Study On Mechanics Behavior Of Double Layer Concrete Pavement

Base on the practice in recent years indicates that the additionally paved cement concrete pavement often occurs the phenomenon of delamination on interlayer and broken slab early. However, emphasis from the influence of construction of early age, the paper based on field test of full-scale slab, numerical simulation and theoretical research methods to study on mechanics behavior of double layer concrete pavement. So the research conclusions is revealed as follows.Firstly, based on numerical simulation technique, the temperature field characteristics of a double layer board in early age were analyzed. the results show that the primary factors affecting early-age temperature field and temperature gradient of double layer board are panel thickness, curing methods and solar radiation intensity, and secondary factors include wind speed, thermal conductivity, paving time, solar radiation absorption rate and the water-cement ratio. The results also indicate that positive temperature gradient of set the sandwich double layer board is less than the combinational pavement, while the negative temperature gradient is on the contrary. Combined with the results of the sensitivity analysis of the temperature of construction, proposing the temperature control measures for construction of the double layer board.Then using finite-element program to analysis temperature stress of the double layer board when considering the curing temperature. The results show that the curing temperature have a significant impact on the temperature stress of the double layer board, and the adverse combination of curing temperature of the double layer boards. From the analysis of different thickness of the additionally paved pavement, the temperature stress increased first and then decreased with the increasing of the thickness, and the sensitive thickness of upper panel of the double layer board is 18cm, the temperature stress of combined additionally paved board was larger than flexible sandwich layer board.Thirdly, analysis the void and mechanical impacts of combined double layer board cased by curing temperature during the early age and the stage of operation period, the result indicate that overlay pouring at different time, it is widespread inter-layer void at plate angle of the double layer board after pouring 12h, the void which is poured at 7:00 is the most significant, and it also appear early cracking during the period. The additionally paved board will appear premature off-board phenomenon when considering the combined effect of the vehicle and temperature in the operation period. At the same time, contrasting the mechanical behavior of setting asphalt sandwich layer board and combined additionally paved board, the former bears relatively small force, so setting asphalt sandwich layer board is recommended.Besides, based on the analysis of the mechanical and fatigue properties of the sandwich layer board, which is under combined effect of curing temperature, the temperature and moving dead load, the result show that the worst load position of the additionally paved board which will tilt upward and down is in the middle and angle of the plate, the vehicle running along the edge of the board is the most adverse.When the shaft type is single axis with two wheels, the lager the axle load and downward warpage of old board, the more adverse to the additionally paved board. The amount of warpage have a significant impact on the the fatigue life of the additionally paved boar, and secondary factors include axle load, plate size, paving thickness, shaft type,thickness of the sandwich and the bending tensile strength of additionally paved layer.At last, studies have shown that the amount of warpage will reduce by means of choosing the appropriate time of paving, sprinkler maintenance, the initial temperature of concrete, cement type, water-cement ratio and aggregate, thus, improve the life of the additionally paved board effectively. Secondly, by limiting the axle load of the the vehicle, reducing the length and width dimensions of board, increasing plate thickness,improving panel bending strength can also improve the life of the additionally paved board, so the setting asphalt sandwich layer board is the preferred choice.