【作者】 张泉；

【导师】 陆阳；

【作者基本信息】 西南交通大学 ， 道路与铁道工程， 2011， 博士

【摘要】 近年来,随着对修复或加铺旧水泥混凝土路面需求的快速增长,解决加铺层所涉及的关键技术和工程问题以及节约工程投资、提高效率、保证行驶质量,显得非常迫切。而旧水泥混凝土路面改建技术的关键,是对破损混凝土路面板的处理方法。水泥板碎石化方法是将旧水泥混凝土板块破碎后作为改建路面的基层或底基层,较好地利用了原混凝土板的强度,不仅节省投资、有效地防治反射裂缝的产生或发展,而且有效地解决了废料的处置问题。碎石化技术虽在国内工程实践中有所应用,但仍不成熟,工程界对旧水泥路面碎石化加铺层设计方法尚未取得共识,相关的力学机理、加铺层设计理论、路面设计及验收指标的选取、破碎层特性的表征等仍需做大量的研究工作。鉴于此,论文将在广泛调研的基础上,结合成绵高速公路改建工程,通过理论研究与数值分析、室内外试验等技术手段,对碎石化沥青加铺结构相关力学行为特性进行研究。首先,根据现场试验路的试验分析,研究碎石化层的材料特性和结构性能。通过现场调查、钻芯取样、开挖检查坑等手段,获得了碎石层的级配等基本物理参数。研究中,根据弯沉等效原理,对FWD弯沉检测值进行了反演分析,确定路面各结构层的回弹模量值。由于路表弯沉实为路面各结构层对荷载作用的综合响应,其中又以路基的竖向变形所占比例最大,因而反演过程中,根据结构层内荷载扩散规律,采用了由远及近、分步反演的方法,即先由远离承载板的弯沉值反算路基模量,再由承载板附近的弯沉值反算路面各结构层的模量。考虑到路面结构在FWD动载作用下所表现出的力学响应行为不同于静载,论文在大型有限元软件ABAQUS的平台上,应用python语言二次开发了动力有限元的反演程序,对碎石化前、后成绵高速的路面改建工程检测数据进行反演,得到了与现场实际情况较为接近的路面各结构层力学参数。在实体工程检测数据分析的基础上,选取两典型的碎石化沥青加铺结构(碎石化加铺结构1中旧混凝土上层破碎粒径≤15cm,碎石化加铺结构2中旧混凝土上层破碎粒径≤7.5cm)进行室内沥青加铺层足尺疲劳试验。在控制环境及荷载条件下,重点研究竖向动荷载累计作用所引起的沥青加铺层及下卧碎石层力学状态的变化,探讨碎石层物理指标与加铺层结构劣化的关系。试验结果证实了沥青加铺层层底应变随荷载重复作用次数增长呈现增加趋势；同时发现,相同环境及荷载作用下,加铺层层底应变增长率与旧混凝土层的碎石化程度有直接的关系,碎石化程度较低的加铺层结构(结构1)的应变变化率明显大于碎石化程度较高的加铺层结构(结构2)应变变化率,说明在基层承载力得以满足的情况下,适当提高旧混凝土路面的碎石化程度将有利于加铺层结构的抗疲劳性能。为进一步认识碎石化程度对沥青加铺层力学行为特性的影响,建立了混凝土碎石化路面沥青加铺结构计算模型,模型视沥青加铺层、基层及土基为连续介质,旧混凝土碎石层为离散介质,分别采用有限差分和颗粒离散元加以模拟,并通过界面的强制性连续条件,实现有限差分和颗粒离散元的耦合。根据现场检测情况,将破碎混凝土简化成三层,即碎粒层、碎石表层和碎石底层,通过模拟计算,探讨不同尺度材料组合情况下的结构计算方法。结果表明,碎粒层分层厚度越厚,旧混凝土板碎石化程度越高,沥青加铺层底承受的拉应变、拉应力和荷载中心作用处的弯沉也就越大。当碎粒层颗粒粒径由1mm变化到2mm时,沥青加铺层底的拉应力、应变也相应变大；而碎石表层颗粒粒径由5～8mm减小到3～5mm,即旧混凝土面层破碎越碎,原水泥混凝土面板的强度下降的越多,整体性也就越差,沥青加铺层底的拉应力、应变也就越大。计算结果证实,说明在施工过程中,破碎混凝土块的粒径应控制在一定的范围内。针对旧水泥混凝土路面碎石化后加铺沥青面层这类特定的复合结构形式,分别以路表弯沉和结构层底容许拉应力为控制指标,在2D有限元通用计算程序的平台上,进行了典型路面结构可靠度计算和灵敏性分析程序的二次开发,并通过计算,确定了对碎石化沥青加铺结构可靠性影响较为显著的因素。计算结果表明,以容许拉应力为控制指标对路面结构可靠度指标的影响大小依次为：土基、碎石层、基层与沥青面层。其中,土基和碎石层对结构可靠性指标的影响占到85%以上,是结构抗拉性能的决定性因素；另一方面以路表弯沉为控制指标对路面结构可靠性指标的影响大小依次为：加铺层、基层、土基与碎石层,其中,加铺层和基层的模量对结构可靠性指标的影响占到90%以上,是路面抵抗弯沉变形的决定性因素。因此,碎石化沥青加铺结构设计和施工过程中应综合考虑这两方面因素,寻求平衡点,达到路面结构对荷载响应的整体性最优。更多还原

