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.

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.

Analizuojama asfalto dangos konstrukcijos elgsena Lietuvos klimato sąlygomis, įvertinant temperatūros ir drėgnio, kaip vienų iš svarbiausių klimato veiksnių, įtaką kelio asfalto dangos konstrukcijos stipriui. Pateikta krintančio svorio deflektometro matavimo metodikų apžvalga kitose šalyse. Atlikta temperatūros ir drėgnio kiekvienos dienos pokyčių analizė, įvertinant jų įtaką dangos konstrukcijai. Nustatyta kelio dangos stiprio ir Eo modulio priklausomybė nuo dangos temperatūros, matuojant kelio dangos įlinkius krintančio svorio deflektometru. Kai asfalto dangos stipris matuojamas skirtingu metų laiku ar įvairiu paros metu, tai Eo modulio reikšmės turi būti redukuojamos priimtai standartinei temperatūrai. Eksperimentiniame asfalto dangų konstrukcijų ruože atliktu tyrimu patikslintas temperatūrinis redukcijos koeficientas, kuris leidžia krintančio svorio deflektometru nustatytas asfalto dangos sluoksnių Eo modulio vertes redukuoti standartinei +20 °C temperatūrai. / This final master thesis performs asphalt pavement structural behavior of the Lithuanian climate conditions, taking into account the temperature and moisture, as one of the most important climatic factors that influence the road asphalt pavement structural strength. The Falling Weight Deflectometer (FWD) measurement methods used in other countries are presented. The temperature and moisture changes in the day are analysed, evaluating their impact on pavement design. The strength of asphalt pavement layers, as well as Eo modulus values, measured using the falling weight deflectometer, strongly depend on the pavement temperature. When we use deflectometer for measuring asphalt pavement strength at different environmental conditions and in different season, the values of Eo modulus should be reduced to the assumed standard temperature. So during this research at the experimental asphalt pavement structure the temperature correction factor was revised. The use of this factor enables to adjust the Eo modulus values of asphalt pavement layers measured by the Falling Weight Deflectometer to the standard temperature of +20 °C.

The bearing capacity of a road decreases greatly during spring thaw, when the previously frozen road begins to thaw. The extent of this decrease can be evaluated by making Falling Weight Deflectomter (FWD) measurements on the road, measuring the deflection of the road when an impact load is applied to it. The bearing capacity of the road can then be evaluated by backcalculating the layer modules with backcalculation programs, or through more simple calculations based on the deflection basin indices. Both analyses were carried out in this thesis with data from FWD measurements which were carried out on county road Lv 126 in Southern Sweden during the year 2010. The temperature and moisture content of the road were monitored during the same time. The aim with the thesis was to compare the two ways of analyses, and to find out if there is some relationship between them and the measured environmental data. The results showed that the base course layer and subbase decreased in stiffness during spring thaw about 50% while the decrease in the subgrade was 20%, compared to the backcalculated summer and autumn value. The results of the simple calculations from the deflection basin indices were well comparable to the backcalculation results. By comparing the backcalculated stiffness values to the moisture content measurements it was stated that the stiffness decreased as the moisture content increased.

This thesis investigates the application of In-Situ Recycling and provides guidelines for localities to aid in the selection of recycling methods, as well as documents a local government's experience with Cold In-Place Recycling. The recycling methods discussed in this study include Cold In-Place Recycling (CIR), Hot In-Place Recycling (HIR), and Full Depth Reclamation (FDR). These methods are performed onsite and in-place in a continuous process of milling, mixing, and placement. The In-Situ Recycling guidelines include suggestions based on: traffic characteristics, existing road condition, distress types, road access, local climate, road geometry, and other road characteristics. The guidelines are based on information from sources including NCHRP Synthesis 421, American Recycling and Reclamation Association (ARRA), FHWA, and state agencies with recycling experience. This study also resulted in documenting obstacles that localities may face when in-situ recycling, as well as the impact of limited experience with recycling. The study also evaluated the construction of Cold In-Place Recycled pavement sections in Christiansburg, VA, using Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR). Additionally, using the FWD and GPR data, alternate recycled designs were proposed in addition to a cost comparison to a conventional design. / Master of Science

