移动荷载下黏弹性半空间体上双层板的动力响应

采用黏弹性半空间体上无限大双层板模型模拟路面结构,通过三重Fourier积分变换得到单位脉冲荷载作用下路面动力响应的Green函数。根据线性系统的叠加原理,利用广义Duhamel积分推导出移动荷载作用下路面动力响应的解析解。采用自适应Simpson法编制了计算奇异、振荡函数的广义积分计算程序,完成了路面动力响应从波数-频率域到时间-空间域的转换。结合算例,对移动荷载作用下路面的振动规律进行研究,讨论上、下层板厚度和板材料的弹性模量对路面动力响应的影响,明确了路面结构的振动特性,研究结果可为路面结构的设计、施工提供理论指导。     

车辆速度与载重对路面结构影响的现场试验研究

针对车辆荷载与速度在路面结构破坏中的重要性,通过现场试验,对新建高速公路在不同载重及不同速度的车辆通过条件下路面的动态响应（动应变、动应力）规律进行了研究。研究表明,应力-应变峰值随载重的增加而增大,而随速度的增加而减小;前轮应力应变峰值随载重增加而增大的幅度总体上要小于后轮;前轮水平横向应变峰值随载重增加而增大的幅度要小于纵向,而后轮的横向应变与纵向应变的增幅比较接近;速度变化引起的应力应变幅值变化不如载重变化引起的显著;随着深度的增加,车辆行驶产生的动应力对路面的影响迅速减弱。     

矩形移动荷载作用下路面-双层地基系统三维振动分析

考虑路面和地基之间的相互作用,建立了路面-双层地基的三维模型,将车辆荷载模拟成矩形移动荷载,利用Fourier变换方法对车辆荷载作用下路面-双层地基系统的三维振动问题进行了研究。假设地基为上部弹性土体和下部为饱和土体组成的双层混合结构,整个系统置于刚性基岩上。通过引入势函数,利用Lame分解理论和积分变换方法分别对弹性土层和饱和土层进行求解。在Fourier变换域内,联立路面和下卧双层地基系统的的运动方程,获得了车辆荷载作用下路面-双层地基系统三维振动的位移和孔压响应的积分形式解,并利用IFFT算法和自适应数值积分算法得到了数值计算结果。研究结果可为路基动力响应分析提供参考。     

交通荷载作用下低路堤软土地基硬壳层应力扩散作用研究

为了研究硬壳层对低路堤软土地基动力响应的影响,将软土地基上的道路系统模拟成路面-路基-硬壳层-软土地基4层结构。假设路面、路基、硬壳层都为单相弹性土体,而软土地基采用饱和多孔介质模拟,通过积分变换法对模型进行推导求解,分别建立了路面、路基、硬壳层和软土地基的动力刚度矩阵,并考虑路表车辆荷载条件、层间连续条件和饱和软基表面透水条件,最终集成了道路结构的整体动力刚度矩阵,获得了车辆荷载作用下低路堤软土地基的动力响应解答。在该基础上,利用快速傅里叶逆变换方法对动力响应进行数值求解,详细分析了硬壳层厚度、模量和泊松比对动应力扩散作用的影响。研究结果表明,软土地基表面的动力响应对硬壳层厚度和模量的变化十分敏感,硬壳层的存在大大地减弱了软基顶面的竖向动应力,并且增大了竖向动应力的分布范围,可见硬壳层对交通荷载引起的动力响应有明显的扩散作用。     

高填石路堤动力响应的室内模型试验及弹塑性有限元分析

高填石路堤在工后运营过程中,长期受到动力荷载的作用。基于相似比理论建立高填石路堤动力响应的室内试验模型,以简谐振动荷载和冲击荷载模拟高填石路堤实际受到的复杂动力荷载,采用动土压力盒和加速度计拾取模型路堤在振动器作用下的响应波形,利用Drucker-Prager弹塑性本构模型进行模型路堤的动力响应有限元分析。分析结果表明,有限元分析值与实测值比较接近,即使在较大的动力荷载作用下,高填石路堤内部产生的塑性区也只是暂时的和局部的,仍可维持其整体稳定,且表现出应变硬化的动力特性。     

