The Mechanistic Empirical Pavement Design Guide (MEPDG) developed by the National Cooperative Highway Research Program (NCHRP) project 1-37A, is a very powerful tool for the design and analysis of pavements. The designer utilizes an iterative process to select design parameters and predict performance, if the performance is not acceptable they must change design parameters until an acceptable design is achieved. The design process has more than 100 input parameters across many areas, including, climatic conditions, material properties for each layer of the pavement, and information about the truck traffic anticipated. Many of these parameters are known to have insignificant influence on the predicted performance During the development of this procedure, input parameter sensitivity analysis varied a single input parameter while holding other parameters constant, which does not allow for the interaction between specific variables across the entire parameter space. A portion of this research identified a methodology of global sensitivity analysis of the procedure using random sampling techniques across the entire input parameter space. This analysis was used to select the most influential input parameters which could be used in a streamlined design process. This streamlined method has been developed using Multiple Adaptive Regression Splines (MARS) to develop predictive models derived from a series of actual pavement design solutions from the design software provided by NCHRP. Two different model structures have been developed, one being a series of models which predict pavement distress (rutting, fatigue cracking, faulting and IRI), the second being a forward solution to predict a pavement thickness given a desired level of distress. These thickness prediction models could be developed for any subset of MEPDG solutions desired, such as typical designs within a given state or climatic zone. These solutions could then be modeled with the MARS process to produce am “Efficient Design Solution” of pavement thickness and performance predictions. The procedure developed has the potential to significantly improve the efficiency of pavement designers by allowing them to look at many different design scenarios prior to selecting a design for final analysis.

Desde a implantação das primeiras obras, há indicações de que seus construtores já apresentavam conhecimentos acerca da influência da drenagem no desempenho dos pavimentos. Muitos países, onde os custos rodoviários são avaliados criteriosamente ao longo de toda a vida de serviço do pavimento, vêm desenvolvendo pesquisas objetivando a consideração dos efeitos prejudiciais da água em excesso no interior de sua estrutura. Métodos consagrados como, por exemplo, o da AASHTO, já consideram a influência da eficiência do sistema de drenagem no dimensionamento das estruturas de pavimentos. Neste trabalho, são apresentados um breve histórico e uma análise dos métodos de dimensionamento nacionais e estrangeiros, com vistas às considerações da influência do sistema de drenagem e da variação sazonal do teor de umidade no desempenho estrutural dos pavimentos. Fazendo-se uso do Falling Weight Defectometer, foi realizado levantamento deflectométrico em trecho experimental, com extensão aproximada de 900 m, direcionado para a avaliação da variação dos módulos resilientes das camadas e do comportamento estrutural diante da infiltração d\'água pela borda do pavimento. A partir dos dados obtidos no segmento experimental, pôde-se avaliar a magnitude desses parâmetros e assim efetuar, através de modelos analíticos que expressam os métodos de dimensionamento vigentes no país, a estimativa de redução da vida útil do pavimento analisado. Finalmente, propõe-se a introdução de um parâmetro de ajuste da espessura, denominado Fator de Ajuste de Drenagem, para consideração das condições adversas de drenagem no procedimento de dimensionamento de estruturas de pavimentos flexíveis preconizado pelo DNER. / Since the implementation of the first roads, there are indications that constructors already had knowledge concerning drainage influence in the pavement performance. Many countries, where highway administration costs are criteriously available along pavement lifetime, have been developing researches regarding considerations about harmful effects from excessive water in the pavement structure. Renowned methods such as AASHTO, already consider the influence of drainage system efficiency in the pavement structures design. In this work, brief historic and an analysis about national and foreign design methods are presented, taking into account considerations concerning influence of drainage system and seasonal variations of moisture content in the structural pavement performance. Employing the Falling Weight Deflectometer, deflection measurements were carried out in a test section, about 900 m long, in order to evaluate the resilient modulus layers and the structural behavior variations due to water infiltration from pavement edge. From experimental sections data obtained, it was possible to evaluate the magnitude of these parameters and then realize, through analytical models that represent the actual national design methods, the reduction estimate of evaluated pavement lifetime. Finally, this work propose the introduction of a thickness adjustment parameter, called Drainage Adjustment Factor, to consider the adverse drainage conditions in the flexible pavement structure design procedure advocated by DNER.

