The mechanical characteristics of road pavement layers are influenced by moisture conditions. Drying and wetting change the moisture content of the materials used in pavement structures, consequently affecting the mec...The mechanical characteristics of road pavement layers are influenced by moisture conditions. Drying and wetting change the moisture content of the materials used in pavement structures, consequently affecting the mechanical response. An experimental program was conducted to evaluate elastic deformations of a road pavement structure utilizing repetitive rigid plate load tests in a model test-pit facility. A typical Brazilian pavement （a multilayer system composed of a concrete asphalt and coarse base, and subbase） was simulated in this test-pit with devices for measuring humidity （TDR （time domain reflectometry）） and suction （tensiometers） installed every 20.0 cm along the profile. A pair of displacement transducers was attached on the surface of the pavement structure to record deformations due to dynamic loads. Two levels of groundwater table were analyzed, verifying that the pavement structure displacement increases with groundwater table growth. The structural response was evaluated and compared in physical and numerical models, and the results confirmed that the higher groundwater levels caused the greatest pavement displacements.展开更多
The pavement strength is very important for the evaluation of backlog maintenance. The current trend in many developing countries used pavement conditions index-PCI in estimating maintenance costs. The PCI can only ju...The pavement strength is very important for the evaluation of backlog maintenance. The current trend in many developing countries used pavement conditions index-PCI in estimating maintenance costs. The PCI can only justify periodic and routine recurrent maintenance. The condition strength is rarely determined in a flexible pavement creating an opportunity for back long maintenance. This paper reports the study conducted to develop and improve the algorithm for estimating the adjusted structure number to estimate the remaining thickness of the flexible pavement. The analysis of eight ways of computing structure numbers from FWD data ware analyzed and found that the improvement of the HDM 3 - 4 models can influence the usefulness of data collected from road asset management in Tanzania. The algorithm for estimating structural numbers from CBR was improved to compute adjusted structural numbers finally used to estimate the remaining life of the flexible pavement. The analysis of the network of about 6900 km including ST and AM was found that 64.72% were very good, 12% were Good, 10% were fair and 7.84% were poor and 5.4% were very poor.展开更多
In order to reduce the disease risk stemming from asphalt concrete pavement and ensure the safety of road operation,we should pay attention to the structural design of long-life asphalt pavement,strengthen the selecti...In order to reduce the disease risk stemming from asphalt concrete pavement and ensure the safety of road operation,we should pay attention to the structural design of long-life asphalt pavement,strengthen the selection of long-term pavement materials,scientifically set the pavement mechanical performance indexes based on the calculation results of pavement structure thickness combination and modulus combination,and ensure the stability and durability of road pavement structure through the real-time establishment of three-dimensional finite element calculation model,as well as the integrated design that takes into consideration the aspects of road subgrade,semi-rigid base and asphalt layer.展开更多
The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Offici...The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Officials） design method. The main objective of this study was to compare flexible pavement design using 1993 AASHTO design guide and MEPDG. Five newly built Superior PERforming Asphalt PAVEments （Superpave）, designed using the 1993 AASHTO Design Guide, were selected as test sections for the design simulation study. Deflection data were collected approximately 8 to 10 weeks after construction using FWD （falling weight deflectometer）. The FWD deflection data were used to back-calculate the pavement layer moduli using three different back-calculation programs. The existing pavement structures were analyzed for a 10-year analysis period. The maximum numbers of years the existing pavement structures will be in a serviceable condition as well as the minimum thicknesses of different layers to serve for 10-years were also determined. Effects of changing subgrade modulus, target distress, and reliability were also investigated. The MEPDG design analysis shows that the 1993 AASHTO Guide-designed flexible pavements do not show the distresses currently observed in Kansas for the 10-year design period. The MEPDG design simulation shows that the thinner the pavement sections, the higher the permanent deformation. The existing pavement structures can serve for more than 20 years as per the MEPDG design analysis if the default failure criteria and nationally-calibrated models are used.展开更多
文摘The mechanical characteristics of road pavement layers are influenced by moisture conditions. Drying and wetting change the moisture content of the materials used in pavement structures, consequently affecting the mechanical response. An experimental program was conducted to evaluate elastic deformations of a road pavement structure utilizing repetitive rigid plate load tests in a model test-pit facility. A typical Brazilian pavement （a multilayer system composed of a concrete asphalt and coarse base, and subbase） was simulated in this test-pit with devices for measuring humidity （TDR （time domain reflectometry）） and suction （tensiometers） installed every 20.0 cm along the profile. A pair of displacement transducers was attached on the surface of the pavement structure to record deformations due to dynamic loads. Two levels of groundwater table were analyzed, verifying that the pavement structure displacement increases with groundwater table growth. The structural response was evaluated and compared in physical and numerical models, and the results confirmed that the higher groundwater levels caused the greatest pavement displacements.
文摘The pavement strength is very important for the evaluation of backlog maintenance. The current trend in many developing countries used pavement conditions index-PCI in estimating maintenance costs. The PCI can only justify periodic and routine recurrent maintenance. The condition strength is rarely determined in a flexible pavement creating an opportunity for back long maintenance. This paper reports the study conducted to develop and improve the algorithm for estimating the adjusted structure number to estimate the remaining thickness of the flexible pavement. The analysis of eight ways of computing structure numbers from FWD data ware analyzed and found that the improvement of the HDM 3 - 4 models can influence the usefulness of data collected from road asset management in Tanzania. The algorithm for estimating structural numbers from CBR was improved to compute adjusted structural numbers finally used to estimate the remaining life of the flexible pavement. The analysis of the network of about 6900 km including ST and AM was found that 64.72% were very good, 12% were Good, 10% were fair and 7.84% were poor and 5.4% were very poor.
文摘In order to reduce the disease risk stemming from asphalt concrete pavement and ensure the safety of road operation,we should pay attention to the structural design of long-life asphalt pavement,strengthen the selection of long-term pavement materials,scientifically set the pavement mechanical performance indexes based on the calculation results of pavement structure thickness combination and modulus combination,and ensure the stability and durability of road pavement structure through the real-time establishment of three-dimensional finite element calculation model,as well as the integrated design that takes into consideration the aspects of road subgrade,semi-rigid base and asphalt layer.
文摘The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Officials） design method. The main objective of this study was to compare flexible pavement design using 1993 AASHTO design guide and MEPDG. Five newly built Superior PERforming Asphalt PAVEments （Superpave）, designed using the 1993 AASHTO Design Guide, were selected as test sections for the design simulation study. Deflection data were collected approximately 8 to 10 weeks after construction using FWD （falling weight deflectometer）. The FWD deflection data were used to back-calculate the pavement layer moduli using three different back-calculation programs. The existing pavement structures were analyzed for a 10-year analysis period. The maximum numbers of years the existing pavement structures will be in a serviceable condition as well as the minimum thicknesses of different layers to serve for 10-years were also determined. Effects of changing subgrade modulus, target distress, and reliability were also investigated. The MEPDG design analysis shows that the 1993 AASHTO Guide-designed flexible pavements do not show the distresses currently observed in Kansas for the 10-year design period. The MEPDG design simulation shows that the thinner the pavement sections, the higher the permanent deformation. The existing pavement structures can serve for more than 20 years as per the MEPDG design analysis if the default failure criteria and nationally-calibrated models are used.