山区公路典型沥青路面结构容许横向沉降差研究

大量的研究表明,路基不均匀沉降导致上部路面结构在车辆重复荷载作用下出现早期的破坏,严重影响了路面服务性能,而现有的路面结构设计未考虑路基不均匀沉降对路面结构的影响。在以往对路基不均匀沉降研究的基础上,采用有限元程序ABAQUS分析了在路基发生不均匀沉降条件下,路面承受车辆重复荷载作用的动力学响应以及路面开裂的变化过程,引入损伤变量定量描述了路面的破坏过程,分析了路基横向沉降差对路面开裂的影响,并参照路基边坡稳定安全系数的定义及规范取值。在此基础上,提出了山区公路典型沥青路面结构的容许横向沉降差值为2.2‰,并建议将其作为路基路面结构整体设计的一个控制指标加以考虑,以避免路基不均匀沉降导致的路面早期破坏,从而提高山区高等级公路的设计及建造水平。     

地震荷载下风积沙路堤动力响应规律

为了研究风积沙路堤在地震动荷载下的动力响应规律,设计和制作了模型路堤并进行振动台试验,通过对模型中埋设的多个加速度传感器和位移传感器记录的数据进行分析,得出风积沙路堤模型在动荷载作用下的动力响应规律。得出如下结论:模型路堤对输入的地震波具有明显的放大作用,加速度反应放大系数PGA随着竖直高度的增加显著增大;在路堤内同一高度沿水平坐标的增大放大效应变化不明显或稍有增加;当控制地震波波形和强度相同时,边坡坡率越大PGA放大效应越明显;另外,风积沙路堤的阻尼比、自震频率、动模量等参数随着动荷载作用历史的变化而变化,从而进一步影响风积沙路堤加速度响应的频谱特性。研究风积沙路堤在动荷载作用下的动力响应,可以为沙漠地区高填方路堤抗震设计提供技术支持。     

考虑非饱和路基性能劣化的路表振动响应研究

为了给应用落锤式弯沉仪（falling weight deflectometer,简称FWD）准确识别路基性能劣化提供理论基础,建立了考虑路基非饱和特性的弹性层状路面在FWD荷载作用下的振动响应计算模型。通过Laplace-Hankel变换对模型的动力控制方程进行了推导求解,建立了路面和非饱和路基的动力刚度矩阵。并由层间连续性条件合成了公路结构的整体动力刚度矩阵,结合边界条件得出了FWD荷载作用下整个公路结构在变换域内的振动响应解。利用Laplace-Hankel逆变换对振动响应进行了空间-时间域内的数值求解,分析了FWD荷载频率和路基饱和度对振动响应的影响以及路基性能劣化与路表振动信号的关联性。研究结果表明：路表竖向动位移主要受FWD荷载低频成分的影响且随饱和度的增大而增大;相比较路表振动速度和路基表面竖向动应力,路表竖向动位移受路基性能劣化的影响更敏感,且在距荷载中心1.2 m位置处的路表竖向动位移变化率达到最大。研究结果可为路基性能劣化的反馈指标与位置选择提供科学依据。     

交通荷载作用下公路路基工作区深度研究

根据路面不平整实测资料,获得了汽车动荷载的计算模型和参数,并利用此荷载模式来分析公路结构的动力响应。考虑到公路结构的三维分层性状,利用Fourier变换技术和求解层状结构的精确刚度矩阵法,研究了公路结构在移动汽车荷载作用下的动力响应问题。为了方便工程应用,利用Odemark厚度和模量的当量转换公式,将公路结构简化为由路面、路基及地基组成的3层体系,并以此为基础分析了路基动应力的衰减规律,同时重点研究了汽车轴载大小、当量路面厚度及路基模量对路基工作区深度的影响,最后建议了路基工作区深度的定量表达式,研究结果可为公路路基设计提供参考。     

