Influence of asphalt thickness on performance of geosynthetic-reinforced asphalt: Full-scale field study

In this study, a series of controlled traffic loadings was conducted on unreinforced and geosynthetic-reinforced full-scale asphalt overlays. Unlike the common objective of using paving interlayers to mitigate the development of reflective cracks, the main purpose of adopting geosynthetics for this study was to render an increased roadway structural capacity. The project involved instrumented test sections constructed during the rehabilitation of an in-service roadway in Texas, USA. The rehabilitation involved repairing the pre-existing pavement, placing tack coat, installing a geosynthetic interlayer (except in the unreinforced section), and finally constructing a 75 mm-thick asphalt overlay. This overlay comprised a 50 mm-thick, dense-graded (TY-D) layer overlain by a 25 mm-thick, thin-overlay mixture (TOM) layer. Controlled traffic loadings were conducted, which involved driving standard and light axle loads directly above asphalt strain gauges that had been installed at mid-depth of the pre-existing asphalt layer. Comparison of tensile strains among the different test sections revealed significantly smaller tensile strains in the geosynthetic-reinforced sections compared to those obtained in the unreinforced section. Consequently, and even though geosynthetic interlayers have often been adopted to minimize reflective cracking in asphalt overlays, the field monitoring results generated in this study demonstrate that they also provide added roadway structural capacity.     

Effects of geosynthetics on reduction of reflection cracking in asphalt overlays

An experimental program was conducted to determine the effects of geosynthetic reinforcement on mitigating reflection cracking in asphalt overlays. The objectives of this study were to assess the effects of geosynthetic inclusion and its position on the accumulation of permanent deformation. Geogrid position, type of existing pavement, temperature, and joint/crack opening were varied in 24 model specimens tested. Crack propagation under repeated loading was monitored. Results indicate a significant reduction in the rate of crack propagation in reinforced samples compared to unreinforced samples and type of old pavement (concrete or asphalt pavement), geogrid position and temperature affected the type of crack propagation in asphalt overlays. Placing the geogrid at a one-third depth of overlay thickness from the bottom provided the maximum service life.     

Effect of geogrid-reinforcement in granular bases under repeated loading

The thickness of the base plays a crucial role in the stability of pavements and the lack of availability of good quality aggregates is a major concern in India and other countries. Loading on top of the base plays a crucial role in the design of pavements. Usually, the design of the pavement is done for standard axle load, however, in the field, in some of the cases, the vehicles are overloaded which results in a higher wheel load on the pavements. The current paper examines the performance of geogrid reinforced unpaved sections at higher stresses with the primary objective of reducing the thickness of base layer required in the field. Experimental studies were carried out using repeated plate load tests to obtain the optimum depth of placing the geogrid in granular base layer to achieve maximum reduction in rutting of pavement. Resilient deformation behavior of both reinforced and unreinforced sections are obtained and these values are utilized to predict the resilient modulus of the base sections. The paper also discusses the reduction in permanent deformation by the introduction of geogrid. Rut depth reduction studies were carried out in order to compare the performance of reinforced and unreinforced sections. The role played by the reinforcement in reducing the strains on top of the subgrade is studied in detail. A comparison is also carried out to understand the pressure distribution along the base layer and role played by the geogrids in reducing the pressure on the subgrade. Further, values of stress distribution angles were obtained for reinforced and unreinforced sections. It is evident from the studies that geogrids contributed to improved performance as well as reduction in thickness of the aggregate layer.     

Evaluation of geosynthetic reinforcement in unpaved road using moving wheel load test

The common cause of failure of the unpaved road is associated with undesirable ruts and deformations. Use of geosynthetic reinforcement is a solution to this pavement distress problem as experienced in limited research works, especially in the laboratory studies. This study presents the performance of geosynthetic-reinforced unpaved roads subjected to moving wheel load tests to investigate the effect of geosynthetic reinforcement on the pavement surface deformation of the unpaved roads. Unreinforced and geosynthetic-reinforced unpaved road test sections consisting of varied reinforcements were constructed in a test pit, 9 m long and 2.7 m wide. Geogrid and geotextile were used for reinforcing the unpaved road test sections. The rut depth was measured in the transverse direction of the wheel path after certain number of wheel passes. Traffic Benefit Ratio (TBR) and Performance Index (PI) were employed in the study for the evaluation of the effectiveness of geosynthetic reinforcement in unpaved roads. After 350 vehicle passes, the geotextile-reinforced and geogrid-reinforced test sections get rutting reduced by 44.89% and 28.57%, respectively. The test results indicate that inclusion of geosynthetic reinforcement significantly improves the rutting resistance and stability of reinforced test sections compared to the unreinforced test sections.     

