic or nonlinear elastic to obtain layer material properties through non-destructive falling weight deflectometer (FWD) testing. In this study, a layered viscoelastic–nonlinear forward model (called LAVAN) was used to develop a genetic algorithm-based backcalculation scheme (called BACKLAVAN). The LAVAN can consider both the viscoelastic behaviour of asphalt concrete (AC) layer and nonlinear elastic behaviour of unbound layers. The BACKLAVAN algorithm uses FWD load-response history at different test temperatures to backcalculate both the (damaged) E(t) and |E*| master curve of AC layers and the linear and nonlinear elastic moduli of unbound layers of in-service pavements. The BACKLAVAN algorithm was validated using two FWD tests run on a long-term pavement performance section. Comparison between the backcalculated and measured results indicates that it should be possible to infer linear viscoelastic properties of AC layer as well as nonlinear elastic properties of unbound layers from FWD tests. 相似文献
7.
《International Journal of Pavement Engineering》2012,13(4):343-353
A fundamental study of a dynamic modulus for asphalt pavements was conducted using experimental tests and numerical simulations. The emphasis was on the loading frequency–vehicle speed relationships directly caused by the test results of vertical compressive stress pulse durations along the depth. A framework for determining the dynamic modulus is proposed based on the dynamic effects. It is shown that the proposed dynamic modulus is capable of predicting the asphalt pavement behaviour with varying vehicle speeds. The converting factor that can estimate the in situ dynamic modulus from the undamaged dynamic modulus is also proposed using a falling weight deflectometer modulus. Through comparisons with case histories, the maximum relative error of longitudinal strain is 50.4% with an undamaged dynamic modulus and 10.5% with an in situ dynamic modulus. The proposed methods with a converting factor are in agreement with the general trend observed by in situ measurements along the vehicle speeds. 相似文献
8.
《International Journal of Pavement Engineering》2012,13(5):600-614
ABSTRACTTo locally calibrate the Mechanistic-Empirical Pavement Design Guide (MEPDG) for the state of Wyoming, a comprehensive test programme and analyses were conducted. The field test programme included falling weight deflectometer tests, standard penetration tests, dynamic cone penetration tests and soil sampling. These field tests were conducted at 12 locations or 36 sites in the state of Wyoming. Subgrade soils collected from the field were characterised by a series of laboratory soil tests including resilient modulus tests, resistance-value tests and standard Proctor density tests. This test programme accumulated significant valuable soil data for local MEPDG calibrations. To efficiently store the results from the field and laboratory testing, an electronic WYOming MEPDG Database was developed using Microsoft® Access. Specific data or inputs requested by user are efficiently and easily sorted, filtered and queried using the database. Laboratory measured resilient modulus, resistance-values and standard Proctor properties of subgrade materials were used to develop both multivariate and univariate multi-regression models to accurately estimate resilient modulus for MEPDG Level 2 design inputs. Statistical parameters were used to effectively evaluate the performance of developed regression models. The resistance-value and optimum moisture content of subgrade soils were determined as important predictors in both models. The research outcomes facilitate the local calibration and implementation of the MEPDG. 相似文献
9.
《International Journal of Pavement Engineering》2012,13(4):417-424
AbstractSelection of optimal treatment strategy for a cracked asphalt pavement requires efficient evaluation of cracking. Pavement cracking severity was usually evaluated just by crack width in the past. In this paper, a novel method for extracting both crack type and crack width information in asphalt pavement with chemically stabilised base course from falling weight deflectometer (FWD) test data based on k-nearest neighbour (k-NN) pattern recognition was put forward. FWD field tests and core drilling tests were conducted at cracks on four typical expressways and a database with 215 deflection basins was established. Three feature sets were selected or extracted from each deflection basin as inputs. And, cracks were categorised into six classes based on crack type and crack width as target outputs. Results indicated that most cracks with high width level were thermal cracks and it was of great importance to consider both crack type and width in cracking evaluation in asphalt pavement with chemically stabilised base. Considering the classification accuracy and the convenience of test, crack was advised to be located between sensor S300 and sensor S600 in FWD field test. Deflection ratio feature set was recommended as inputs of the k-NN classifier. 相似文献
10.
Gary W. Chai Greg Kelly Tsu-Te Huang Sanaul H. Chowdhury Andrew Golding Sittampalan Manoharan 《International Journal of Pavement Engineering》2018,19(2):122-130
The primary objective of this paper is to present new methods in characterising flexible pavements that possess nonlinear subgrade behavior using deflection data from falling weight deflectometer (FWD). The two techniques to be introduced are Simplified Deflection Modeling and Deflection Ratio (DefR) approach. FWD deflection data can be modelled accurately using an exponential curve in a mathematical form of Y = K1 exp (?r/K2). K1 is equal to deflection at D0 in micron and K2 is the structural parameter at the respective sensor location. K2 parameter is found to have a direct relationship with the material constant, value of the subgrade and it is taken as a measurement of the nonlinearity of the pavement layer. As K2 increases and approaches 500, the pavement structure is observed to possess linear elastic behaviour. In the second method, the DefR is defined as the ratio of the FWD deflection of a sensor divided by the deflection of the preceding sensor. For pavements that exhibit nonlinear subgrade behavior, the DefR shows an increasing trend for FWD sensors located at 300mm and beyond. The two techniques have provided alternative approaches for modelling subgrade nonlinearity. 相似文献
11.
