Research On The Design Scheme For Upgrading And Reconstructing Of Pavement Structure Of SongLiao Section Of DaGuang Highway

The highway from Daqing to Guangzhou is an important component of Chinese"7918"highway-net. It's the fifth longitudinal line of the nine roads linking the north and the south.It's a main highway in the northeast and in the expressway programme of Jilin province. It's also an important road crossing the westen part of the northeast of China. Its construction would give great significance to the completation of national and regional road-net, the exertion of advantages of highway-net, the strengthen of economy cooperation within and between provinces and the harmony development of society and economy in the northeast industry base.The highway from Songyuan to Shuangliao (Ji-Meng boundary) is a part of the Daqing to Guangzhou highway, which originates from Changling, Songyuan, and connects with the project from Ulatara to Changling, which ends to Shuangliao (Ji-Meng boundary) and connects with the project of Tongliao to Shuangliao of the Daqing to Guangzhou highway. This reconstruction uses half of the existing Class I roads. The original half of the highway pavement structure is also need upgrading, so as to improve the function and performance and the service level of the road.The road comprehensive investigation and evaluation include six aspects: 1.the pavement damage status, 2. the rut on road surface, 3.the pavement roughness, 4.the road sliding resistance performance, 5. pavement deflection, 6. the observation of old pavement thought core sample. According to the comprehensive evaluation result, the situation of this road is fairly good after four-year use. The PQI optimal ratio of excellence is 70.56%. The main disease is transverse cracking. Pavement structure could be upgraded by paving asphalt layers after disposing the oringinal condition.According to the traffic and transportation analysis in the engineering feasibility study report, this paper determines the total standard accumulative axial times of Songliao section of Da-Guang line by calculation. Because of the requirement of clearance under bridges, the thickness of reinforcing layer on the old road must be no more than 15cm.In order to obtain the most economical and reasonable road rehabilitation scheme, we draw up a comparable plan that makes up with three schemes: add one layer, add two layers and three layers up the old road surface (including milling and regeneration on the old pavement).Among them, the types and thicknesses of the asphalt mixture are preliminary programmed under the real design and construction situations.As for the three rehabilitation programs, this article used the HPDS software to calculate the thicknesseses of the overlayers, and also used the Bisar software to check the bottom stresses of the semi-rigid subgrade, getting the following conclusions: Plan NO.1 (add a Stone Mastic Asphalt Mixtures SMA-16 layer thicked 6cm on the old road directly) It can't be used because it couldn't satisfy the requirement of the overlay in different types.Plan No.2 (add two layers on the old road. The upper one is a Stone Mastic Asphalt Mixtures SMA-16 layer thicked 5cm, and the lower one is a asphalt mixture AC-20 layer thicked 7cm) Although it can satisfy the requirement of the overlay in different types, the bottom stresses of the semi-rigid subgrade may be beyond the allowed value when the sections between overlayer and the old road surface, the old road and the subgrade are uncontinuous, even if the lower layer is 8cm. It is not recommended.Plan No.3 (mill the older road by 4cm, and then add three layers of the asphalt mixture. The top one is a Stone Mastic Asphalt Mixtures SMA-16 layer thicked 5cm, the middle one is a asphalt mixture AC-20 layer thicked 7cm, and the bottom one is a layer of regenerate asphalt mixture thicked 7cm) It can satisfy the requirement of the overlay in different types, and the bottom stresses of the semi-rigid subgrade are bellow the allowed value when the sections between overlayer and the old road surface, the old road surface and the subgrade are uncontinuous.Finally, this article analysised the overall cost based on the construction cost and the maintenance cost. Through the life-cycle cost analysis, we can know that the cost of Plan No.3 is lower than the other two in the given years, so the Plan No.3 is an ideal paving scheme. It is recommended.