Stiffness characterisation of full-scale airfield test pavements using computational intelligence techniques

The falling weight deflectometer (FWD) is a non-destructive test equipment used to assess the structural condition of highway and airfield pavement systems and to determine the moduli of pavement layers. The backcalculated moduli are not only good pavement layer condition indicators but are also necessary inputs for conducting mechanistic based pavement structural analysis. In this study, artificial neural networks (ANNs)-based backcalculation models were employed to rapidly and accurately predict flexible airport pavement layer moduli from realistic FWD deflection basins acquired at the U.S. Federal Aviation Administration's National Airport Pavement Test Facility (NAPTF). The uniformity characteristics of NAPTF flexible pavements were successfully mapped using the ANN predictions.     

Evaluation of layer properties of flexible pavement using a pseudo-static analysis procedure of Falling Weight Deflectometer

Most backcalculation programs used to evaluate the pavement layer properties assume static deflections even though dynamic deflections are generated from the Falling Weight Deflectometer (FWD). This study aims to take into consideration the dynamic effects of the deflection basin from the FWD in the backcalculation procedure. A Pseudo-static backcalculation procedure, named DYN-BAL (Dynamic BALMAT), was developed to calculate the layer moduli after converting dynamic deflections into static deflections. In situ tests were carried out to evaluate the applicability and reliability of the backcalculation procedure, which can accommodate the dynamic effect. In situ tests included FWD tests at the site of a Multi-Depth Deflectometer (MDD) installation. From the test results, it was found that DYN-BAL gives the most reliable results when compared with several other computer codes in use.     

水泥混凝土路面板模量反算的一种新方法--惰性弯沉法

路面结构层模量反算方法有多种,但都因反算解的唯一性问题而使反算结果误差太大.为了提高反算精度,本文提出了"惰性点"的概念.发现在混凝土路面的弯沉盆上,存在一个其弯沉值几乎不随面层模量变化而改变的点,该点即被定义为惰性点.该点的发现,为唯一确定路面结构层模量提供了理论基础.     

沥青路面结构参数对弯沉盆影响分析

利用多层弹性体程序BISAR,分析沥青路面结构层模量对弯沉盆影响。结果表明:面层模量的变化对中心点的弯沉影响最大;基层模量的变化对d0、d20、d30的影响最大;底基层模量主要的影响测点范围为0～120cm;d210与土基模量关系密切,而上层路面结构层模量和厚度对d210影响微小。同理,分析厚度对弯沉盆影响。结果表明:面层和基层厚度变化对d30影响最大。最后根据嘉浏高速公路FWD检测数据,验证了影响规律。     

基于FWD弯沉数据的模量反算方法及影响因素

从模量反算问题的提出入手，对模量反算的方法和模量反算的影响因素进行了探讨，通过一定的理论分析计算，进一步说明了基于FWD弯沉数据模量反算的科学性与可行性，可为后续研究提供理论基础。     

Bridging the gap between laboratory and field moduli of asphalt layer for pavement design and assessment: A comprehensive loading frequency-based approach

Asphalt pavement is a key component of highway infrastructures in China and worldwide. In asphalt pavement design and condition assessment, the modulus of the asphalt mixture layer is a crucial parameter. However, this parameter varies between the laboratory and field loading modes (i.e., loading frequency, compressive or tensile loading pattern), due to the viscoelastic property and composite structure of the asphalt mixture. The present study proposes a comprehensive frequency-based approach to correlate the asphalt layer moduli obtained under two field and three laboratory loading modes. The field modes are vehicular and falling weight deflectometer (FWD) loading modes, and the laboratory ones are uniaxial compressive (UC), indirect tensile (IDT), and four-point bending (4PB) loading modes. The loading frequency is used as an intermediary parameter for correlating the asphalt layer moduli under different loading modes. The observations made at two field large-scale experimental pavements facilitate the correlation analysis. It is found that the moduli obtained via laboratory 4PB tests are pretty close to those of vehicular loading schemes, in contrast to those derived in UC, IDT, and FWD modes, which need to be adjusted. The corresponding adjustment factors are experimentally assessed. The applications of those adjustment factors are expected to ensure that the moduli measured under different loading modes are appropriately used in asphalt mixture pavement design and assessment.     

