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.

路面结构层对高速公路加宽路基沉降的影响研究

为了预防和控制高速公路加宽工程路基出现差异沉降,保障工程质量,利用有限元法,系统分析了路面面层模量与厚度、基层模量与厚度、土基模量等对高速公路加宽路基沉降变形的影响规律。结果表明:路面结构层参数对于高速公路加宽路基的受力与变形特性具有显著的影响,高速公路加宽路基的沉降量随着路面结构层厚度和刚度的增大而显著减小,提升路面结构层的厚度和刚度可以有效预防高速公路加宽工程出现差异沉降。

Laboratory and field performance of recycled aggregate base in a seasonally cold region

The objective of this project was to characterize the freeze-thaw properties of recycled concrete(RCA)and asphalt(RAP)as unbound base and to assess how they behaved in the field for nearly 8 years.This paper includes an examination of existing information,laboratory studies of freeze-thaw behavior,and evaluation of data from Mn ROAD field-test sections in a seasonally cold region,i.e.,in Minnesota,USA.Test sections were constructed using recycled materials in the granular base layers at the Mn ROAD test facility.One test section included 100%RAP,another 100%RCA,a third one a 50/50blend of RCA/natural aggregate,and a fourth one only natural aggregate(Class 5)as a control.The stiffness(i.e.,elastic modulus)was monitored during construction and throughout the pavement life by the Minnesota Department of Transportation,along with the variation of temperatures and moisture regimes in the pavement to determine their effects on pavement performance.The resilient modulus of each material was determined by bench-scale testing in accordance with NCHRP 1-28a,as well as by field-scale tests incorporating a falling-weight deflectometer.Specimens were subjected to as many as 20 cycles of freeze-thaw in the laboratory,and the change in their resilient modulus was measured.In the field-test sections constructed with the same materials as the base course,temperature,moisture,and field modulus(from fallingweight deflectometer tests)were monitored seasonally for nearly 8 years.From the temperatures in the base course layer,the number of freeze-thaw cycles experienced in the field was determined for each test section.Inferences were made relative to modulus change versus freeze-thaw cycles.Conclusions were drawn for long-term field performances of the recycled base(RAB)in comparison to natural aggregate.

Mechanical response of continuously reinforced concrete pavement on foam concrete interlayer for two-way curved arch bridge

In order to research the mechanical response of continuously reinforced concrete pavement on foam concrete interlayer for a two-way curved arch bridge, the elliptical vehicle load is translated into the rectangular load based on the equivalence method. Then, a three-dimensional finite element model of the whole bridge is established. The reliability of the model is verified. Additionally, the mechanical response of continuously reinforced concrete pavement under vehicle loading is analyzed. Finally, the most unfavorable loading conditions of tensile stress, shear stress and vertical displacement are determined. The results show that the most unfavorable loading condition of tensile stress, which is at the bottom of continuously reinforced concrete pavement on the two-way curved arch bridge, is changed compared with that on homogeneous foundation. The most unfavorable loading condition of shear stress at the top is also changed. However, the most unfavorable loading condition of vertical displacement remains unchanged. The tensile stress at the bottom of about 1/4 span of the longitudinal joint, the shear stress at the top of intersection of transverse and longitudinal joint, together with the vertical displacement at the central part of longitudinal joint, are taken as design indices during the structural design of continuously reinforced concrete pavement on the two-way curved arch bridge. The results are helpful for the design of continuously reinforced concrete pavement on unequal- thickness base for the two-way curved arch bridge.

Characterisation, Analysis and Design of Hydrated Cement Treated Crushed Rock Base as a Road Base Material in Western Australia

Hydrated Cement Treated Crushed Rock Base （HCTCRB） is widely used as a base course in Western Australian pavements. HCTCRB has been designed and used as a basis for empirical approaches and in empirical practices. These methods are not all-encompassing enough to adequately explain the behaviour of HCTCRB in the field. Recent developments in mechanistic approaches have proven more reliable in the design and analysis of pavement, making it possible to more effectively document the characteristics of HCTCRB. The aim of this study was to carry out laboratory testing to assess the mechanical characteristics of HCTCRB. Conventional triaxial tests and repeated load triaxial tests （RLT tests） were performed. Factors affecting the performance of HCTCRB, namely hydration periods and the amount of added water were also investigated. It was found that the shear strength parameters of HCTCRB were 177 kPa for cohesion （c） and 42~ for the internal friction angle （~）. The hydration period, and the water added in this investigation affected the performance of HCTCRB. However, the related trends associated with such factors could not be assessed. All HCTCRB samples showed stress-dependency behaviour. Based on the stress stages of this experiment, the resilient modulus values of HCTCRB ranged from 300 MPa to 1100 MPa. CIRCLY, a computer program based on the multi-layer elastic theory was used in the mechanistic approach to pavement design and analysis, to determine the performance of a typical pavement model using HCTCRB as a base course layer. The mechanistic pavement design parameters for HCTCRB as a base course material were then introduced. The analysis suggests that the suitable depth for HCTCRB as a base layer for WA roads is at least 185 mm for the design equivalent standard axle （ESA） of 10 million.

