The Research On The Deflection On The Edge Of The Joint Of The Existing Cement Concrete Pavement And Its Effect Factors

Compared with asphalt pavements ,the rehabilitation of the cement concrete pavements are relatively difficult .The commonly most used measure is to pave asphalt concrete on the old cement concrete road surface. This measure is not only convenient , but also dramatically improving the serviceability of the old pavements. There are many joints and cracks in the existed cement concrete pavement paved with AC overlay where too much deflection and deflection difference will take place as vehicles pass through and then to cause the appearance of reflecting cracking. Reflecting cracking itself hasn' t much effect on the performance of the asphalt concrete overlay, but water will enter into subgrade as soon as reflecting cracking appears. The water will not only erode subgrade and cause pumping , but also decrease the supporting capacity of the pavement.Under the pressure of load , the deflection and deflection difference near the joint relate to a lot of factors. In the paper the ability of transferring load , supporting capacity of the foundation and the condition of existing void are taken into account . The old cement concrete pavement is simplified into a beam on the winkler foundation and a theorical formular is got which is used to calculate the deflection value near the seam .In order to discover the relationship between the results got from the two-dimension theorical formular and the three-dimension FEM model, the three-dimension model is created. The results show that the deflection got from the two-dimension theorical formular is many times larger than the deflection from the three-dimension FEM modle . At the same time ,the effect factors are analyzed.