Porous asphalt pavements offer an alternative technology for stormwater management. A porous asphalt pavement differs from traditional asphalt pavement designs in that the structure permits fluids to pass freely through it, reducing or controlling the amount of run-off from the surrounding area. By allowing precipitation and run-off to flow through the structure, this pavement type functions as an additional stormwater management technique. The overall benefits of porous asphalt pavements may include both environmental and safety benefits including improved stormwater management, improved skid resistance, reduction of spray to drivers and pedestrians, as well as a potential for noise reduction. With increasing environmental awareness and an evolving paradigm shift in stormwater management techniques, this research aims to provide guidance for Canadian engineers, contractors, and government agencies on the design of porous asphalt pavement structures. One of the keys to the success of this pavement type is in the design of the asphalt mix. The air void percentage, which is ultimately related to the effectiveness of the pavement to adequately control the runoff, is a critical component of the mix. However, special consideration is required in order to obtain higher air void percentages while maintaining strength and durability within a cold climate. The objectives of this study were to evaluate several laboratory porous asphalt mix designs for durability and strength in cold climate conditions. The porous asphalt mixes consisted of a porous asphalt Superpave mix design method whereby the asphalt binder type was varied. Performance testing of the porous asphalt including draindown susceptibility, moisture-induced damage susceptibility, dynamic modulus, and permeability testing were completed. Based on the preliminary laboratory results, an optimal porous asphalt mix was recommended for use in a Canadian climate. Initial design guidelines for porous asphalt were provided based on preliminary findings and hydrological analysis.

There is a growing interest for the use of mechanistic procedures and analytical methods in the design and evaluation of pavement structure rather than empirical design procedures. The mechanistic procedures rely on predicting pavement response under traffic and environmental loading (i.e., stress, strain, and deflection) and relating these responses to pavement field performance. A research program has been developed at the Center for Pavement and Transportation Technology (CPATT) test track to investigate the impact of traffic and environmental parameters on flexible pavement response. This unique facility, located in a climate with seasonal freeze/thaw events, is equipped with an internet accessible data acquisition system capable of reading and recording sensors using a high sampling rate. A series of controlled loading tests were performed to investigate pavement dynamic response due to various loading configurations. Environmental factors and pavement performance were monitored over a two-year period. Analyses were performed using the two dimensional program MichPave to predict pavement responses. The dynamic modulus test was chosen to determine viscoelastic properties of Hot Mix Asphalt (HMA) material. A three-step procedure was implemented to simplify the incorporation of laboratory determined viscoelastic properties of HMA into the finite element (FE) model. The FE model predictions were compared with field measured pavement response. Field test results showed that pavement fully recovers after each wheel pass. Wheel wander and asphalt mid-depth temperature changes were found to have significant impact on asphalt longitudinal strain. Wheel wander of 16 cm reduced asphalt longitudinal strains by 36 percent and daily temperature fluctuations can double the asphalt longitudinal strain. Results from laboratory dynamic modulus tests found that Hot Laid 3 (HL3) dynamic modulus is an exponential function of the test temperature when loading frequency is constant, and that the HL3 dynamic modulus is a non-linear function of the loading frequency when the test temperature is constant. Results from field controlled wheel load tests found that HL3 asphalt longitudinal strain is an exponential function of asphalt mid-depth temperature when the truck speed and wheel loading are constant. This indicated that the laboratory measured dynamic modulus is inversely proportional to the field measured asphalt longitudinal strain. Results from MichPave finite element program demonstrated that a good agreement between field measured asphalt longitudinal strain and MichPave prediction exists when field represented dynamic modulus is used as HMA properties. Results from environmental monitoring found that soil moisture content and subgrade resilient modulus changes in the pavement structure have a strong correlation and can be divided into three distinct Seasonal Zones. Temperature data showed that the pavement structure went through several freeze-thaw cycles during the winter months. Daily asphalt longitudinal strain fluctuations were found to be correlated with daily temperature changes and asphalt longitudinal strain fluctuations as high as 650m/m were recorded. The accumulation of irrecoverable asphalt longitudinal strain was observed during spring and summer months and irrecoverable asphalt longitudinal strain as high as 2338m/m was recorded.

