Study On The Pavement Structure Of Shaoyang Rebuilt And Expanded Municipal Roads

With the rapid development of our economy and society and the advancement of urbanization, urban vehicle ownership in the rapid growth, increasing pressure on municipal road traffic, urban traffic congestion problems have become increasingly prominent. Due to the acquisition of urban land is difficult, it is usually difficult to build new roads in the urban area. It is an effective measure to promote the traffic service capacity of urban roads by reconstruction and expansion of the urban municipal roads to widen the roads and improve the quality, which will be increasingly applied to pratice.Since the construction has great effect on its surrounding traffic and environment, and with the more demanding schedule requirements, therefore, on the condition that the difference settlement between new and old subgrades can not be avoided, then in order to improve the economic viability, using which way to broaden the roads, to promote the performance of the pavement structure and enhance the life of the reconstruction and expansion roads, which has great important significance.Shaoyang City belongs to the climatic zoning with humid and rainy climate, big temperature differences in summer, large temperature differences between days and nights. After investigating the current situation of Shaoyang municipal roads’ reconstruction and expansion project and the road surface diseases, it is concluded that there may exist five possible construction solutions. For different reconstruction and expansion solutions, there were respectively established finite element models, to have the sensitivity analysis and the stress analysis of the pavement structure. The conclusion is as follows:(1) The results show that when the stronger of the integrity between new and old roadbeds, the greater of the resilient modulus in the new subgrade, the greater of the thickness of the pavement structure, then the stress load is smaller.When the greater differential settlement after construction, the smaller the thickness of the pavement structure, the stronger intergity of the pavement structure between the old and new roads, the greater width of the broden panels, the greater the additional stress generated by the settlement of the pavement structure will be formed. When other conditions are the same, the additional stress of the pavement structure which is exactly proportional to the settlement.(2)Studies have shown that when the municipal roads are reconstructed and expanded, it is necessary to broaden the additional side cushion. With the cushion material modulus greater than 200 MPa, it is recommended the base thickness should be greater than 36 cm, appropriately adopting 38 ~ 40 cm.(3)For the first condition, when the new and old roads splices are unilaterally widened, it is recommended that the pavement thickness of the cement concrete appropriately should be 28 cm. For the second condition, when it is unilaterally widened and the rubblization on the old pavement, it is recommended that the pavement thickness of the cement concrete appropriately should be 28 cm. For the third condition, when it is bilaterally widened in symmetry, it is recommended that the pavement thickness of the cement concrete appropriately should be 20 cm, which is also the most economical solution. For the fourth condition, when it is bilaterally widened but not in symmetry, and the middle line of the road is deviated from the junction of the new and old roadbeds, driving normally the lane is in a disadvantaged position, then we consider to wipe out till the central line and splice again. For the fifth condition, when it is unilaterally widened and the old pavement are fully wiped out, it is recommended that the pavement thickness of the cement concrete appropriately should be 28 cm.(4)When the old municipal road is intact, it is recommended to adopt the first and third conditions. When we meet the fourth condition, then we can consider to wipe out till the central line and splice again. When the old municipal road is rubbled, we can implement the second and fourth conditions to deal with the problems.(5) Analysis shows that the thickness of asphalt overlay is at least 6cm, but it is recommended that the thickness should be 8 to 10 cm.