The structural behaviour of pavements in cold regions can considerably be affected by seasonal variation in environmental factors such as temperature and moisture content. Along with the destructive effect of heavy traffic loads, climatic and environmental factors can considerably contribute to pavement deterioration. These factors can influence the structural and functional capacity of the pavement structures which, as a result, can trigger and accelerate pavement deterioration mechanisms. Studies on the influence of variation of the environmental factors on the response and behaviour of pavement materials have shown that proper consideration to these factors must be given in realistic pavement design and analysis. In flexible pavement structures, particularly with a thin hot mix asphalt (HMA) layer, unbound materials and subgrade soil largely contribute to the overall structural behaviour of the pavement system. In unbound materials, moisture content and its variation can significantly affect pavement layer stiffness and permanent deformation characteristics. Therefore, the moisture condition of pavements and its influence on the mechanical behaviour of pavement materials has been of interest among the pavement research community. A proper understanding of moisture transformation in pavement systems and its effects on pavement performance are important for mechanistic pavement design. The present summary of this doctoral thesis is based on four main parts. The first part of the thesis covers field measurements and findings from a test section along county road 126 in southern Sweden and consists of two journal papers (paper I and II) tackling different aspects of the research topic. This test section is located in a relatively wet ground condition and consists of a thin flexible pavement structure with a deep drainage system. It is instrumented with subsurface temperature, volumetric moisture content and groundwater probes. The mechanical response of the pavement structure was investigated using Falling Weight Deflectometer (FWD) measurements. The second part of the thesis (paper III and IV) are based on laboratory experiments and investigates different recent approaches that have been proposed to apply principles of unsaturated soil mechanics for incorporating seasonal variation of moisture content into the resilient modulus models using matric suction. The third part of the thesis (paper V) builds a bridge that spans between the laboratory and field investigations with an attempt to evaluate one of the predictive models presented in Paper III. The fourth part of the thesis (paper VI) mainly focuses on the laboratory-based investigation of the permanent deformation characteristic of subgrade soils. In this part, the permanent deformation characteristics of two different silty sand subgrade soils were investigated and modelled using the data obtained from repeated load traxial tests. Paper I mainly focuses on the spring-thaw weakening of the pavement structure. The environmental data collected using different sensors and the FWD tests were used to investigate variations in moisture content with thaw penetration and its influence on the stiffness of unbound layers and the pavement’s overall bearing capacity. Using the backcalculated layer stiffness and corresponding in situ moisture measurements in the unbound layers, a degree of saturation-based moisture-stiffness model was developed for the granular material and the subgrade. In Paper II, the drainage system of the structure was manually clogged during a three month period in summer to raise the groundwater level and increase the moisture content of the layers. Along with the subsurface groundwater level and moisture content monitoring, the structural response of the pavement was studied. In this research work, the FWD tests were conducted at three different load levels. The stress dependent behaviour of the unbound granular layer and the subgrade soil were further studied using the multilevel loads FWD test data. Additionally, parameters of a nonlinear stress-dependent stiffness model were backcalculated and their sensitivity to in situ moisture content was studied. In Paper III and IV, series of suction-controlled repeated load triaxial (RLT) tests were conducted on two silty sand (SM) subgrade materials. Several resilient modulus prediction models that account for seasonal moisture content variation through matric suction were summarized and after optimizing the model parameters, the capability of the prediction models in capturing the material response were evaluated. In Paper V, an attempt was made to evaluate the proficiency of one of the suction-resilient modulus models using the field moisture content and FWD measurements from the Torpsbruk test site. The backcalculated subgrade stiffness dataset at different moisture contents were compared with resilient modulus models obtained from the suction-resilient modulus predictive model. Paper VI presents an evaluation of several permanent deformation models for unbound pavement materials that incorporate the time-hardening concept using a series of multistage repeated load triaxial (RLT) tests conducted on silty sand subgrade materials. The permanent deformation tests were conducted at four different moisture contents with pore suctions measurement throughout the test. The effect of moisture content (matric suction) on the permanent deformation characteristics of the materials and the predictive model parameters were further investigated. / <p>QC 20150324</p>