半刚性基层沥青路面的破损原因和改进措施

该文通过对海宁市东西大道沥青路面病害情况的调查,分析造成半刚性基层沥青路面基层疲劳破坏的主要原因。据此提出了防止路面破损的改进措施;设计阶段调查交通量时,要充分考虑转移交通量和超载因素,并且有余地;面层应采用抗车辙、抗浸水的改性沥青和SMA混合料;半刚性基层上最好铺一层土工合成材料。     

超重载对改建沥青路面结构影响的有限元分析

以有限元软件ANSYS为计算工具,应用弹性和弹塑性理论,对重载沥青路面结构进行数值分析,研究了路面结构在双轮车辆荷载作用下的力学响应,提出了路面设计指标增加沥青层层底拉应变和路基顶面压应变控制指标。     

多层土工织物加筋的沥青路面力学性能分析

应用复合材料力学原理和有限元法对单层和多层土工织物加强沥青混凝土路面进行了力学分析,在行车荷载条件下,研究了不同土工织物层数加筋层数和弹性模量对加筋的沥青路面层底弯拉应力和路面弯沉的影响,以达到优化道路设计的目的。     

考虑拉压模量不同的沥青路面力学计算方法与分析

现行沥青路面设计理论为传统的线弹性理论,设计时采用抗压回弹模量作为材料刚度参数,并未充分考虑道路材料拉压模量具有显著差异的特点。为此,文章将双模量理论(即拉压模量不同弹性理论)引入到路面力学分析中,基于迭代思想建立考虑材料拉压模量不同的沥青路面结构数值计算方法,且利用ABAQUS二次开发平台UMAT编制计算子程序,对典型沥青路面结构进行力学分析。结果表明：路面关键点位的力学响应,基于双模量理论与传统线弹性理论的计算结果之间的偏差高达30%～50%,应引起高度重视;沥青路面表面存在着较大的拉应力和拉应变,应为沥青路面破坏源之一,建议将沥青面层的设计点位从层底移至路表轮隙区;应用双模量理论对路面结构进行力学分析可有效地解决道路材料弹性模量的不唯一性问题。     

浅谈水泥路面加铺沥青层

通过对水泥路面加铺沥青层进行调查分析研究,探讨了水泥路面加铺沥青层技术中的几个关键性问题,结果表明：水泥路面加铺沥青层技术是处理旧水泥路面行之有效的方法之一,在旧水泥路面改建中发挥着重要作用。     

Improvement of the engineering properties of asphalt pavements using a ‘soft’ compaction technique (AMIR-Compaction)

In most countries of the world asphalt pavement of road networks represents the biggest single investment in the transportation system. In Canada, asphalt pavement built over the past decade is worth more than 70 billion dollars (in 1984 dollars). In order to maintain the current road network at the present level of service and prevent it from further deterioration, over 6 billion dollars is needed anually.

Traditionally, asphalt overlays are widely used to rehabilitate existing deteriorated pavements. Unfortunately the new overlays have been observed to fail in a relatively short time. Thus the investment in overlays is lost.

Recent research based on the concept of relative rigidity has indicated that the rapid deterioration of new asphalt overlays is directly related to current construction equipment. It has been shown analytically and experimentally that steel rollers used in compacting the asphalt layer will result in surface cracks during construction. Traffic and environmental influences will accelerate the failure of the new layer.

This paper presents the results of a testing programme evaluating the engineering properties of asphalt slabs compacted by a new method using a compactor termed AMIR. The results showed that the AMIR compactor will prevent the formation of constitution cracks resulting in an increase of indirect tensile strength of 10% and an increase of direct tensile strength of up to 60% when compared to steel roller compacted asphalt slabs.     

旧路加宽改造施工中的若干技术问题

在原有道路基础上拓宽并在原混凝土路面上加铺沥青混凝土面层,可提高城市道路的交通运输能力和水泥路面的使用功能。但如何防止原有水泥路面以及拓宽路面与原有路面之间接缝的反射型裂缝的发生,是城市道路改造中遇到的一个新课题。     

大面积广场沥青路面的施工

上海通用汽车研发中心(广德)项目道路工程动态广场沥青路面的设计对平整度要求高。根据大面积广场沥青路面施工难点,结合工程实际,从原材料要求、配合比设计、机械设备的保障、施工过程等方面进行控制,确保工程质量达到国际平整度指数(IRI)的设计要求。广场3层沥青路面摊铺采用"井"字形错缝施工。采用大吨位双钢轮压路机静压,取得了满意的效果。     

导电沥青混凝土的电热和力学性能研究

以碳纤维作为导电材料,以沥青混合料为基体,可以制备出导电性能优良,用于路面融冰化雪的沥青路面材料.研究其导电机理、电热性能以及在车辆荷载作用下内部应力分布.数值算例表明,导电沥青混凝土具有优良的力学性能,能满足道路行车需求,且在一定的输入电压下产热,可以融化路面冰雪,有效地抵制冰雪灾害对交通运输的不利影响.     

