No description available.

The purpose of a geotextile separator beneath a granular base, or subbase in a flexible pavement system is to prevent the road aggregate and the underlying subgrade from intermixing. It has been hypothesized that in the absence of a geotextile, intermixing between base course aggregate and soft subgrade occurs. Nine heavily instrumented flexible pavement test sections were built in Bedford County Virginia to investigate the benefits of geosynthetic stabilization in flexible pavements. Three groups of different base course thicknesses (100, 150 and 200mm) test sections were constructed with either geotextile or geogrid stabilization or no stabilization. Woven geotextile was used in sections 2, 5 and 8. Geogrids were used in sections 3, 6 and 9, and sections 1, 4 and 7 were controls. Six Falling weight deflectometer (FWD) tests were performed on all the nine sections over 30 months. The nine sections were subjected to at least 5 load drops with wide loading range each time. The measured deflections were analyzed using the MODULUS back-calculation program to determine layer moduli. The measured deflections were used together with elastic, viscoelastic and the MODULUS program to determine the extent of intermixing at base-subgrade interface. The study concluded that a transition layer would develop when a separator is absent, especially in the weak sections (designed to fail in three years). Other measurements such as in-situ stresses, rut depth, and subsurface profiling (using ground penetrating radar) support the conclusion of the development of a transition layer. / Master of Science

For the past three decades, geosynthetics have been recognized as materials that can significantly improve the performance of pavements on weak subgrade. Pavements exhibit non-linear elasto-plastic behavior. The addition of geosynthetics is undoubtedly beneficial. This being said, researchers have concentrated more on lower life cycle cost and high benefit-cost ratio whereas much less attention has been given to the complex behavior of the reinforced pavement system. Comprehension of the short-term and long-term field performance of reinforced pavements under continued traffic and cyclic environmental loading has remained unexplored. There is empirical evidence indicating quantitative benefits of reinforced versus unreinforced pavement structure. However, quantification of the relative benefits of different types of reinforcement like geogrids and geotextiles lacks information. Further, evaluation of the benefits and comparison of chemical stabilization in the form of lime treatment with mechanical stabilization in the form of reinforcement for pavements on soft soils has received lack of attention. In view of this, full-scale instrumented reinforced and lime treated pavement sections with different schemes were studied. Regular Falling Weight Deflectometer (FWD) testing was conducted in a Farm-to-Market Road, in Grimes County, Texas. Three different geosynthetic products were used for base reinforcement and lime treatment was used for subbase stabilization. Deflection measurements for 9 field trips in 3.5 years were evaluated. Modified deflection basin parameters (DBPs) were defined to typically identify layer properties and were used to measure the relative damage to the base, subbase and subgrade for different sections. A modified Base Damage Index (BDI) and a modified Base Curvature Index (BCI) were defined as a part of this study to capture the benefit of reinforced base and lime stabilized subbase respectively. The variation in the DBPs over three periods of wetting and drying along with explanation of the observed trends forms a part of this research. In addition, a number of condition surveys were performed, during 3 years, to visually identify distresses in various sections. A unique distress quantification technique was developed for measuring deterioration of the pavement sections in terms of the observed distresses and FWD measurements. With this, an index of pavement performance was developed. Thus, the FWD deflection data analyses complemented by visual observation, reveals important information on performance of different geosynthetics with the same base course. Analysis of the field performance of the multiple experimental sections throws light on the relative merits of base reinforcement against lime stabilization. / text

In the mechanistic design approach, which has already been started to utilize in several countries, the variations in material properties are better taken into account based on fundemental engineering principles. Resilient modulus is the most important material property that is used in the mechanistic design since it describes the true martial performance of unbound pavement layers under traffic loading. In this thesis, the objective is to determine the resilient modulus, used in the mechanistic design of pavement structures, for the unbound material types used in Turkey and develop linear and nonlinear prediction models to determine resilient response of unbound layers based on soil index properties, California Bearing Ratio (CBR) and Light Falling Weight Deflectometer (LFWD) test results. Application of genetic algorithm and curve shifting methodology to estimate design resilient modulus at various stress states is also investigated using the test results for finegrained soils. Resilient modulus estimation for a constant stress state based on genetic algorithm and curve shifting methodolgy is quite promising for fine-grained soils since nonlinear constitutive models do not have the capability of representing resilient responses under different conditions. Furthermore, tree-based modeling is discussed as an alternative way to develop resilient modulus prediction models. The outcome of the study will be a basis for the performance based design specifications of flexible pavements.