离岸深水全直桩码头动力简化计算方法研究

离岸深水全直桩码头结构长期承受波浪力、撞击力等动荷载作用,仅从静力角度分析不能满足工程设计要求。为研究离岸深水全直桩码头结构动力简化计算方法,利用ABAQUS软件建立了全直桩码头的嵌固点模型和结构-地基相互作用的三维弹塑性有限元模型。基于所建立的有限元模型,采用模态分析法研究了上述码头结构的自振特性。分析表明,结构基本周期较长,与波浪力、撞击力荷载周期接近,结构动力响应突出。进一步计算发现,全直桩码头结构在波浪力、撞击力荷载作用下的动力响应有限元计算结果与采用单自由度系统位移动力放大系数理论公式计算结果吻合较好,由此提出全直桩码头结构动力响应可按单自由度系统位移动力放大系数理论公式进行简化计算。在此基础上,结合规范中的m法、p-y曲线法、NL法提出了上述码头结构动力简化计算方法,通过与动力有限元计算结果对比,验证了所建立简化计算方法的正确性。     

交通荷载作用下Kelvin地基上不平整路面的动力响应分析

为了评价不平整路面在交通荷载作用下的动态响应,从路面几何不平整出发,假设路面不平整服从正弦函数曲线,并把1/4车身结构简化为2个自由度振动体系,得到了不平整路面上的动荷载表达式。又将此荷载模式看成是作用在Kelvin地基上无限大路面板表面的移动矩形荷载,采用双重Fourier变换方法得到了不平整无限大路面板竖向位移的积分形式解,此解析解可以退化为静荷载作用下的经典解答。并利用快速傅立叶变换(FFT)方法得到了数值计算结果。分析了荷载速度,路面不平整波长、不平整幅值以及地基阻尼和地基刚度对板的动力响应的影响。结果表明,板竖向位移的分布受荷载移动速度的影响;位移幅值随着路面不平整波长和荷载速度的变化出现2个峰值;路面不平整使得位移峰值出现滞后现象,且不平整波长越小或不平整幅值越大,滞后现象越明显。     

Effect of vehicle–pavement interaction on dynamic response of rigid pavements

In the present paper, dynamic response of rigid pavements subjected to moving vehicular loads is presented using an analytical procedure based on the finite element method. The vehicle–pavement interaction effects are taken into account while developing the solution algorithm. The concrete pavement is discretized by finite and infinite beam elements. Infinite elements are helpful in appropriate modeling of end conditions. The main purpose of the development of infinite elements is to model the unbounded domain. The underlying soil medium is modeled by Pasternak model which assumes the existence of shear interaction between the spring elements. The moving vehicle is represented by a mass supported by a spring-dashpot system. The vehicle -pavement interaction force is modeled with Dirac-delta function. Dynamic equilibrium equation is solved with Newmark-Beta integration scheme. It has been observed that the dynamic interaction between the moving load and the pavement has significant effect on pavement response. Parametric study is carried out to investigate the effect of vehicle–pavement interaction (VPI) and soil parameters on the response of pavement.     

Numerical Analysis of Asphalt Pavements under Moving Wheel Loads

INTRODUCTIONThe design methods of asphalt pavement areusually based on the static and elastic analysis sys-tem,though the actual loads such as wheel loads andtemperatureloads are kinetic.The mechanic responseof the pavement is sensitive to the ti me-dependentvariables.Thereis an obvious difference betweentheresults obtainedfromthe kinetic systemandthe stat-ic system.Thus,the dynamic analysisis necessarytodescribe explicitly the working condition of the as-phalt pavement.The dynamic charac…     

A combined method to predict the long-term settlements of roads on soft soil under cyclic traffic loadings