Alessandra Bianchini 《International Journal of Pavement Engineering》2014,15(9):831-839
A fundamental aspect in a pavement management system is the evaluation of the pavement structural condition and its capability in supporting the designated traffic. The nondestructive technique of the falling weight deflectometer and the layered elastic model are commonly used to identify pavement structural condition. The approach in this article is mechanistic–empirical, with the intent to correlate the strain at the bottom of the asphalt layer with the number of coverages to failure. Strains were computed through mathematical approximation of the deflection basin measured at failure. The proposed asphalt criterion showed the same trend of the subgrade strain criterion developed in conjunction with the reformulation of the California bearing ratio (CBR)-Beta design criteria. The approach provided encouraging results when compared with the other analyses in the development of the CBR-Beta criteria. The database was from the full-scale flexible pavement testing at the US Army Engineer Research and Development Center in Vicksburg, MS, USA. 相似文献
12.
Edward Offei Khaled Ksaibati Dick Apronti 《International Journal of Pavement Engineering》2016,17(6):517-527
Pavement widening can increase roadway capacity and improve safety, but results in a longitudinal joint between the existing and widened section that is susceptible to longitudinal pavement cracking. Previous research on construction methods focused on the pavement layer but this research looks at the effects of joint type on the base layer. Two base widening joint types, vertical and tapered, are commonly implemented by the Wyoming Department of Transportation. The objective of this study is to determine the most suitable base widening technique for durable pavement sections resistant to longitudinal cracking along the joint line. Field and laboratory evaluations were carried out on 28 existing pavement widening projects to determine the strength of the base layer as well as the occurrence and severity of longitudinal cracking. Results indicate that the tapered joint type has better strength in terms of the Dynamic Cone Penetrometer and Falling Weight Deflectometer analyses, less longitudinal cracking, and lower cost. 相似文献
13.
Omar Elbagalati Kevin Gaspard Zhongjie Zhang 《International Journal of Pavement Engineering》2018,19(1):1-8
Non-structural parameters such as surface distresses and ride quality have commonly been used as functional indicators in the treatment selection process. However, transportation agencies have considered in recent years implementing structural capacity indicators into their pavement management system (PMS) and decision-making processes. The objective of this study was to develop a structural condition index for Louisiana, known as the Structural Health Index (SHI), on a scale from 0 to 100 that describes the structural integrity of the pavement structure based on the backcalculated layer moduli of in-service pavements as predicted from FWD testing. Based on the developed methodology, the SHI is estimated by first backcalculating the layer moduli using a backcalculation software. Then, a sigmodal function is used to calculate the SHI. Evaluation and validation of the SHI was successful and demonstrated that the new index responded realistically to sections in poor and in good structural conditions. Furthermore, it was shown that the new index provided additional information that complements existing functional indices in PMS by successfully identifying structurally deficient sections. The implementation of the SHI into the LADOTD decision matrix is demonstrated. 相似文献
14.
《International Journal of Pavement Engineering》2012,13(4):364-373
This paper investigates the use of artificial neural networks (ANNs) and genetic algorithms to improve the accuracy of the prediction of subgrade resilient modulus (M r) based on soil index properties. Furthermore, it also examines the effect of the accuracy of the M r estimation on the mechanistic empirical pavement design guide (MEPDG) performance prediction. The results of this paper showed that the ANN models had much better prediction of the M r coefficients of subgrade soils than that of the regression models. In addition, the use of the genetic algorithms in the selection of the input variables of the ANN models enhanced the accuracy of the prediction of those models. The results of the MEPDG analyses indicated that the prediction model used to estimate the subgrade M r input value can have a significant effect on the predicted performance of pavements. Furthermore, those results showed that the use of ANN models yielded much more accurate pavement performance prediction than using regression models; in particular when genetic algorithms were used in developing those models. 相似文献
15.
《International Journal of Pavement Engineering》2012,13(10):906-918
This paper describes in situ measurement results and analysis of a deteriorating jointed concrete pavement supported on open-graded aggregate subbase that was subsequently treated with high-density polyurethane foam. The foam was injected under pressure into the subbase to improve support conditions, mitigate faulting and improve load transfer efficiency (LTE) at the joints. A variety of in situ tests were conducted to evaluate ride quality, pavement deflections under dynamic loading, LTE at joints and cracks, pavement surface elevation changes, and drainage and stiffness of the treated subbase layer. Testing on the pavement surface indicated statistically significant improvements near cracks after treatment with reduced peak deflections and higher LTE, but the pavement ride quality measurements did not show improvement. Tests performed on the foundation layer indicated that the construction process resulted in concentrated zones of foam in the subbase with low permeability, low stiffness and high shear strength, compared with untreated areas. 相似文献
16.
