In-site health monitoring of cement concrete pavements based on optical fiber sensing technology

Premature stress of cement concrete pavements i the coupled action of construction technique,structural ma-terial and environmental action.It is quite diffiault to accurately get the actual stress distribution merely based on the theoretical or simulation analysis.Ther efore,in-situ health monitoring is particularly si gnificant to obtain the stress or strain information for the assessment on structural perfor mance of cement concrete pavements.To contribute this topic,different kinds of FBG based sensors have been specially designed to measure the tem-perature,pressure and deformation in cement concrete pavements.A relatively long-term monitoring has been aonducted to collect the effective data after the solidification of the pavement lasts for about 15 d.Data analysis indicates that the temperature variation inside the pavement was very stable,with maximum ampltude smaller than 2.25°C in Sep.2020.The longitudinal,transverse and ver tical deformations of the pavement behaved in non-umniform distribution,and partial me asuring points suffered from large tensile force.The concrete course had better deformation resi stance than that of the soil base,and local interfacial micro void defects existed in the soil base.The preliminary results can help to understand the actual structural performance of cement concrete pavements based on the optical fiber sensing sys tem.

Modelling of the variation of granular base materials resilient modulus with material characteristics and humidity conditions

This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines content and the percentage of fractured coarse aggregates were identified as direct indicators of the resilient modulus susceptibility to changes in water content.The results showed that the percentage of fractured coarse aggregates particles(FR)has a more significant impact on the resilient modulus(Er)of crushed granular materials used in pavement construction than the combined indicator of the fines content and sample volumetrics(nf).Crushed granular materials with a higher percentage of fractured coarse aggregates are relatively insensitive to changes in the degree of saturation,but become more sensitive as the fine fraction porosity decreases.An adjusted model was proposed based on the existing formulation,but considers a complex parameter to describe and adjust the sensitivity of base granular materials to variations in moisture content with respect to fabrication charac-teristics,fines content and volumetric properties.The model shows that the variation of Er values is below10%for fully crushed granular materials.However,it reaches approximately±12%for materials with 75%of crushed coarse aggregates andþ40%and-25%for materials with FR=50%.This model could help select good ag-gregates characteristics and adjust grain-size distribution for environments where significant moisture content variations can occur in the pavement system,such as in the Province of Quebec(Canada).As it is based on pa-rameters that can be easily determined or estimated,it also represents a valuable tool for detailed design and analysis that can consider material characteristics.

Study on Test Methods for Mechanical Properties of Semi-rigid Base Cores of In-service Pavements

Compressive strength and compressive resilience modulus are two important parameters to measure the mechanical properties of semi-rigid base.The test methods of semi-rigid base cores are different from those of the laboratory samples in terms of sample acquisition,sample selection and humidity requirements.Core-drilling location,size of core sample,smoothness and humidity conditions were analyzed.The test methods of compressive strength and compressive resilience modulus were proposed.The research results show that compressive strength of lime fly-ash stabilized gravels base has a tendency of increasing during a long period.The compressive resilience modulus increases significantly with compressive strength of semi-rigid base.The compressive resilience modulus generally is 3-4 times than the recommended range of asphalt pavement design specifications.The fluctuation range of compressive resilience modulus is obviously higher than the compressive strength.The compressive resilience modulus is more sensitive to the construction variability.The overall trend between the compressive resilience modulus and the back-calculation modulus is consistent.FWD(falling weight deflectometer)back-calculation modulus can reflect the stiffness and bearing capacity of asphalt pavement.

Numerical analysis of reflective cracking and fatigue lives of semi-rigid pavement structures using ABAQUS and FE-SAFE

In order to compare the impact of thickness of different layers on fatigue lives of different semi-rigid asphalt pavement structures, the mechanical results from finite element models in ABAQUS are incorporated with the fatigue results from fatigue models in FE-SAFE to calculate the mechanical response and fatigue lives of semi-rigid pavement structures under heavy traffic loads. Then the influences on fatigue lives caused by the changes in the thickness of layers in pavement structures are also evaluated. The numerical simulation results show that the aggregated base and the large stone porous mixture （LSPM） base have better anti-cracking performance than the conventional semi-rigid base. The appropriate thickness range for the aggregated layer in the aggregated base is 15 to 18 cm. The thickness of the LSPM layer in the LSPM base is recommended to be less than 15 cm.