浅谈用FWD弯沉盆参数研究沥青路面反应模型

介绍了国外利用FWD弯沉盆参数研究沥青路面反应模型的现状,分别对一些研究者提出的疲劳开裂模型和车辙模型进行了具体阐述,指出无论采用哪种FWD弯沉盆参数,都从不同侧面反映了路面反应与FWD弯沉盆参数的内在关系。     

基于FWD动态弯沉盆进行模量反算方法概述

指出利用弯沉盆数据,对路面各结构层材料模量(性能)进行反算,是评价路面工作性能的重要手段,参考了大量相关文献,就目前国内外常用的反算方法进行了分析比较,对模量反算方法进行了展望。     

An approach for optimizing pavement design–redesign parameters in PPP projects

Modeling the elasticity modulus of unbound granular pavement materials has attracted significant research interest because of its importance in pavement design particularly in PPP/BOT projects. These efforts have been hampered by three factors: (i) inability to capture the correlations between the asphalt and granular layers and the subgrade, (ii) inadequate modeling of the effects of external factors on the elasticity modulus of unbound materials, and (iii) widespread use of linear statistical relationships to model a complex and non-linear phenomenon. In this paper genetically optimized neural networks and falling weight deflectometer (FWD) back-analysis results from a newly constructed BOT project in Athens, Greece, are employed in order to evaluate pavement section design parameters. It is shown that parameter values adopted during design do not co-inside with those observed from the back-analysis studies. Further, the results indicate that the relative estimation error for the modulus of elasticity of the unbound material does not exceed 25%, while the correlation between actual and predicted values is 86%, both suggesting that the proposed approach models the physical phenomenon adequately, a finding with important practical implications particularly in PPP projects.     

Airfield pavement deterioration assessment using stress-dependent neural network models

In this study, an artificial neural network (ANN)-based approach was employed to backcalculate the asphalt concrete and non-linear stress-dependent subgrade moduli from non-destructive test (NDT) data acquired at the Federal Aviation Administration's National Airport Pavement Test Facility (NAPTF) during full-scale traffic testing. The ANN models were trained with results from an axisymmetric finite element pavement structural model. Using the ANN-predicted moduli based on the NDT test results, the relative severity effects of simulated Boeing 777 (B777) and Boeing 747 (B747) aircraft gear trafficking on the structural deterioration of NAPTF flexible pavement test sections were characterized. The results indicate the potential of using lower force amplitude NDT test data for routine airport pavement structural evaluation, as long as they generate sufficient deflections for reliable data acquisition. Therefore, NDT tests that employ force amplitudes at prototypical aircraft loading may not be necessary to evaluate airport pavements.     

落锤式弯沉仪(FWD)与贝克曼梁(BB)的相关性分析

以古神公路沥青混凝土路面为研究对象,分析了贝克曼梁与落锤式弯沉仪(FWD)在检测沥青混凝土路面弯沉时的相关性,并建立FWD与贝克曼梁检测数据的线性回归公式,对该地区道路状况评定具有借鉴意义。     

泡沫沥青冷再生技术

根据旧路调查和FWD弯沉测试结果,确定再生深度,形成了泡沫沥青稳定碎石基层和泡沫沥青混合料面层两种冷再生方案,确定了稳定剂最佳剂量的选择方法,初步形成冷再生混合料的配合比设计方法。从后期观测情况来看,路面使用状况良好。     

FWD检测技术在路面养护工程中的应用

锤式弯沉仪(简称FWD)作为无损检测设备已经被广泛地应用于路面结构层评价,但缺乏针对破损路面检测的成果和工具。以嘉浏高速公路养护工程为依托,开发了针对高速公路破损路面结构层评价的程序,并探索FWD在实际工程中的应用。     

基于FWD的沥青路面动态弯沉温度修正系数

基于不同沥青路面的结构厚度和温度参数,对FWD实测的动态弯沉计算结果进行修正研究。按照分阶段函数拟合方法,建立弯沉修正系数与路面结构厚度、温度的两参数关系模型;该模型充分考虑沥青混合料模量的温度敏感性,可以保证当结构层厚度为0℃或温度为20℃时, 弯沉修正系数为1,当温度升高或降低时,修正系数趋于一个稳定的最小值或最大值。此模型具有明确的物理意义,可更好地反映出路面材料实际力学状态,使弯沉参数的判断和评价更为科学、有效。     

沥青路面反算模量与沥青混合料动态模量的关系

为获取沥青路面结构层沥青材料模量参数,合理评价沥青路面结构性能,开展沥青路面反算模量与同温度下室内沥青混合料动态模量的关系研究。采用落锤式弯沉仪（FWD）对4个不同结构的沥青路面试验路进行测试,并通过路面结构埋设的温度传感器同步采集温度,对试验结果进行沥青层模量反算;采用沥青混合料性能试验机（AMPT）对试验路沥青材料进行动态模量试验,根据时温等效原理获取FWD测试的同温度下的沥青混合料模量值,结合沥青路面结构层厚度计算沥青混合料动态模量的当量模量;对沥青层同一温度下的FWD反算模量与动态模量的当量模量进行分析比较,建立回归模型。结果表明,不同路面结构的FWD反算模量与室内动态模量的关系基本一致,其变化趋势不依赖于沥青层厚度的变化;沥青路面FWD的反算模量和室内AMPT的模量呈非线性关系,当模量较小时,FWD反算模量要低于室内模量,随着模量的增加,在10000MPa附近时,二者的模量值是接近的,模量值再继续增大时,FWD反算模量的增加较快,明显大于室内动态模量,室内动态模量的增长趋于平缓。     