基于市政道路沥青路面裂缝产生因素及对策研究

随着沥青混凝土路面得到广泛的应用,受到气温、地质结构、行车条件等影响,裂缝成为市政道路沥青路面常见的问题之一。因此,本文对市政道路沥青路面裂缝形成的因素进行分析,对症下药,提出可行性的防治措施。     

浅析农村公路沥青路面推移的问题

简述了沥青路面的推移现象,结合近年来农村公路建设中出现的问题,从交通量大小、超载车辆情况、路线纵坡设计、基层材料等方面分析了沥青路面产生推移的原因,并提出了防治措施,以提高沥青路面施工质量,确保沥青混合料的均匀性及表面平整度。     

低噪音沥青路面类型和机理及应用探讨

从降低交通噪音的现实意义入手,介绍了交通噪音的主要来源,进而提出各种有效的低噪音沥青路面类型及其降噪机理,并就各种低噪音路面的应用作了比较探讨,从而提高道路的降噪功能.     

高黏沥青改性剂在贵州省干线公路养护工程中的应用

以自主研发的高黏沥青改性剂PEA为研究对象,以日本进口改性剂和某国产品牌改性剂作为平行对比,分别对高黏沥青和高黏沥青混合料的性能进行分析,并铺筑排水沥青路面试验段。结果表明,掺加高黏沥青改性剂PEA制备的混合料路用性能和施工性能优良,具有较好的耐老化性。路面经现场检测,各项技术性能符合《排水沥青路面设计与施工技术细则》(征求意见稿)要求。     

沥青路面车辙成因分析与防治措施探讨

石化北路位于华南高温湿热地区,交通量大,重车多,为保证路面行车质量,延长路面寿命,应重点加强其路面的抗车辙性能.本文根据沥青路面车辙的形成机理,分析了影响车辙的沥青、集料、沥青混合料、结构层厚度、外部环境等因素,探讨了车辙的防治措施,并特此成果成功应用于该路路面设计.     

Interlayer bonding characterization of interfaces reinforced with geocomposites in field applications

Geocomposites are extensively used in asphalt pavements as they provide significant long-term pavement benefits. Indeed, when correctly installed, geocomposites enhance road pavement performance thanks to their waterproofing properties, stress absorbing membrane interlayer (SAMI) action and improved mechanical strength of the pavement. Nevertheless, the presence of an interlayer causes de-bonding effects that negatively influence the overall pavement characteristics. This paper presents an experimental investigation aimed at comparing the interlayer bonding characteristics of four different geocomposites with an unreinforced reference configuration, laid on an Italian motorway section, in which the reinforcement depth and the lower layer surface condition (milled or new) were also varied. Interlayer shear strength (ISS) was measured, on both cores and laboratory produced specimens, through Leutner and Ancona Shear Testing Research and Analysis (ASTRA) equipment. The ISS results showed that geocomposites can be successfully applied directly on milled surfaces. Moreover, the application of a normal stress, as in the ASTRA device, tends to mitigate any difference related to the specimen heterogeneity. Finally, existing laws, which correlate the results obtained with different shear equipment on unreinforced interfaces, were generalized by considering the presence of geocomposites and the corresponding ISS specification limits were proposed for both ASTRA and Leutner test.     

丙烯酸酯树脂在排水性沥青路面铺装中的应用研究

以高性能聚氨酯丙烯酸酯作为防水粘结材料进行排水性沥青路面铺装,有效改善了传统沥青混凝土路面抗滑性差、排水功能欠佳带来的安全性问题及因积水、渗水导致防水粘结层失效造成的道路病害,解决了排水性路面的关键技术问题。通过对排水性沥青路面综合技术研究实现路面铺装高温160℃5 h无流淌,路表温度50℃不粘轮等技术要求,并实现防水粘结材料与沥青混凝土粘结强度为4.07MPa,与水泥混凝土粘结强度为4.51MPa,低温柔韧性可达-20℃,2.0MPa压力下24h不渗水,耐磨性优良,以上优异性能保证了其作为防水层材料的高效性。