解决高速公路沥青路面早期损坏的技术途径

在对国内大量高速公路调查研究的基础上,论述了我国高速公路沥青路面早期损坏的两种类型:属于短时期内发生的水损坏、车辙、开裂损坏,以及沥青路面的耐久性差、使用寿命短的深层次早期损坏。针对水损坏、车辙、裂缝等局部性质的早期损坏,从路面结构、材料、施工、设计、管理等各方面分析了原因,提出了一系列有效防治高速公路早期损坏的技术措施。     

Failure of greenstone, jasper and cataclasite aggregate in bituminous concrete due to studded tyres: Similarities and differences

In wintertime, the use of studded tyres is common in the Nordic countries, steeply in creasing road wear. Apart from reducing surface quality and durability, the airborne dust presents a potential health hazard. To reduce road wear and dust release, there is a tendency to use harder and more wear-resistant aggregate materials.On the roads in and around Trondheim, mid-Norway, three types of aggregate material are common: greenstone, jasper and ‘mylonite’, in fact a cataclasite. Extensive laboratory testing suggests that cataclasite aggregate has better wear resistance than greenstone, but less than jasper [Erichsen E, Schiellerup H, Gautneb, H, Ottesen RT, Broekmans M. Road dust in Trondheim — analysis of the mineral content of airborne dust. (In Norwegian.) Geological Survey of Norway, NGU-report 2004. 037; 2004. p. 73]. However , observations on fluorescence-impregnated plane and thin sections demonstrate that in practice, cataclasite wears faster than greenstone, which may be attributed to its oriented fabric, as opposed to the random fabric in greenstone and jasper. The original article by Rosiwal from 1896 [Rosiwal A. Neue Untersuchungser gebnisse über die Härte von Mineralien und Gesteine. Verhandlungen der kaiserlich-königlichen geologischen Reichsanstalt, vol. 17/18; 1896. p. 475–491] on abrasion hardness and anisotropy provides an elegant explanation for the field observations.     

Nondestructive evaluation of pavements using spectral analysis of surface waves in the frequency wave-number domain

The potential of using Spectral analysis of surface waves (SASW) for nondestructive testing of pavement and soil sites has been demonstrated in several publications. The usual SASW field testing and data analysis procedures and the assumption of a single propagation mode yield accurate results when there are no sharp changes in the stiffness of the site with depth. When this is not the case, however, difficulties arise in the interpretation of experimental data due to the participation of more than one mode in the wave field. In an earlier study, the multiple filter/crosscorrelation technique was suggested for analyzing multi-mode SASW signals. This technique, however, may not yield accurate results when propagation modes are closely spaced. A more general method using spectral analysis in the frequency wave-number domain is presented in this paper. Formulas are presented for determining a reasonably small number of surface measurements, and the accuracy of this method in resolving experimental dispersion curves is demonstrated for a pavement site.     

透水性沥青面层材料设计新法及应用

本文提出了一种根据主骨料空隙率设计透水性面层沥青混合料级配的新方法，根据这一方法设计的透水性沥青面层具有良好的路面使用功能，应用前景广阔。     

Combustion characteristics of coals using a drop-tube furnace

Fourteen coals were selected for char refiring tests using a drop-tube furnace (DTF) in order to compare with previous tests on a 1 MW combustion facility. Each coal was sieved into two size fractions (53-75 and 106-125 μm) and characterised using proximate analysis and conventional petrographic tests as well as a test for % unreactives using image-analysis. The coal fractions were then pyrolysed at 1300 °C for 200 ms in 1 vol% oxygen in nitrogen. The reactivity, morphology and surface area of the chars were evaluated using thermal, optical and adsorption techniques. Each char fraction was then passed through the DTF at 1300 °C using a residence time of 600 ms and a furnace atmosphere of 5 vol% oxygen in nitrogen to evaluate burnout propensity. The characteristics of the coals, the chars and the residues after refiring were compared to determine whether any links exist between burnout, intermediate char products and coal composition. The link between % unreactives and burnout was confirmed for high volatile bituminous coals. Results obtained from two low volatile coals confirmed that their burnout was better than predicted from their properties. For the S. American (Guasare) coal poorer than expected burnout was obtained, as in previous work, but only for the larger size fraction.     

Enhancement of combustion efficiency with mixing ratio during fluidized bed combustion of anthracite and bituminous blended coal

In order to investigate the effect of mixing ratio of bituminous coal to blended coal on the enhancement of combustion efficiency, combustion experiments of blended coal with anthracite and bituminous are done in a laboratory scale fluidized bed combustor (10.8 cm ID and 170 cm height). The gross heating values of anthracite and bituminous coal used in this study are 2,810 cal/g and 6,572 cal/g, respectively. Experimental parameters are fuel feed rate, superficial gas velocity and mixing ratio of bituminous coal to blended coal. The combustion efficiency increases with the mixing ratio of bituminous coal due to the lower unburned carbon losses and higher burning velocity of bituminous coal. The rate of combustion in the combustor was increased with mixing ratio resulted from a higher burning velocity of bituminous coal. The measured combustion efficiency experimentally is about 3.5-12.4% higher than that of the calculated value based on the individual combustion of anthracite and bituminous coal under the same operating conditions. The optimum mixing ratio (MR) of bituminous coal determined is around 0.75 in this study. This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University.     

