【作者】 刘振新；

【导师】 陆阳；

【作者基本信息】 西南交通大学 ， 道路与铁道工程， 2011， 硕士

【摘要】 在旧水泥混凝土路面上加铺沥青混凝土面层,是将其改造成沥青路面的一种比较经济的方式,无论是在公路还是在城市道路改造中采用得都比较多,尤其是随着我国石油工业的发展,沥青产品质量提高,国产石油沥青满足道路规范要求,目前有很多的旧水泥混凝土路面因使用年限较长,路面状况恶化,需要进行改造。水泥混凝土路面上加铺沥青面层快速、经济的优点就体现出来,越来越多的地方选择加铺沥青面层的改造方式。疲劳损坏是沥青路面特别是柔性基层沥青路面的主要破坏模式之一。因此,多年来,沥青路面的疲劳特性一直是路面工程研究的重点。本文在前人研究的基础上,通过不同碎石化程度下,室内沥青加铺结构足尺模型疲劳试验,分析了沥青层底荷载动态响应特性,并对试验结果进行了初步分析,主要包括：(1)室内足尺结构模型试验为在可控环境下,研究混凝土碎石化沥青加铺层结构的荷载疲劳特征搭建平台,而试验的基础是合理构建能反映客观实际的结构模型。考虑到碎石化的技术要求与施工工艺之间的密切联系,根据试验场地的实际情况,在气锤破碎混凝土的基础上,采用振动压实,对碎石混凝土进行了二次破碎整形。构建模型的过程表明,基于气锤破碎与振动压实的混凝土路面碎石化,通过破碎参数的合理选择,完全可以得到与公路基层规范的要求相符的粒料柔性基层。(2)模型试验应在不违背结构基本特性的前提下,在贴近实际与简化问题之间寻求平衡。由于沥青混合料所具有的粘滞性,加铺层结构的荷载响应具有明显的时间滞后效应,因此常规的应力、应变测试方法难以应用于路面加速疲劳试验中。为此,设计、采用了以静态间接测试为主、动态直接监测为辅的测试系统,满足了试验分析对数据采集量的需求。(3)作为粘弹塑性材料,沥青混合料的粘滞性显著影响加铺层对动荷载作用的变形响应,而以碎石化混凝土为基层时,加铺层结构对动荷载的力学响应显得更为复杂,不仅与测点所在位置有关,也与荷载水平有关。在荷载板直接作用区域以外,平行于板长边方向受拉,而垂直于板长边方向则可能受压；在荷载板直接作用区域内,当动荷载幅值为25KN时,加铺层层底始终处于拉应力场内；而动荷载幅值增至50KN时,加铺层层底则因回弹,处于拉-压应力交替作用状态,加速了加铺层疲劳破坏的演化进程。(4)以碎石化混凝土为基层的沥青加铺层结构,在竖向荷载作用下,明显表现出柔性层状结构的特征。从试验结果看,荷载板直接作用范围内,加铺层层底拉应力显著大于荷载板以外的层底拉应力,而且距离荷载作用区域越近,应变响应越明显。尤其值得注意的是,荷载板以外的各测点处,拉应变随累计荷载作用次数的增加而增长的量微乎其微,但在荷载中心处,不仅拉应变随荷载作用次数的增加而增大,而且拉应变的增值率也呈增大的趋势。(5)混凝土面板的碎石化程度是决定加铺层结构功能重要因素。在相同荷载水平及作用次数前提下,碎石化程度较高的加铺层结构层底最大拉应力小于碎石化程度较低的加铺层结构层底最大拉应力,而且更应引起注意的是,就加铺层层底非恢复拉应变而言,碎石化程度低的结构的拉应变增长率也显著高于碎石化程度较高的结构,因此碎石化程度高的结构的抗疲劳性能优于碎石化程度低的结构。更多还原

【Abstract】 The existing cement concrete pavement with asphalt concrete over lay is the economical and fast way widely used in the highway or the reform of urban roads transformation in the new situation with the domestic oil industry rapid developed, and the product quality improved to conform the specifications, which promotes the improvement for the damaged cement concrete pavement used for number of years. For many years, the fatigue failure has been the focus of pavement engineering research as the major failure factor. Therefore, on the basis of previous studies, this paper analyzes the fatigue test of asphalt layer base load dynamic response characteristics and makes the preliminarily analyzing on the experimental results, through the experiment for fatigue of add a store structure of the full-scale model indoor in different rubblization degrees of asphalt, mainly including:(1)The full-scale structure model indoor test loads with a platform for the stress analysis of concrete rubblization asphalt overlay under the controlled environment, which is based on a reasonable model reflecting the objective reality. Considering the close relations between the technical requirements of rubblization and construction craft and according to the actual situation of experimental sites, vibrating compaction is adopted to make the secondary crushing plastic based on the pneumatic hammer broken concrete. The process of constructing mode indicates that the rubblization pavement based on the vibrating compaction and the pneumatic hammer can be completely with highway grassroots specification correspondence of aggregates flexible grassroots through the rational choice s.(2)Model test seeks a balance between under the precondition of practical and simplify the questions without violating the basic characteristics of structure.Due to the asphalt mixture with viscosity which makes time lag effect significantly on the stress response on the pavement overlay, the conventional stress and strain test methods cannot be used in accelerating fatigue test on the pavement. Therefore, designing of directly monitoring subsidiary, a static indirect test, dynamic test system satisfies the experimental analysis of demand for data collection capacity.(3)As the viscoelastic plastic materials, the viscosity of asphalt mixture significantly influences the deformation response of overlay, so with rubblization for grassroots, the response of overlay structures to the dynamic loads even more complicated not only with the location with load level related, also concerned. Out of the load plate direct action area, the long side direction parallel to the plate may be in the tensile while the side perpendicular to the plate may be compression; in load plate direct area, when amplitude for dynamic loads being 25KN, the bottom of pavement in the layer within the pull stress field; and amplitude for dynamic loads being 50KN, layer being in the state of alternative action of pulled compressive stress because of rebound, accelerating the overlay fatigue damage evolution process.(4)The overlay structures with rubblization concrete as grassroots obviously display the flexible layered structure characteristics under vertical stress. From the experiment results, the tensile stress of the bottom of pavement in load plate direct area is significant higher than outside the plate, the distance closer the more obvious strain response. Especially, the point monitored outside the load plate, tensile strain quantity increases very little with the increasing of accumulation of loads, but in load center place not only tensile the strain quantity increases with the numbers of load also the tensile strain rate shows the increase trend.(5)The rubblization degree of concrete slabs is the important factors to decide the function of the overlay structure. In the same load level and action frequency premise, the maximum tension stress on the bottom of overlay structures with high rubblization degree is less than low rubblization degree, and more attention should be paid to that concerning the unrecoverable tensile strain at the bottom of pavement overlay, the tensile strain rate with high rubblization degree increases significantly higher low rubblization degree. Above all, the fatigue resistance with the structure of high degree of rubblization is better than the structure of low degree.更多还原