Compressive strength and frost heave resistance of different types of semi-rigid base materials after freeze-thaw cycles

Freeze-thaw damage is the most common disease of semi-rigid bases in cold regions, which may greatly affect the dura- bility of roadways. In this study, the compressive strength and frost resistance of four different types of semi-rigid bases （lime-fly ash-stabilized sand, cement-stabilized sand, lime-fly ash-stabilized gravel, and cement-stabilized gravel） are assessed by varying the materials content. Based on freeze-thaw and compressive strength tests, this paper presents the performance of the different materials, each having different physical properties, and the optimal amounts of materials contents are proposed.

Research on China's high-grade highway design index of asphalt pavement with granular base

Based on the 2006 Chinese asphalt pavement deflection value design index, we used KENLAYER Pavement Analysis and Design software and lstOpt statistical analysis software to can-y on the nonlinear regression, this paper establish high-grade highway design equations for the compressive slrain of soil sub-base top （CSSBT） and the radial compressive stress of semi-rigid base top （RCSRBT）. The correlation coefficients inspection standard to get precise proof, which means that our granular base design equations have high credibility and can be used in the Chinese design index of asphalt pavement with granular base （APGB）.

移动荷载下道路病害的弯沉盆特性

移动荷载作用下道路弯沉盆蕴含路基、路面的病害信息,充分利用移动弯沉盆信息开展道路病害快速无损检测受到行业重要关注。该文通过分析道路病害的弯沉盆特性,为移动弯沉车开发道路病害检测方法提供技术参考。首先建立半刚性基层沥青路面有限元模型,通过设置不同类型和程度的病害有限元模型,分析在移动荷载作用下路表弯沉盆的连续变化情况。结果表明:荷载移动到病害区域时,各病害模型中路表弯沉盆的中心弯沉值均会变大;路面结构层出现横向裂缝时,弯沉盆的形状会发生明显变化,贯通性横向裂缝对弯沉盆形状的影响最明显;基层与底基层局部松散对弯沉盆形状的影响比面层松散对弯沉盆的影响更明显;土基顶部出现空洞时,弯沉盆形状变化不明显;路基唧泥病害会严重影响路表弯沉盆形状与大小。

木质素纤维增强型透水性沥青稳定碎石疲劳研究

为提高增强型透水性沥青稳定碎石(asphalt treated permeable base,ATPB)的抗裂性能和耐久性,以SBS改性沥青为胶结材料配制掺入木质素纤维的ATPB混合料——纤维增强型透水性沥青稳定碎石(fiber asphalt treated permeable base,FATPB),并制作不同木质素纤维掺量的FATPB-25梁式试件进行不同应力比下的四点弯曲疲劳试验。将木质素纤维掺量为0.3%的FATPB-25与普通的AC-25、ATB-25的疲劳性能进行对比分析,探究考虑失效概率的应力比与纤维掺量对疲劳寿命的影响。研究结果表明:纤维掺量为0.3%的FATPB-25的抗疲劳性能明显比普通的AC-25和ATB-25的高,可用作耐久型的透水性下面层或柔性基层;通过包含失效概率的双对数方程可以对FATPB-25的疲劳寿命进行预测。

半刚性基层开裂的沥青路面承载力响应特性

为研究半刚性基层开裂对沥青路面承载力响应特性的影响,采用ABAQUS软件建立具有不同形态基层反射裂缝的沥青路面三维模型,研究其在载荷作用下的路面承载力响应特性,揭示响应机理。研究结果表明:反射裂缝越长,路面承载力响应越大。反射裂缝在贯穿路表前后,承载力响应由弱至强发生激增,反射裂缝只在一定宽度范围内影响承载力响应。给出了处治基层反射裂缝的指导建议,即结合现行方案,注意区分反射裂缝和面层裂缝,限制反射裂缝的发展。从长度、宽度、结构层位3个角度分析了反射裂缝对承载力响应特性的影响,仿真结果与现场实测结果相吻合,为研究半刚性基层沥青路面的承载力响应特性提供参考。

基于截尾分布的永久路面结构可靠度分析

为建立基于实测参数变异范围的永久路面结构可靠度分析方法,首先基于概率等效原则和逆变换法建立参数“有界”性的双侧截尾分布随机数抽样方法;然后选取现行沥青路面设计规范中面层、基层和路基结构的验算指标建立极限状态方程并开发多指标可靠度计算程序,将分析结果与理论分布随机变量可靠度程序对比;最后结合实测参数变异性水平,使用建立的可靠度分析方法评估京德高速永久路面结构的工后可靠度。结果表明:截尾分布更符合工程参数的真实分布,计算的可靠度更准确;中等交通荷载等级下,京德高速的路面结构可靠度为95.2%~98.7%;在累计当量轴次失效点后,永久路面结构面层、基层和路基的可靠度值均随轴次的增大而减小,且荷载越大,可靠度值下降速率越快,可靠度也越低。