沥青混合料动态压-拉双模量及其在路面响应分析中的应用

沥青混合料层模量是沥青路面响应分析的必备参数,其数值的准确性关乎路面设计结果的可靠性。受骨料嵌挤作用的影响,沥青混合料在承受压应力与拉应力时模量表现不同。文章旨在从双模量的角度分析沥青混合料的动态压-拉模量特征,并将压-拉双模量用于路面响应预测,探讨双模量体系下的路面响应特点。首先,基于双模量框架下的有限元模型,建立间接拉伸试验中沥青混合料压 拉双模量、泊松比的计算方法;其次,以一种密级配混合料(AC-13)为例,分析沥青混合料在不同温度与加载频率下动态压-拉双模量、压-拉泊松比与单模量、单泊松之间的差异性;最后,将所确定的压 拉模量及泊松比用于路面沥青层力学响应预测,并与现有的单模量体系下的预测结果进行对比,分析单、双模量两类体系下路面力学响应的特点及其联系。研究表明,AC-13混合料压模量主曲线在全频域内均明显高于拉模量主曲线;单模量体系计算的模量主曲线更接近于压模量主曲线,且所计算的泊松比在中高温时失效;混合料压 拉模量比值分布在1.6～4.0,随温度升高而升高。与双模量体系下路面响应计算结果相比,现有单模量体系模型低估了柔性路面沥青层应变响应及柔性/半刚性路面沥青层的最大剪应力响应,而弯沉响应计算结果具有较好的一致性。研究成果可为考虑材料压、拉模量差异性的路面设计提供参考。     

Uncertainties in determining the responses of reinforced flexible pavements using in-situ tests

A 225m long full-scale testing lane was constructed at a local road in Australia to evaluate the performance of the flexible pavements over a weak soft subgrade. The pavements were reinforced with three types of geosynthetic products: High-density polyethylene (HDPE) geogrid, HDPE geocomposite and fibreglass geocomposite. The road was divided into 15 sections with different configurations such as the thickness of the base course, reinforcement types and locations, and base course materials. A series of in-situ tests were conducted on each section to compare the behaviour of the pavement structures, such as the moduli of the subgrade, base course and asphalt layer. The comparison shows that there is a large variation in the properties of the structures and great uncertainties in determining the properties even within the sections with the same configuration. When the base course is weaker, the FWD tests may be able to detect the effect of the reinforcements below the asphalt seal layer. Smaller plates are recommended when determining the modulus of thinner base course layers using FWD or LWD tests to minimize the influences from the subgrade.     

水泥路面破损检测

列出了水泥路面破损基本类型,介绍了落锤弯沉仪的使用方法,阐述了落锤弯沉仪用于测定水泥路面破损的基本原理以及测试示例,根据水泥路面破损测试结果制定了合理的养护维修措施,以提高路面使用品质,延长使用年限。     

Instantaneous pavement condition evaluation using non-destructive neuro-evolutionary approach

In this paper, a hybrid neural network (NN)-genetic algorithm (GA) based non-destructive pavement auscultation method for instantaneous airfield infrastructure condition assessment is discussed. NNs are employed for finite element aided forward prediction of pavement surface deflections resulting from non-destructive test impulse loading and the GAs are used for global optimisation of the pavement structural parameters by matching the NN predicted deflections with the measured pavement response. This hybrid approach takes advantage of the non-linear estimation capability provided by neural networks trained using finite element (FE) solutions in modelling the stress-dependent behaviour of unbound pavement geo-materials while improving the robustness to measurement uncertainty through the application of genetic algorithms. The performance of the developed hybrid pavement auscultation technique is evaluated through extensive field studies conducted at a state-of-the-art full-scale airfield pavement test facility. The results show that this approach is promising for real-time condition evaluation of airfield pavement infrastructure systems.     

FWD在现场冷再生工程中的应用

结合工程实例,介绍了在现场冷再生工程中,采用FWD测试弯沉并反算模量后,结合路面破损调查,对旧路面进行综合评价的方法,总结了FWD测试道路弯沉的优点,以推广FWD在道路工程中的应用。