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。

微表处用水性树脂基改性乳化沥青流变性能

机场道面微表处技术养护品质依赖于其胶结材料性能,为明确水性树脂聚合物掺量对微表处用改性乳化沥青流变特性的影响,制备了微表处用WER/WPU改性乳化沥青与WER/WPU/EVA改性乳化沥青,借助动态剪切流变试验、线性振幅扫描试验和弯曲梁流变试验,探明了不同水性树脂聚合物掺量下改性乳化沥青高温抗变形能力、中温疲劳性能与低温蠕变特性,对比分析了WER/WPU改性乳化沥青与WER/WPU/EVA改性乳化沥青的流变性能,并与现有研究中改性乳化沥青的抗变形、抗开裂能力进行了对比评价。结果表明:掺加树脂聚合物后乳化沥青材料的高温抗变形能力、中温疲劳寿命以及低温柔韧性得到有效提升,提升幅度随水性树脂聚合物掺量增加而提高;WER/WPU/EVA-15改性乳化沥青高温抗变形性能略优于WER/WPU-15改性乳化沥青,但其疲劳特性与低温抗裂性较WER/WPU-15改性乳化沥青略低。文中所研制的树脂基改性乳化沥青具有显著的先进性。

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。

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。

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。

Composition design and performance evaluation of rubber-particle cement-stabilized gravel

To improve the mechanical properties and durability of the cement-stabilized base,rubber particles of three different sizes and with three different contents were optimally selected,the evolution laws of the mechanical strength and toughness of rubber-particle cement-stabilized gravel(RCSG)under different schemes were determined,and the optimal particle size and content of rubber particles were obtained.On this basis,the durability of the RCSG base was clarified.The results show that with an increase in the rubber particle size and content,the mechanical strength of RCSG gradually decreased,whereas the toughness and transverse deformation ability gradually increased.1%content and 2–4 mm sized RCSG can better balance the relationship between mechanical strength and toughness.The 7 d unconfined compressive strength was 17.7%higher than that of the 4–8 mm RCSG.The 28 d toughness index and ultimate splitting strain can be increased by 9.8%and 6.3 times,respectively,compared with ordinary cement-stabilized gravel(CSG).In terms of durability,compared with CSG,RCSG showed a 3.7%increase in the water stability property of cement-stabilized base with 1%content and 2–4 mm rubber particles,5.5%increase in the frozen coefficient,and 80.6%and 37.9%increase in the fatigue life at 0.70 and 0.85 stress ratio levels,respectively.

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。

动载下复合式基层沥青路面的裂缝扩展行为研究

基于断裂力学理论及有限元数值模拟方法,建立塞内加尔MBOUR-KAOLACK(MK)高速公路带裂缝的复合式基层沥青路面三维模型,分析了不同荷载与路面结构层参数对复合式基层沥青路面开裂初期应力强度因子的影响,并与等厚半刚性基层路面对比,分析了裂缝在向上扩展时应力强度因子的变化规律。结果表明:随着车速的降低或轴重的增大,应力强度因子极值逐渐增大,路面裂缝扩展的风险增大。随着路面结构层厚度和沥青层模量的增大,应力强度因子则均在减小。其中,增大半刚性底基层与增大面层厚度对应力强度因子的降幅相近,故增大半刚性底基层厚度更经济。不过,底基层模量的增大会导致应力强度因子增大,也应避免使用过高模量的底基层。随着裂缝向上扩展,复合式基层沥青路面和半刚性路面的KⅠ先增大后减小,KⅡ逐渐增大,开裂主导模式逐渐由张拉型转变为剪切型。在裂缝向上扩展的过程中,复合式基层沥青路面的KⅠ降幅比半刚性基层路面更大,且其应力强度因子也小于半刚性基层沥青路面。可见,复合式基层沥青路面的抗裂性更好。

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。

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。

基于高延性水泥基材料基层的抗裂性能研究

为研究基层开裂问题,采用正交试验、荧光显微镜观察等试验方法,以提高延性为目的,采用硅酸盐水泥、聚丙烯酸钠、纤维、粉煤灰等材料,研发一种适用于基层的抗裂性水泥。结果表明水泥掺量4%、聚丙烯酸钠采用水泥的5%、掺PVA纤维6%的高延性水泥分布均匀、收缩应变小、抗裂性能佳。根据优选的高延性水泥的配合比,采用四点弯曲试验、改进的干缩试验、三点疲劳试验以及无侧限抗压强度试验,确认15%含泥量的混合料无侧限抗压强度达到7.7 MPa、疲劳次数超8800次,有效解决了“脏”集料在基层混合料的应用问题。

公路路面基层施工中水泥稳定碎石技术的分析

随着国家交通基础设施建设的快速发展,对公路路面的施工质量要求日益提高。基层施工作为公路路面施工的重要组成部分,其施工质量直接关系到路面的整体性能和使用寿命。在众多基层施工技术中,水泥稳定碎石技术因其优异的性能和经济性得到了广泛应用。在实际应用中,应严格控制原材料质量,合理选择配合比,加强施工过程监控,确保工程质量达到设计要求。对公路路面基层施工中的水泥稳定碎石技术进行深入分析,以期为相关工程实践提供参考。

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。