Submitted by Lucienne Costa (lucienneferreira@ufcg.edu.br) on 2018-04-13T18:16:49Z No. of bitstreams: 1 MAURO HENRIQUE ALVES NASCIMENTO – DISSERTAÇÃO (PPGECA) 2017.pdf: 22942682 bytes, checksum: d52bbbcac224ea9695c0dd3c9ffc12d1 (MD5) / Made available in DSpace on 2018-04-13T18:16:49Z (GMT). No. of bitstreams: 1 MAURO HENRIQUE ALVES NASCIMENTO – DISSERTAÇÃO (PPGECA) 2017.pdf: 22942682 bytes, checksum: d52bbbcac224ea9695c0dd3c9ffc12d1 (MD5) Previous issue date: 2017-06-09 / Com a finalidade de sanar as degradações do pavimento, devem-se realizar estudos avaliativos das condições estruturais, objetivando identificar as possíveis causas dos defeitos e sobretudo fornecer subsídios, sobre quais medidas corretivas devem ser adotadas para a restauração das condições adequadas e aceitáveis do pavimento. Diante destas circunstâncias, o presente trabalho tem como objetivo identificar as possíveis causas das ocorrências dos defeitos parabólicos observados na superfície dos pavimentos flexíveis das pistas de pouso e decolagem e de taxiamento do Aeroporto Internacional de Natal. Para isso, realizou-se uma avaliação estrutural não destrutiva, por meio do levantamento deflectométrico com o Falling Weight Deflectometer (FWD), o qual foi realizado em toda a extensão das pistas e em diversas faixas de aquisição de dados. Com o FWD obteve-se as bacias de deflexões que possibilitaram por processo de retroanálise, por meio do software BAKFAA 2.0, caracterizar o comportamento resiliente in situ das camadas do pavimento. Com o software ELSYM5 realizou-se a análise empírico-mecanística, para verificar os níveis de tensões cisalhantes atuantes nas diversas profundidades das camadas do pavimento, inclusive na interface de ligação entre as camadas asfálticas. Também foram realizados ensaios laboratoriais de caracterização das propriedades mecânicas, tais como: módulo de resiliência, resistência a tração indireta e o ensaio de Leutner shear Test. Concluiu-se que os defeitos observados na superfície das pistas enquadravam-se na série de defeitos classificados de escorregamento do revestimento asfáltico, ou Slippage, e que os fatores que culminaram na ocorrência destes defeitos relacionam-se com a baixa aderência da interface de ligação e com a incompatibilidade de rigidez entre as camadas adjacentes de mistura asfálticas. / In order to remedy pavement degradation, evaluation studies of the structural conditions should be carried out to identify the possible causes of the defects and, above all, provide information on which corrective measures should be taken to restore adequat and acceptable conditions of the pavement. In view of these circumstances, the present work has the objective of identifying the possible causes of parabolic defects seen in the surface of the flexible pavements of the landing and take - off runways and taxiways of Natal International Airport runway. For this, a non-destructive structural evaluation was carried out by means of the deflectometric survey with the Falling Weight Deflectometer (FWD), which was carried out along the whole length of the tracks and in several ranges of data acquisition. With the FWD, the deflection basins were obtained, which enabled the BAKFAA 2.0 software to characterize the in situ resilient behavior of the pavement layers by means of a retro-analysis process. With the ELSYM5 software, the empirical-mechanistic analysis was performed to verify the levels of shear stresses at different depths of the pavement layers, including the interface between the asphalt layers. Furthermore, laboratory characterization of mechanical properties such as: resilience modulus, tensile strength and Leutner shear test were carried out. It is concluded that the defects observed on the runway surface fit into the series of defects classified as slippage of the asphalt coating, or Slippage, and that the factors that culminated in the occurrence of these defects are related to the low adhesion of the interface and With the incompatibility of stiffness between the adjacent layers of asphalt mixtures.

