【作者】 龙兵；

【导师】 黄立葵；

【作者基本信息】 湖南大学 ， 道路与铁道工程， 2010， 硕士

【摘要】 多锤头碎石化是一种旧水泥混凝土路面处治技术,具有工期短、环保、节能、性价比高等优势,在旧混凝土路面改建中应用十分广泛。采用碎石化技术处理混凝土路面,加铺沥青混凝土面层,是目前水泥混凝土路面改造技术研究和发展的一个重要方向。但是,目前国内外对碎石化技术的研究多局限于施工经验,理论研究尚显不足。对碎石化过程的有限元模拟一般都采用拟动力弹性模型分析,即将冲击荷载用动量定理反算冲击力,再将该力作为静止荷载作用在路面结构上,或者定义一个函数曲线,假定荷载按该曲线随时间变化。本文将模拟锤头在自重作用下,以一定速度冲击混凝土板,进行三维动力有限元模拟,考虑到混凝土板破碎时,内部应力已经超过弹性范围,因此结构层材料采用非线性模型模拟更接近真实情况。对于路面加铺结构的受力分析,以前的研究也多采用静止荷载,因移动荷载更符合实际情况,故本文采用移动均布荷载来模拟行车荷载。混凝土路面碎石化后试坑开挖及施工控制不当等因素会使碎石化后顶面回弹模量变异较大,对加铺后路面受力不利,本文将分析碎石化后顶面回弹模量突变对沥青加铺层的影响,并提出改善措施。本文采用有限元模型进行分析,主要取得了如下研究成果：(1)建立了三维非线性动力有限元模型,混凝土材料采用损伤塑性本构模型模拟、基层和土基采用Drucker-Prager/Cap修正塑性本构模型模拟,荷载为重锤做自由落体运动,以一定速度冲击混凝土板,分析了四种典型工况下,混凝土板的变形、受力及破坏特征,以及冲击过程对基层和土基的影响。(2)用三维非线性动力有限元模型分析了下落锤头的个数、锤头落点间距、锤头下落高度、基层模量、土基模量、层间接触、混凝土板和基层厚度等因素对冲击破碎过程的影响；拟合了锤头下落高度与板底横向弯拉应力的关系式。(3)用三维弹性动力有限元模型分析了移动荷载下,碎石化层顶面模量突变对沥青加铺层受力的影响。(4)用三维弹性动力有限元模型分析了移动荷载下,碎石化层模量突变对沥青加铺层反射裂缝及从上往下裂缝应力强度因子的影响。更多还原

【Abstract】 Multiple-Head-Break Rubblization is one of treatment methods of existing PCC pavements. This technology has many advantages which includes short construction period, protecting the environment, energy saving, high performance-to-price ratio and so on. So it is widely applied. The technology which treats the existing concrete pavements and overlays the layer of asphalt concrete is an important direction of research and development in our country at present.But the research on rubblization limits much to the construction experience and the theoretic research are still obviously insufficient. The previous researchers have used static loads to simulate dynamic loads. Some researchers use Momentum theorem to deduce the impact force and then put the impact force as a static load on the pavement. Another researchers define a function curve and add the load to the pavements according to the function curve. The hammer which has a definite velocity impact the concrete slabs was simulated in thesis. It is a three-dimensional dynamic nonlinear Finite Element Model. Because the stress of concrete slab is beyond the linearity range when the slab is fragmentized, nonlinear material model was used in this thesis. Many researchers also use linearity Finite Element Model about the static load to study the stress of pavement structure, but the moving load is more tally with the actual load. The influence about modulus variation to the overlays’stress was analyzed in this thesis and then some methods which could decrease the influence were proposed.In this thesis these research findings were obtained:(1) A three-dimensional nonlinear Dynamic Finite Element Model was established. Concrete damaged plasticity model was used to analyze the concrete material. Drucker-Prager/Cap plasticity model was used to analyze the base and the subgrade. The hammer with a definite velocity impacted the concrete slabs. The displacement, stress and damage of concrete under the impact loads was analyzed in thesis. The influence of base and subgrade was also analyzed.(2) The FEM model was used to analyze the causes which influences the impact effect. The causes including the number of hammers, the distance between hammer drop site, the height of hammers, the base modulus and subgrade modulus, the contact between the layers, the thickness of concrete slab and base, et al. At last, we obtain a formula about the drop height of hammer and the lateral tension stress which at the bottom of the concrete slab.(3) The influences about modulus variation to the overlays’stress was analyzed in this thesis.(4) The influences about modulus variation to the stress intensity factor of overlays’reflection cracks and Top-Down cracks was analyzed in this thesis.更多还原