FEM Simulation On Rubblization Process Of Concrete Pavements And Overlay Structures

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.