Porous asphalt pavements offer an alternative technology for stormwater management. A porous asphalt pavement differs from traditional asphalt pavement designs in that the structure permits fluids to pass freely through it, reducing or controlling the amount of run-off from the surrounding area. By allowing precipitation and run-off to flow through the structure, this pavement type functions as an additional stormwater management technique. The overall benefits of porous asphalt pavements may include both environmental and safety benefits including improved stormwater management, improved skid resistance, reduction of spray to drivers and pedestrians, as well as a potential for noise reduction. With increasing environmental awareness and an evolving paradigm shift in stormwater management techniques, this research aims to provide guidance for Canadian engineers, contractors, and government agencies on the design of porous asphalt pavement structures. One of the keys to the success of this pavement type is in the design of the asphalt mix. The air void percentage, which is ultimately related to the effectiveness of the pavement to adequately control the runoff, is a critical component of the mix. However, special consideration is required in order to obtain higher air void percentages while maintaining strength and durability within a cold climate. The objectives of this study were to evaluate several laboratory porous asphalt mix designs for durability and strength in cold climate conditions. The porous asphalt mixes consisted of a porous asphalt Superpave mix design method whereby the asphalt binder type was varied. Performance testing of the porous asphalt including draindown susceptibility, moisture-induced damage susceptibility, dynamic modulus, and permeability testing were completed. Based on the preliminary laboratory results, an optimal porous asphalt mix was recommended for use in a Canadian climate. Initial design guidelines for porous asphalt were provided based on preliminary findings and hydrological analysis.

There is a growing interest for the use of mechanistic procedures and analytical methods in the design and evaluation of pavement structure rather than empirical design procedures. The mechanistic procedures rely on predicting pavement response under traffic and environmental loading (i.e., stress, strain, and deflection) and relating these responses to pavement field performance. A research program has been developed at the Center for Pavement and Transportation Technology (CPATT) test track to investigate the impact of traffic and environmental parameters on flexible pavement response. This unique facility, located in a climate with seasonal freeze/thaw events, is equipped with an internet accessible data acquisition system capable of reading and recording sensors using a high sampling rate. A series of controlled loading tests were performed to investigate pavement dynamic response due to various loading configurations. Environmental factors and pavement performance were monitored over a two-year period. Analyses were performed using the two dimensional program MichPave to predict pavement responses. The dynamic modulus test was chosen to determine viscoelastic properties of Hot Mix Asphalt (HMA) material. A three-step procedure was implemented to simplify the incorporation of laboratory determined viscoelastic properties of HMA into the finite element (FE) model. The FE model predictions were compared with field measured pavement response. Field test results showed that pavement fully recovers after each wheel pass. Wheel wander and asphalt mid-depth temperature changes were found to have significant impact on asphalt longitudinal strain. Wheel wander of 16 cm reduced asphalt longitudinal strains by 36 percent and daily temperature fluctuations can double the asphalt longitudinal strain. Results from laboratory dynamic modulus tests found that Hot Laid 3 (HL3) dynamic modulus is an exponential function of the test temperature when loading frequency is constant, and that the HL3 dynamic modulus is a non-linear function of the loading frequency when the test temperature is constant. Results from field controlled wheel load tests found that HL3 asphalt longitudinal strain is an exponential function of asphalt mid-depth temperature when the truck speed and wheel loading are constant. This indicated that the laboratory measured dynamic modulus is inversely proportional to the field measured asphalt longitudinal strain. Results from MichPave finite element program demonstrated that a good agreement between field measured asphalt longitudinal strain and MichPave prediction exists when field represented dynamic modulus is used as HMA properties. Results from environmental monitoring found that soil moisture content and subgrade resilient modulus changes in the pavement structure have a strong correlation and can be divided into three distinct Seasonal Zones. Temperature data showed that the pavement structure went through several freeze-thaw cycles during the winter months. Daily asphalt longitudinal strain fluctuations were found to be correlated with daily temperature changes and asphalt longitudinal strain fluctuations as high as 650m/m were recorded. The accumulation of irrecoverable asphalt longitudinal strain was observed during spring and summer months and irrecoverable asphalt longitudinal strain as high as 2338m/m was recorded.

Pavement Management Systems (PMS) are widely used by transportation agencies to maintain safe, durable and economic road networks. PMS prioritize the maintenance and rehabilitation of pavement sections by evaluating pavement performance at the network level. There are many PMS software packages that have been developed over the past decades for provincial/state road agencies. However, sometimes due to lack of budget and experience, adopting the existing PMS for a road agency is not cost effective. Thus, it is important to introduce a simple, effective, and affordable PMS for a local agency and municipality. This research is carried out in partnership between the City of Markham and the Centre for Pavement and Transportation Technology (CPATT) located at the University of Waterloo. For the purpose of developing a PMS for local agencies, an extensive literature review on PMS components was carried out, with emphasizing data inventory, data collection, and performance evaluation. In addition, the literature review also concentrated on the overall pavement condition assessment. In July 2011, a study on “Evaluation of Pavement Distress Measurement Survey” was conducted as a part of this research and was distributed to cities and municipalities across Canada. The study focused on the current state-of-the-practice in pavement distress and condition evaluation methods used by local agencies to compare the results from the literature review. The components of the proposed PMS framework are also developed based on the literature review with some modifications and technical requirements. The City of Markham is selected as a case study, since it represents a local agency and provides all the data, to illustrate the validation of the proposed PMS framework.