Submitted by Geyciane Santos (geyciane_thamires@hotmail.com) on 2015-09-30T14:23:40Z No. of bitstreams: 1 Dissertação - Washington Luiz Pinto Filho.pdf: 8211076 bytes, checksum: 5b0146ee71fe71f4ffea30a9fca0f822 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-10-02T20:44:54Z (GMT) No. of bitstreams: 1 Dissertação - Washington Luiz Pinto Filho.pdf: 8211076 bytes, checksum: 5b0146ee71fe71f4ffea30a9fca0f822 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-10-06T19:53:40Z (GMT) No. of bitstreams: 1 Dissertação - Washington Luiz Pinto Filho.pdf: 8211076 bytes, checksum: 5b0146ee71fe71f4ffea30a9fca0f822 (MD5) / Made available in DSpace on 2015-10-06T19:53:40Z (GMT). No. of bitstreams: 1 Dissertação - Washington Luiz Pinto Filho.pdf: 8211076 bytes, checksum: 5b0146ee71fe71f4ffea30a9fca0f822 (MD5) Previous issue date: 2013-11-29 / Não informada / The city of Manaus has the highest average growth rates of the fleet, according to the DENATRAN. Over the past 10 years, the fleet of cars rose from 124,840 (2003) to 297,473 cars (2013) and 3,179 buses (2003) to 7,398 buses (2013). This equates to a 138% increase. Moreover, although, according to DENATRAN in 2003, Manaus was 220,816 vehicles. In 2013, Manaus already has 551,455 registered vehicles in its municipal fleet, which equates to an increase of almost 150%. As a result of this growth, the city roads are presented with its ability to flow and dead, visually, with their decks completely deformed. In this sense, we tried to carry this research, a structural evaluation of pavements of the main streets of the town (Av. Constantino Nery, Avenida Djalma Batista, Recife Av, Av and Av Efigênio Sales Paraíba), employing the technique FWD (Falling Weight Deflectometer) in the diagnosis of the pavement structures of these pathways. The results showed that the structures of those decks still have the condition to withstand the demands of traffic load applied to them, since their structural quality obtained by the mentioned technique, presented in good condition, according to the floors they presented deflections smaller than the allowed maximum, and radii of curvature much greater than 100 m. In addition, analysis was performed of the safety of the coating with respect to tire-pavement grip, which presented values for microtexture and macrotexture well outside the ranges recommended by the standards. / A cidade de Manaus apresenta uma das maiores taxas de crescimento médio da frota de veículos, segundo dados do DENATRAN. Nos últimos 10 anos, a frota de automóveis aumentou de 124.840 (2003) para 297.473 automóveis (2013) e 3.179 ônibus (2003) para 7.398 ônibus (2013). Isto equivale a um aumento de 138 %. Ademais, ainda, segundo o DENATRAN, em 2003, Manaus tinha 220.816 veículos. Em 2013, Manaus já possui 551.455 veículos registrados na sua frota municipal, o que equivale a um aumento de quase 150 %. Como consequência deste crescimento, as vias da cidade apresentam-se com sua capacidade de fluxo inoperante e, visualmente, com seus pavimentos totalmente deformados. Neste sentido, procurou-se realizar, nesta pesquisa, uma avaliação estrutural dos pavimentos das principais vias da cidade (Av. Constantino Nery, Av. Djalma Batista, Av. Recife, Av. Paraíba e Av. Efigênio Sales), empregando a técnica FWD (Falling Weight Deflectometer) no diagnóstico das estruturas dos pavimentos das referidas vias. Os resultados obtidos mostraram que as estruturas daqueles pavimentos ainda apresentam a condição de suportar as solicitações de carga de tráfego a elas aplicadas, visto que sua qualidade estrutural, obtida pela técnica mencionada, apresentou-se em boas condições, em função dos pavimentos terem apresentado deflexões máximas inferiores às admissíveis, bem como raios de curvatura muito superiores a 100 m. Como complemento à análise estrutural, realizou-se análise das condições funcionais do revestimento com relação à aderência pneu-pavimento, a qual apresentou valores para microtextura e macrotextura bem fora dos intervalos recomendados pelas normas.

