Alternate Method of Pavement Assessment Using Geophones and Accelerometers for Measuring the Pavement Response

Pavement instrumentation with embeddable in-situ sensors has been a feasible approach to determine pavement deteriorations. Determining pavement deflections during the passage of the load is a promising strategy to determine the overall performance of the pavement. There are different devices that apply loads to the pavements and measure the deflection basin, these include static, vibratory, or impulse loadings. Most commonly used are the static loading like Benkelman beam and impulse loading like the Falling Weight Deflectometer (FWD). However, these techniques are costly and the measurements are recorded infrequently, i.e., once per year or two years. This study focuses on the use of geophones and accelerometers to measure the surface deflections under traffic loading. To develop a method to measure pavement deflections, the sensors were submitted first to laboratory tests, and then tested in situ, in a full scale accelerated pavement test. In the laboratory, the sensors were submitted to different types of loading using a vibrating table. These tests were used to determine the noise and sensitivity of the sensors, and then to evaluate their response to signals simulating pavement deflections under heavy vehicles. The sensor response was compared with measurements of a reference displacement sensor. Different processing techniques were proposed to correct the measurements from geophones and accelerometers, in order to obtain reliable deflection values. Then, the sensors were evaluated in a full scale accelerated test, under real heavy axle loads. Tests were performed at different loads and speeds, and the deflection measurements were compared with a reference anchored deflection sensor. The main advantage of using accelerometers or geophones embedded in the pavement is to enable continuous pavement monitoring, under real traffic. The sensor measurements could also be used to determine the type of vehicles and their corresponding speeds. The study describes in detail the signal analysis needed to measure the pavement deflections accurately. The measurements of pavement deflection can be then used to analyze the pavement behavior in the field, and its evolution with time, and to back-calculate pavement layer properties.

Validation of Enhanced Integrated Climatic Model Predictions with New Jersey Seasonal Monitoring Data

Environment is one of the essential factors that influence pavement material behavior and consequently its performance. The variation of climatic patterns from region to region, coupled with the variation of site-specific conditions across North America, makes it difficult to develop standard models to account for seasonal variation in material properties that apply for all regions. Consequently, the need to develop regional models becomes an essential requirement for most transportation departments. The enhanced integrated climatic model (EICM) was evaluated to determine its suitability in predicting subsurface temperature and moisture conditions within New Jersey sites. The validation of the model used environmental data collected through pavement instrumentation of a large-scale research study under the sponsorship of the New Jersey Department of Transportation. Site-specific data were input to the model, and the model output parameters were compared against field-measured values. The results of the validation for two of the instrumented sites are reported. Results of the study do not indicate a high correlation between field-measured values and EICM-predicted temperature and moisture profiles for the various pavement layers.

Instrumentação da pista circular experimental do IPR/DNER

<p>Faz-se uma breve abordagem sobre as principais experiências brasileiras em instrumentação de pavimentos no campo. Apresenta-se ainda, a instrumentação da Pista Circular Experimental do IPR/DNER, realizada em 1998 através de convênio firmado entre o DNER e a ABCP, para estudar o recapeamento de pavimentos flexíveis com concreto - <em>whitetopping. </em>Esta instrumentação foi composta de seis extensômetros e duas células de carga embutidos nas camadas do pavimento e os registros das medições destes sensores foram comparados com valores calculados utilizando os programas computacionais: EL5YM5, DIPLOMAT, ILSL2 e KENSLABS, obtendo resultados aproximados nesta comparação, principalmente com os programas EL5YM5 e DIPLOMAT (com aderência).</p><p>ABSTRACT</p><p>This work consists of a brief summary about the main Brazilian experiences in field pavement instrumentation. It also presents the IPR/DNER Experimental Circular Track, accomplished in 1998 through agreement between DNER and ABCP, to study the overlay of flexible pavements with concrete - whitetopping. This instrumentation was composed of six strain gages and two load cells embedded within the pavement layers. Recorded measurements of these sensors were compared to calculated values using the following computer programs: ELSYM5, DIPLOMAT, ILSL2 and KENSLABS, obtaining approximate results in this comparison, mainly with the programs ELSYM5 and DIPLOMAT (with adherence).</p>

Indiana Subdrainage Experience and Application

The applications of pavement subdrainage in the state of Indiana are presented. A recent study evaluated pavement subdrainage systems and measured and predicted moisture conditions underneath various types of pavements. Camera systems were used for internal inspection of the edge and geocomposite drains. Pavement instrumentation included moisture blocks, pressure transducers, temperature probes, rain and outflow tipping buckets, and a data acquisition system. Ongoing research using a test site on I-469 at Fort Wayne, Indiana, is aimed at finding the optimum location and layer configuration in flexible pavement; it uses those instruments as well as a TDR system, neutron probes, resistivity probe trees, and an enhanced data acquisition process. The research is a long-term project that will build on the data base of material hydraulic characteristics and performance. Indiana Department of Transportation has formed a committee to address issues related to use of subdrainage. Some of the recommendations from the committee were to abandon geocomposite drains, use bigger concrete protector walls at outlet pipes, and implement a routine inspection and maintenance program for drainage systems.