Inhomogeneity of low-noise wearing courses evaluated by tire/road noise measurements using the close-proximity method

Performing numerous analyses of tire/road noise measurements on low-noise pavements during the last several years, the authors observed significant inhomogeneity of the wearing course in numerous cases, while similar problems were almost non-existent when dense pavements were measured.     

季冻区沥青混合料疲劳寿命的组成及变化特性研究

沥青混合料的疲劳裂缝是导致沥青路面面层破坏的主要原因之一,也是加速引起沥青路面水损害、老化等的重要原因。采用应力控制模式加载下的小梁弯曲试验,研究了不同温度或应力比下沥青混合料疲劳寿命的组成及变化特性。研究发现,沥青混合料的疲劳全寿命随温度的升高而缩短;相同温度时,沥青混合料的疲劳全寿命随着应力比的增大而缩短。当温度偏高时,沥青路面疲劳拓展寿命占据疲劳全寿命的比例较大;当温度偏低时则相反。疲劳全寿命的对数值与温度、应力比均成反比。裂纹拓展寿命占疲劳全寿命的百分比和温度呈指数关系。     

Pyrolysis of carbonaceous foundry sand additives: Seacoal and gilsonite

Seacoal and gilsonite are used by the foundry industry as carbonaceous additives in green molding sands. In this study, pyrolysis was used to simulate the heating conditions that the carbonaceous additives would experience during metal casting. Gas chromatography–mass spectrometry was used to tentatively identify major organic products generated during their pyrolysis at 500, 750, and 1000 °C. A number of compounds of environmental concern were identified during the pyrolysis of seacoal and gilsonite, including substituted benzenes, phenolics, and polycyclic aromatic hydrocarbons (PAHs). These thermal decomposition products, and especially PAHs, were generated at each pyrolysis temperature in all foundry sands containing seacoal. In gilsonite-amended sand, however, mainly alkanes and alkenes were identified at 500 and 750 °C and PAHs at 1000 °C. Compared to seacoal, the most intense peaks occurred during the pyrolysis of sand containing gilsonite. The greatest loss of pyrolyzable material also occurred during heating of gilsonite-amended sand from ambient temperature to 1000 °C in a thermogravimetric analyzer. The results obtained from this study will be useful to green sand foundries looking to reduce volatile hydrocarbon emissions.     

浅谈碾压混凝土路面的技术条件

文章从碾压混凝土路面的发展历程分析了发展碾压混凝土路面需要的技术条件，并从设备条件和施工技术两方面对我国的情况进行了论述，认为目前我国已具备发展碾压混凝土路面的技术条件。     

沥青路面的温度状况及弯沉和曲率半径测定中的温度修正系数

沥青路面的强度随温度的变化而不同,因此评价路面强度时,必须首先掌握沥青路面的强度与温度之间的关系。本文根据大量的系统观测数据,分析研究了沥青路面的温度状况及其规律性,对实用中的主要问题,即代表温度的确定及推算方法,强度的温度修正系数等,提出了新的可行方法。本文方法已为有关“规范”采用。     

用炭黑加劲的沥青混合料的性状

本文通过室内试验和代表性路面的结构分析表明,掺加15—20%的丸状炭黑(以结合料重量计),可以改善沥青混凝土的温度敏感性,有助于减轻低温开裂和减少高温时的车辙量,而其疲劳寿命并未受到不利影响。     

路面养护改建项目的优先次序评定

针对路面养护改建项目优先级的确定问题，提出了一种多属性决策的分析方法，在不需要主观赋权的情况下，该方法能对反映道路状态的多属性指标进行客观自动赋权。最后，使用该法对沥青路面养护改建项目进行了优先级排序分析。     

受移动集中力作用的沥青路面永久变形的精确解

推导出一种有别于其他数值解(如有限元法)的预估沥青路面永久变形的理论精确解。运用莫尔-库仑屈服条件和半空间内一点受集中力作用的Mindlin解,确定荷载作用下的沥青路面弹塑性分界面。利用刚塑性假定简化一维Burgers模型,从而简化了沥青路面的永久变形计算,据此假定将一维的沥青混合料Burgers模型推广至三维Burgers模型,类似于三维虎克定律。基于以上假定,计算出沥青路面下凹和隆起的永久变形,得出沥青路面侧向隆起高度约为下凹深度的一半,这一关系已被大量工程观测数据所证实。