【Abstract】 In recent years, with the rapid growing of the demands of the rehabilitation and asphalt overlays over PCC pavements, it turns out to be urgent for how to solve the key technical problems and engineering issues, improve the functional pavement performance and ensure the quality of driving when considering save the investment. However, the key technology of the reconstruction of the old cement concrete pavement is the treatment method of the damaged concrete slab. Rubblization of PCC pavement is an optional technique to rubblize the slab into fragments, which includes transforming the original concrete slabs into an aggregate base or subbase. It’s better to use the structural capacity of the existing pavements, which not only reduces the investment and effectively eliminates the reflective cracking, but also solves the waste disposal problems. Although the rubblization has already been applied in the domestic engineering, it’s still need to refine and has not yet reached a consensus on the design method of asphalt overlays over PCC slabs under heavy traffic load. So there’s much research work need to be done, such as the mechanical mechanism of rubblizing PCC pavement, the design method of AC overlays, the properties and pavement performances of the rubblized layer, etc. In this work, through theoretical research, numerical analysis, indoor and outdoor tests and other means, the mechanism behavior of the asphalt overlay over the rubblized PCC slabs is discussed compound with the extensive research and Chengdu-Mianyang highway reconstruction projects.At first, this paper carries out reseach on the properties of rubblized layer by the means of field investigating, core sampling and test pits excavating. It obtains the basic physical parameters and the gradation of rubblized layer. The resilient modulus of pavement materials has been backcalculated through the FWD testing data of experimental roads,according to the deflection equivalence principle.The surface deflection is actually a comprehensive response to the load, and the maximum proportion of the vertical deformation is caused by the subgrade. So, according to the load diffusion law, the backcalculated process of modulus is that the modulus of subgrade is first back calculated on basis of the deflection, which is away from the bearing plate. Then the modulus of the other structure layer of pavement is back calculated on the basis of the deflection near the bearing plate. Because it’s the difference the mechanical response under the FWD dynamic loading from that under the static load, the measured FWD data that pre and post rubblization is used to back calculate the parameter of pavement materials using the finite-element software of ABAQUS, which is applied to secondary developed of using the python computer language, combined with Chendu-Mianyang highway reconstruction projects.The results suggest this program can give rational mechanical parameters of pavement structure.Then, combined with the actual conditions on site, two typical structures of asphalt overlays over the rubblized PCC slabs, which the broken particle size of the structure 1 is less than 15 cm, while the broken particle size of the structure 2 is less than 7.5 cm, is selected to carry out the full-scale fatigue experiment. The changes of the mechanical condition of the asphalt overlays and rubblized layer is studied, caused by the cumulative effect of the vertical dynamic loads. Meanwhile, the deterioration relationship between the physical indicators of the rubblied layer and overlays is discussed under the control of the environment and load conditions. The results show that the strain response of pavement varied with the load conditions.And the strain with load repetition has shown an increasing trend. The strain rate at the bottom of asphalt overlays varies with the particle size of the rubblized layer under the same load.The strain rate of the pavement structure 1 is 0.9119,which is larger than 0.3564 of the pavement structure 2. It indicated that the particle size has great influenced on the fatigue property of the alphalt overlays.To understand how the characteristics of mechanical behavior is affected by the degree of rubblization slabs, a numerical method which combines the finite difference and DEM is proposed, in which the rubblized PCC slab is described using DEM while the asphalt overlays, base and subgrade is simulated by the finite difference method, according to the actual structure. The conditions of mandatory continuity along the corresponding boundaries need to be satisfied in the computation process. To illustrate the effects of rubblization on asphalt overlays pavements more clearly, rubblized PCC slabs is further divided into three sublayers as the small particles layer, the surface layer and bottom layer. The calculation methods of material combination of different scales are discussed. The results show that the thicker the small particles layer is, the higher the degree of rubblization of the slabs is and the larger the tensile stress, strain and deflection at the bottom of the asphalt overlays are. It also found that the particle size of a small particles layers is increased about 1mm to 2mm, the tensile stress and strain at the bottom of the asphalt overlays are proportional to the particle size of the small particles layer; while the particle size is reduced from 5-8mm to 3-5mm, the smaller the particles size of the surface layer is, the higher the degree of rubblization of the slabs is and the larger the tensile stress and strain are. In other words, strength loss of the old PCC is proportional to degree rubblization of the slab. This shows that the degree of rubblization should be properly controlled in the reconstruction projects.Finally, combined with the actual structure of asphalt overlays over the rubblized PCC slabs, the significant factors affect the reliability of the asphalt overlays over the rubblized PCC slabs are determined. The two state equations are established in which the design deflection and the allowable tensile stress at the bottom of the asphalt layer are determined as the main index respectively. And the program of the reliability and the sensitiving analysis of the pavement structure is the secondary developed in the 2D finite element computer program platform.The results show that the factors which affect the reliability of the structure of pavement are as fellows:subgrade, the rubblized layer, base and asphalt overlays,according to the allowable tensile stress at the bottom of the asphalt layer. Among them, the factors of the subgrade and the rubblized layer are more than 85%,which are the decisive factor of the resistance to tensile strength of the structure.While the factors which affect the reliability of the structure of pavement are as fellows:asphalt overlays, base, subgrade and the rubblized layer, according to the surface deflection; Among them, the factors of the asphalt overlays and baser are more than 90%,which is the decisive factor of the resistance to deformation of the surface deflection. Therefore, seeking a balance in order to achieve overall optimum to the performance of the pavement structure under the load, two main factors which affect the reliability of the structure of pavement should be taken into account,comprehensively,in the design and construction.更多还原