When evaluating low volume roads (LVRs), structural capacity emphasis is minimal since deterioration typically results from environmental factors. However, in cases where LVR’s experience rapidly increased traffic loading, structural condition becomes important. The research objective was to determine whether the Light Weight Deflectometer (LWD) can be used as a structural evaluation tool for LVRs in the aforementioned conditions. This study explored the capability of LWD equipment in evaluating major factors that influence flexible pavement structural capacity: load induced deterioration, soil moisture, and asphalt temperature. Falling Weight Deflectometer (FWD) and LWD tests were performed to measure pavement structural condition. LWD was shown applicable for LVRs experiencing accelerated traffic. The LWD is portable and efficient for LVRs when high rut depths are permitted. The LWD and FWD produced similar trends. The LWD, based on this thesis, can be recommended for use in lieu of FWD to assess structural condition of LVRs for rapidly increased traffic loading.

No description available.

No description available.

A Rolling Dynamic Deflectometer (RDD) is a nondestructive testing device for determining continuous deflection profiles of pavements. Theses deflection profiles can be used more effectively when combined with other data such as pavement thickness, variability in moisture and other subsurface conditions, void detection and pavement right-of-way conditions. Therefore, a new, multi-function pavement testing device has been developed by a joint effort between the Texas Department of Transportation (TxDOT), the Center for Transportation Research (CTR) at the University of Texas at Austin (UT) and the Texas A&M Transportation Institute (TTI) at Texas A&M University. This new device is called the Total Pavement Acceptance Device (TPAD). The objective of TPAD testing is to nondestructively and nonintrusively investigate the structural adequacy of the total pavement system. The multiple functions of the TPAD presently include the following measurement capabilities: (1) rolling dynamic deflectometer (RDD), (2) ground penetrating radar (GPR), (3) global positioning (GPS), (4) pavement surface temperature, (5) digital video imaging of pavement and right-of-way conditions and (6) longitudinal survey offsets from known points through distance measurement (DMI). The TPAD is currently designed to perform continuous measurements at speeds around 2 to 3 mph. The effort in this dissertation is directed at: (1) developing the fourth-generation rolling sensors for faster testing speeds with the TPAD, (2) developing the Jointed Concrete Pavement (JCP) testbed with known and well-documented conditions (3) developing and evaluating the TPAD mobile platform, (4) evaluating the performance of the fourth-generation rolling sensors and refining a field calibration procedure and (5) studying the influence of the longitudinal and transverse joints in Jointed Concrete Pavement on TPAD deflection profile measurements. The first part involved the study of previous research and preliminary testing using the second-generation rolling sensor. Key benefits of the fourth-generation rolling sensor are: (1) reduced rolling noise during the testing, (2) higher signal-to-noise ratio (SNR), and (3) better tracking of the sensor. The second part of this work involved the development of the JCP testbed at the Texas Department of Transportation (TxDOT), Flight Services Facility (FSF) adjacent to the Austin-Bergstrom International Airport (ABIA). The JCP testbed was developed to establish a pavement facility with known and well-documented conditions for use in future research dealing with rigid pavement testing. The third part of this work involved the acceptance testing of the TPAD mobile platform for the RDD deflection measurements. The mobile platform was the one of the key components to develop the new moving pavement testing device. The TPAD mobile platform was developed by modifying a small, off-road vibroseies built by Industrial Vehicle International, Inc. (IVI). Acceptance testing of each of the following components was performed: (1) automated speed control, (2) static loading system and (3) dynamic loading system. The fourth part of this work involved the TPAD deflection measurements at the testbed at the TxDOT FSF. The deflection profiles using the fourth-generation rolling sensors and TPAD were performed at the established testbed. During the performance evaluation testing, the new sensor positioning, towing and raising/lowering system was developed and installed in the TPAD. The fifth part of this study involved the deflection measurement using the TPAD-RDD system on the jointed concrete pavement. This study includes the repeatability of the TPAD deflection measurements, the influence of the proximity to the longitudinal and transverse joints in JCP on TPAD deflection measurements, deflection measurements under different pavement surface temperature, the characteristic of the TPAD-RDD deflections and the comparison between the Falling Weight Deflectometer and TPAD deflection measurement testing. / text