In perpetual pavements, damage from bottom-up cracking can be limited to the top surface lift through using a very thick surface layer or a binder-rich intermediate layer. This can be attained by maintaining tensile strains at the bottom of the hot-mix asphalt (HMA) layer below a certain value known as the fatigue endurance limit (FEL). This paper presents a method for estimating a strain-based FEL for flexible airfield pavements. The proposed method is based on the concept that a 50% reduction in HMA layer modulus would indicate initiation of fatigue cracking. Falling weight deflectometer (FWD) testing results, collected from National Airport Pavement Test Facility (NAPTF) flexible pavement sections, were analyzed to determine at which loading pass each section had a 50% reduction in HMA layer modulus (Nf50). NAPTF tensile strain data were also used to determine the tensile strain at Nf50 for each pavement section by averaging the peak tensile strains. The proposed approach was validated by comparing its results to those obtained using a common FEL estimation model known as the rate of dissipated energy change (RDEC) model. To further verify the results of the proposed approach, peak tensile strain was plotted vs. number of loading cycles for all sensors. Using these plots, the peak tensile strain at which the variability in the strain gauge data increased was used as an estimate of a possible FEL. The Nf50 tensile strains estimated using the proposed method were comparable to the values determined from RDEC and variability approaches. 相似文献
17.
《International Journal of Pavement Engineering》2012,13(6):431-444
Resilient modulus (M R) of subgrade soils is the elastic modulus based on the recoverable strain under repeated loads and depends on several factors such as soil properties, soil type and stress states. This paper presents the prediction equations to estimate M R from a set of soil physical properties for the unified soil classification system soil types namely coarse-grained and fine-grained subgrade soils. Data extracted from long-term pavement performance information management system database for 259 test specimens of reconstituted soil samples from 19 states in New England and nearby regions in the USA and two provinces in Canada were used in this study. Generalised constitutive model consisting bulk stress and octahedral shear stress was used to predict the M R of subgrade soils by developing equations for the regression coefficients (k-coefficients) in the constitutive model that relates them to various soil properties. Prediction models were developed by conducting multiple linear regression analysis using computer software SAS®. To verify the prediction models, a set of fresh laboratory M R tests were conducted on representative New England subgrade soils using AASHTO standards. The laboratory test results show that the developed models predict M R values fairly well for the soils with their properties values within the range used in developing the prediction models. 相似文献
18.
19.
《International Journal of Pavement Engineering》2012,13(3):171-182
This paper describes the use of artificial neural networks (ANNs) as pavement structural analysis tools for the rapid and accurate prediction of critical responses and deflection profiles of full-depth flexible pavements subjected to typical highway loadings. The ILLI-PAVE finite element program, extensively tested and validated for over three decades, was used as an advanced structural model for solving the critical responses of full-depth flexible pavements. Unlike the linear elastic layered theory commonly used in pavement layer backcalculation, nonlinear stress-dependent subgrade soil response models were used in the ILLI-PAVE program to account for the softening nature of fine-grained subgrade soils under increasing stress states. ANN models then trained with the results from the ILLI-PAVE solutions have been found to be viable alternatives. The trained forward calculation ANN models were capable of predicting asphalt tensile strains and subgrade compressive stresses/strains with low average absolute errors of those obtained directly from the ILLI-PAVE analyses. ANN backcalculation models developed in this study were also capable of successfully predicting the pavement layer moduli from the falling weight deflectometer (FWD) deflection basins and they may be used in the field for rapidly assessing the condition of pavement sections during the FWD testing. 相似文献
20.
Mona Nobakht Maryam S. Sakhaeifar David Newcomb Shane Underwood 《International Journal of Pavement Engineering》2018,19(8):675-684
A well-planned rehabilitation approach helps agencies to optimise the allocation of annual investment in pavement rehabilitation programs. Currently, many agencies are struggling with the selection of an optimal time-based and cost-effective rehabilitation solution to address the long-term needs of pavements. This study offers the use of a mechanistic-empirical methodology to develop a series of time-based rehabilitation strategies for high traffic volume flexible pavements located in Oklahoma. Six different pavement family groups are identified in the state, and comprehensive evaluation of existing pavements are conducted through analysis of falling weight deflectometer data and performance measures available in Oklahoma Pavement Management System database. The inadequacy of performance measures to fully characterise the condition of existing pavements are indicated, and damage factor determined from FWD data are suggested as trigger factor to select rehabilitation candidates. Three levels of rehabilitation activities including light, medium and heavy are considered as potential alternatives for rehabilitation candidates. A mechanistic-empirical methodology is employed to obtain an estimate of the performance of rehabilitation and extension in service lives of pavements. Also, an assessment output matrix is developed, which can be served as a supplemental tool to help the decision-makers in the highway agency with the rehabilitation related decision-making process. Cost-effectiveness of rehabilitation alternatives is determined through life cycle cost analysis, and three time-based renewal solutions are developed for pavement family groups that are in need of rehabilitation. 相似文献