半刚性基层沥青路面病害及其防治研究

为了提高半刚性基层沥青路面的建设水平,文章依托某国道一级公路,分析了路面反射裂缝、车辙等病害的产生原因,通过ABAQUS软件建立计算模型,分析了反射裂缝的受力和车辙的变形规律,同时提出了采取加铺玻纤格栅、确定基层预切缝间距等措施来处治路面病害,研究成果可为类似项目提供借鉴。

大厚度柔性基层长寿命沥青路面试验研究

为研究大厚度柔性基层沥青路面结构内部力学行为特征及疲劳寿命,以田新高速试验段、主路面结构为原型,分别制作全厚路面结构模型,开展同条件下沥青稳定碎石柔性基层和水泥稳定碎石半刚性基层沥青路面结构静力加载对比试验。采集不同轴载、温度工况下各层位力学响应值,进行变化规律拟合分析,并根据实际工况计算分析疲劳寿命。结果表明,同条件下,沥青稳定碎石柔性基层沥青路面结构下面层底、基层底的横向及纵向应变和竖向压应力指标均明显小于水泥稳定碎石半刚性基层沥青路面结构,且2种结构的下面层底各力学指标均大于其对应基层底指标;2种结构下面层、基层的疲劳寿命对数值随荷载等级增加呈线性下降,前者受温度变化影响更小,且数值均较后者明显提高;正常环境温度和标准交通荷载下,沥青稳定碎石柔性基层大厚度沥青路面结构下面层与基层预期可实现长寿命。研究结果为长寿命沥青路面结构提供新的试验途径与评定方法。

基于双模量理论的柔性基层沥青路面结构响应分析

绝大部分路面材料力学参数具有显著的拉压差异性,而现行柔性基层沥青路面设计中仍采用较大的压模量作为设计参数,导致结构力学计算与分析误差较大,路面设计结果不可靠。为此,开展了基于双模量理论和传统线弹性理论的柔性基层沥青路面结构力学响应对比分析,揭示了结构参数对柔性基层沥青路面结构关键力学响应的影响规律。结果表明:基于双模量理论的力学响应计算结果与传统线弹性理论之间的偏差高达15%;结构层厚度对结构力学响应的影响较大,其中基层厚度的影响更显著;各结构力学响应均随上中面层厚度增大而减小,随下面层厚度增大而增大,均呈二次函数关系,最大变化幅度约为20%;路表弯沉、基层底纵向拉应力与拉应变均随基层厚度的增加而减小,路表横向拉应变随基层厚度的增加而增大,其中路表横向拉应变受其影响最为显著,变化幅度超过40%。研究成果可为基于双模量理论的柔性基层沥青路面结构设计提供参考。

泡沫沥青复合式冷再生混合料组成设计与性能评价

文中通过发泡试验确定了泡沫沥青的最佳发泡条件,采用马歇尔试验确定了RAP和RAI不同掺配比例下泡沫沥青的最佳掺量,测试分析了泡沫沥青复合式冷再生混合料的抗压强度、抗拉强度、水稳定性和动态模量等性能.结果表明:在发泡温度为160℃,发泡用水量为2.9%的条件下,沥青发泡效果最优;在最佳发泡条件下,RAP掺量为0%、20%、40%的三种方案对应的泡沫沥青最佳掺量分别为3.4%、3.1%、2.9%,此时,三种方案均有较好的抗压、抗拉、水稳定性,并且随着泡沫沥青冷再生混合料中RAP掺量的增加,柔化程度与抗拉性能均逐渐增大,但抗压性能与水稳定性能均有所降低.