Local calibration of rigid pavement performance models using resampling methods

The performance prediction models in the Pavement-ME design software are nationally calibrated using in-service pavement material properties, pavement structure, climate and truck loadings, and performance data obtained from the Long-Term Pavement Performance programme. The nationally calibrated models may not perform well if the inputs and performance data used to calibrate those do not represent the local design and construction practices. Therefore, before implementing the new M-E design procedure, each state highway agency (SHA) should evaluate how well the nationally calibrated performance models predict the measured field performance. The local calibrations of the Pavement-ME performance models are recommended to improve the performance prediction capabilities to reflect the unique conditions and design practices. During the local calibration process, the traditional calibration techniques (split sampling) may not necessarily provide adequate results when limited number of pavement sections are available. Consequently, there is a need to employ statistical and resampling methodologies that are more efficient and robust for model calibrations given the data related challenges encountered by SHAs. The main objectives of the paper are to demonstrate the local calibration of rigid pavement performance models and compare the calibration results based on different resampling techniques. The bootstrap is a non-parametric and robust resampling technique for estimating standard errors and confidence intervals of a statistic. The main advantage of bootstrapping is that model parameters estimation is possible without making distribution assumptions. This paper presents the use of bootstrapping and jackknifing to locally calibrate the transverse cracking and IRI performance models for newly constructed and rehabilitated rigid pavements. The results of the calibration show that the standard error of estimate and bias are lower compared to the traditional sampling methods. In addition, the validation statistics are similar to that of the locally calibrated model, especially for the IRI model, which indicates robustness of the local model coefficients.     

沥青砼路面在公路施工中的质量控制措施

沥青砼路面在公路工程中应用广泛,它的施工质量直接影响沥青路面在公路工程中的使用效果。结合实际工程经验,从施工放样、混合料运输、混合料摊铺、碾压等方面介绍并分析了沥青砼路面施工质量的控制措施。通过对沥青砼路面施工过程中主要环节的探讨,提出了提高沥青砼路面质量的施工措施和方法,对路面施工具有一定的借鉴意义。     

NJTxtr—A Computer Program Based on LASER to Monitor Asphalt Segregation

Abstract: This paper describes the research funded by the New Jersey Department of Transportation to develop an automated technology to monitor segregation during construction of hot-mix asphalt concrete pavements. A Laser-based system was used to measure surface texture and to detect segregation. Two segregated test sections and a control test section were tested to evaluate the applicability of Laser texture method to detect and quantify segregation. Laser texture data were gathered from all three sections. Ratios of texture in segregated areas to that in nonsegregated areas were set as the basis for detection of different levels of segregation. By combining the level of segregation and extent of segregation, an AREA index was developed to determine the acceptability of a pavement section. Based on AREA index, pay adjustment factors were proposed to reduce the payment to account for loss of pavement life due to segregation. Further remedial actions were proposed to correct segregated pavement sections with acceptable AREA index. Based on the above concepts, Windows-based computer program NJTxtr was developed to detect and quantify segregation. This computer program uses the Laser-equipment-collected pavement texture data and determines whether the pavement section is acceptable or unacceptable based on the level of segregation within a pavement section, and provides bonus or penalties to the contractor. The paper describes a novel technology using laser and associated software for construction quality control of asphalt concrete pavements. The proposed methodology was applied to detect segregation in an interstate highway section in New Jersey, and this section was repaved based on visual observation and recommendation from this study.     

Long-term performance and binder chemical structure evolution of elastomeric bituminous geomembranes

This paper presents the results of uniaxial tensile tests, flow-rate measurements, and size-exclusion chromatography (SEC), which are used to evaluate the ageing of elastomeric bituminous geomembranes (BGMs) that were installed 6, 10, 15, 20, and 30 years ago in ponds at two different sites in France. SEC was used to detect oxidation and the absence of polymer in the bitumen at the surface of the 20- and 30-year-old BGMs. The results indicate that, for BGMs exposed less than 20 years, there was no oxidation or degradation of the polymer at the core. However, the elastomeric polymer was altered at the core of the 30-year-old BGM, resulting in an embrittlement of the bitumen, but this did not affect the mechanical properties of the glass veil and nonwoven polyester geotextile in the BGM core. Lastly, the flow rates through the BGM measured according to EN 14150 are still below 10^?6 m³ m^?2 d^?1, which indicates that the elastomeric bituminous GM is still watertight after 30 years of exposure.