The research presented in this thesis covers the development, calibration and verification of two thin surfaced unbound granular pavement models: one model to predict the response of a pavement to loading by the monotonic application of a single load event (Response model) and the other model to predict the accumulation of permanent deformation of the pavement when it is subjected to a large number of load applications (Performance model). The response model was developed using the finite element method and used an anisotropic stress dependent stiffness model to represent the granular and subgrade materials. The models were verified with an extensive set of stress, strain and surface deflection measurements collected at the CAPTIF facility. The calibrated models were able to predict the subsurface response of the pavement to a range of dual tyre and FWD load levels (23-72 kN). It was found that the measured stress and strain response of the pavement was different under the two loading mechanisms. It was also found that a particular response at a point in the pavement was linear with respect to load. The performance model was based on similarities observed in the performance of granular materials in both laboratory and full-scale experiments. When the specimen or pavement was showing a steady state response, it was found that the rate of accumulation of permanent deformation was related to the resilient strain. This relationship was then used to predict the deformation of CAPTIF pavements based on the outputs from the response model. The application of laboratory derived models required the use of shift functions to be able to be successfully used in replicating field measurements, this was expected given the differences in boundary conditions and loading mechanisms for the laboratory and field systems.

Pavement Management Systems (PMS) are widely used by transportation agencies to maintain safe, durable and economic road networks. PMS prioritize the maintenance and rehabilitation of pavement sections by evaluating pavement performance at the network level. There are many PMS software packages that have been developed over the past decades for provincial/state road agencies. However, sometimes due to lack of budget and experience, adopting the existing PMS for a road agency is not cost effective. Thus, it is important to introduce a simple, effective, and affordable PMS for a local agency and municipality. This research is carried out in partnership between the City of Markham and the Centre for Pavement and Transportation Technology (CPATT) located at the University of Waterloo. For the purpose of developing a PMS for local agencies, an extensive literature review on PMS components was carried out, with emphasizing data inventory, data collection, and performance evaluation. In addition, the literature review also concentrated on the overall pavement condition assessment. In July 2011, a study on “Evaluation of Pavement Distress Measurement Survey” was conducted as a part of this research and was distributed to cities and municipalities across Canada. The study focused on the current state-of-the-practice in pavement distress and condition evaluation methods used by local agencies to compare the results from the literature review. The components of the proposed PMS framework are also developed based on the literature review with some modifications and technical requirements. The City of Markham is selected as a case study, since it represents a local agency and provides all the data, to illustrate the validation of the proposed PMS framework.

abstract: Recent research efforts have been directed to improve the quality of pavement design procedures by considering the transient nature of soil properties due to environmental and aging effects on pavement performance. The main purpose of this research study was to investigate the existence of subgrade soil moisture changes that may have arisen due to thermal and hydraulic gradients at the Atlantic City NAPTF and to evaluate their effect on the material stiffness and the California Bearing Ratio (CBR) strength parameter of the clay subgrade materials. Laboratory data showed that at the same water content, matric suction decreases with increasing temperature; and at the same suction, hydraulic conductivity increases with increasing temperature. Models developed, together with moisture/temperature data collected from 30 sensors installed in the test facility, yielded a maximum variation of suction in field of 155 psi and changes in hydraulic conductivity from 2.9E-9 m/s at 100% saturation to 8.1E-12 at 93% saturation. The maximum variation in temperature was found to be 20.8oC at the shallower depth and decreased with depth; while a maximum variation in moisture content was found to be 3.7% for Dupont clay and 4.4% for County clay. Models developed that predicts CBR as a function of dry density and moisture content yielded a maximum variation of CBR of 2.4 for Dupont clay and 2.9 for County clay. Additionally, models were developed relating the temperature with the bulk stress and octahedral stress applied on the subgrade for dual gear, dual tandem and triple tandem gear types for different tire loads. It was found that as the temperature increases the stresses increase. A Modified Cary and Zapata model was used for predicting the resilient modulus(Mr) of the subgrade. Using the models developed and the temperature/moisture changes observed in the field, the variation of suction, bulk and octahedral stresses were estimated, along with the resilient modulus for three different gear types. Results indicated that changes in Mr as large as 9 ksi occur in the soils studied due to the combined effect of external loads and environmental condition changes. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2017