钢渣细集料对水泥稳定砂岩基层路用性能影响研究

钢渣应用于路面基层时既能提高钢渣的综合利用,又有助于减少天然砂石材料的消耗。为了分析钢渣细集料对水泥稳定砂岩基层(CSSB)路用性能的影响,本文比较分析了不同钢渣细集料置换石灰岩细集料条件下CSSB的抗压强度、劈裂强度、收缩性能和水稳定性,并运用SEM结合能谱揭示了钢渣细集料对CSSB微观结构的影响。结果表明:钢渣细集料能够有效提高CSSB的后期强度,其中100%(质量分数)钢渣细集料置换率下CSSB的60 d强度相较于未掺钢渣试样提高了18.7%,但对CSSB的早期强度存在一定的负面影响;钢渣细集料能够改善CSSB的收缩性能,且掺量越高,改善性能越明显;尽管钢渣细集料能够提高CSSB的长期水稳定性,但会降低其短期的水稳定性。与未掺钢渣试样相比,28 d龄期时,100%钢渣细集料置换率下CSSB界面过渡区的m(Ca)/m(Si)质量比降低了62.95%,C-S-H凝胶明显增多,结构更密实。研究表明,通过控制合理的掺量,钢渣细集料可以作为传统砂石细集料的替代品,在路面基层中具有良好的应用前景。

土工格室加固砂基未铺路面APT试验研究

加速路面试验是在相关环境条件下通过施加受控车轮载荷来评价路面性能的一种有效方法。将四个未铺路面路段分为加固和未加固两部分进行加速路面试验。第1和第4部分是砂基,是在破坏后用骨料基替换的未加固部分。第2和第3部分是在骨料覆盖层下用新型聚合物合金(NPA)土工格室加固的砂层。在经过一定次数车轮碾压后,测量每个路段的车辙深度。用应变片监测NPA土工格室不同位置的水平应变。试验结果表明,NPA土工格室在改善未铺路面的稳定性和减少永久变形方面具有显著效果。在特定的试验条件下,土工格室加筋砂层的性能相当于相同厚度的A-1-a骨料,显示出保持土工格室结构完好无损对确保NPA土工格室加固基底的足够性能具有重要意义。最后的试验应变片测量显示,车轮路径下的NPA土工格室承受拉伸应力,而车轮路径外的土工格室承受压缩应力。

100%RAP乳化沥青冷再生混合料基层应用研究

为了评估使用乳化沥青再生剂和100%RAP的新型路面基层的效果,在连霍高速改扩建工程河南段修建了一个试验路段,采用FWD对其结构性能进行了12个月的弯沉监测和施工完成后第540天的车辙测试;通过室内验证试验,研究了成型方式对再生沥青混合料体积参数的影响,此外,测试回弹模量和间接抗拉强度,分析了松散混合料存储时间(7、14、28 d)、养护时间(1、3、7、26、56 d)对力学性能的影响。结果表明:室内力学试验验证了再生混合料刚度随养护时间的延长而增加;存储时间越长,短期内的刚度和拉伸强度值越高,当养护较长时间后,试验行为未得到验证;采用乳化沥青冷再生混合料作为基层是一种RAP替代方案。

半刚性路面基层养生期实验研究

文章介绍了一种实验方法,用于评估半刚性路面基层养生期的效果。该方法采用实验室模拟养生环境,通过观测和分析基层材料在不同养生时间下的力学性能、收缩性能和耐久性等指标,量化养生期对基层性能的影响。实验结果表明,适当的养生期对提高半刚性路面基层的各项性能具有显著作用。文章研究内容为优化基层材料设计和施工工艺提供了理论依据。

超载状态下半刚性基层沥青路面力学响应分析

基于弹性层状体系理论,应用BISAR软件对标准轴载和不同超载状态下半刚性基层沥青路面的力学响应进行分析,主要指标包括路表弯沉、行车方向水平拉应力和沥青面层竖向压应力。研究结果表明,超载状态下路面结构的力学响应值大幅度增长,将导致路面使用性能降低,缩短使用寿命。应加大超载运输治理力度,保障路面正常运营。

中国与澳大利亚沥青路面基层设计对比分析

在澳大利亚工程项目实施过程中,中企项目团队因惯性思维的影响,会经常以中国标准体系中的要求来衡量在当地市场建设中的各种行为,同时澳大利亚基层设计标准体系与中国标准有诸多差异,这些差异直接影响到项目实施的有效性和建设经验的可复制性,极大地增加施工及研究人员的工作难度。因此为指导中国企业在澳洲的工程项目实施,提升公司在南太平洋区域建设的业务能力和水平,对中澳公路沥青路面基层设计标准进行对比研究,共有3个方面的对比,分别为沥青路面基层材料对比、沥青路面基层结构组合设计对比、沥青路面基层结构设计方法对比。通过以上3个方面的中澳对比,对澳大利亚基层设计进行系统的研究,对指导中企在澳洲的工程建设有重要意义。