In order to investigate the mechanism of the long-term settlement of road on the soft soil, an in situ measurement of a highway in southeast China was conducted during both the construction and post-construction stage. In the theoretical analysis, the long-term settlement of the pavement on thick soft soils was divided into three main components: the consolidation settlement, the creep deformation and the traffic load-induced deformation. The equivalent time line model based on the viscous–elastic–plastic theory was adopted to simulate the road settlement caused by the consolidation and creep of the subsoil. A cyclic strain accumulation model, which was obtained from laboratory tests of soil elements, was adopted to consider the road settlement induced by cyclic traffic loadings. A pavement dynamic response model was used to calculate the dynamic stresses in the subsoil generated by moving traffic loads when the road was open to service. It was found that the equivalent time line model combined with the cyclic strain accumulation model could predict the road settlement accurately at both the construction and post-construction stage. Numerical results showed that the traffic speed had limited effect on the post-construction road settlements for the speed range considered. The post-construction settlement of the road, mainly composed of the traffic-induced settlement and soil creep deformation, could be reduced significantly by increasing the embankment surcharge during the construction stage. The creep component accounted for over 10% of the total post-construction settlement, while the percentage of the creep deformation in total post-construction settlement decreased rapidly as the embankment surcharge increased.     

高速公路路基结构分析及动变形设计方法

考虑汽车运动荷载,基于实测路面不平整资料,对影响动荷载的因素进行分析,提出了动力设计荷载参数的建议值。通过Odemark模量和厚度当量假定,将公路结构简化为3层体系,并利用弹性动力学原理及Fourier变换方法获得了路基顶面动变形的计算式。结合现有规范关于路面弯沉控制的思想,考虑路面路基的相互作用及协调变形,给出了路基顶面的动变形控制标准和确定方法,依据此标准提出了一种路基动变形控制设计的方法。最后以3种典型沥青公路结构为例,进行了路基动变形控制设计。     

Modelling of rutting of two flexible pavements with the shakedown theory and the finite element method

This paper presents a finite element program, for the modelling of rutting of flexible pavements. In its present version, the program incorporates a permanent deformation model for unbound granular materials based on the concept of the shakedown theory developed by Zarka for metallic structures under cyclic loadings and has been used to estimate the permanent deformations of unbound granular materials (UGM) subjected to traffic loading. The calculation is performed in two steps: the first step consists in modelling the resilient behaviour of the pavement in 3D, using non-linear elastic models, to determine the stress field in the pavement. Then stress paths are derived and used to calculate the permanent deformations and the displacements, using a Drucker–Prager yield surface. An application to the prediction of the permanent deformations of experimental pavements with an unbound granular base, tested on the LCPC pavement testing facility is presented.     

预应力锚索桩板墙动态响应规律研究

随着公路交通流量增加及超载车辆增多,交通荷载对支挡结构的受力变形特性影响越来越大。通过FLAC3D软件建立预应力锚索桩板墙空间分析模型,并与现场动应变测试结果进行比较,探讨了交通荷载作用下挡墙的受力变形机制。结果表明：交通荷载在路基与挡墙中所反映的影响深度大致都为2 m左右,正常情况下（重型汽车满载、行驶在行车道上）作用在预应力锚索桩板墙上的动土压力大约为该处挡墙静止土压力的10 %。     

The use of the equivalent single wheel load concept for discrete raft type pavements

With the increasing use of 2 meter square discrete raft type pavements to replace insitu concrete pavements and flexible pavement materials; it became necessary to assess the infinite pavement assumption, that an equivalent single wheel load could be used to represent the actual multiple wheel loading for pavement analysis. By carrying out a computer analysis the authors found that the raft pavement stresses varied according to the actual multiple wheel load and its position on the raft. Two series of laboratory experiments confirmed the computer results and showed that the concept of a single wheel load equivalent to the multiple wheel load considerably underestimated the pavement's life and should not be used for discrete raft type pavement design.