Cause analysis: asphalt pavement diseases are mainly manifested in longitudinal and transverse cracks, and rainwater permeates down along the cracks to form pumping slurry at the crack edge, as well as a small number of network cracks, local looseness, pits and grooves, flooding and so on. The development of asphalt pavement diseases in the whole line has certain stages, mostly located in the back backfill of bridges and culverts and high embankment. In the winter of 1~ before opening to traffic, some small short cracks appeared, and most of them healed with the increase of temperature. After several storms, rain and snow, the original cracks in asphalt pavement cracked again, and many short cracks appeared in the driveway. After being opened to traffic for 3 years, the service level of asphalt pavement is greatly affected by the development of long and short joints with joint width greater than 5mm, joint gnawing edge and structural damage of joint edge. Most of the diseases of asphalt pavement are transverse cracks, and only a few are longitudinal cracks, reticular cracks, cracks or subsidence, pits and grooves, and pumping slurry, which shows that the overall strength of each layer of pavement is no problem. Through a large number of investigations, it is considered that the causes of pavement diseases are as follows: 1. Shrinkage cracks of cement stabilized macadam. Cement stabilized macadam is a semi-rigid material. With the passage of time, dry shrinkage and temperature shrinkage will occur, and the shrinkage cracks of semi-rigid base will inevitably be reflected on the surface. The strength-energy pavement is a kind of flexible material, which has certain anti-deformation ability, so there are fewer cracks in the road section with good subgrade compaction. Second, traffic load and rain accelerate the development of cracks. Cement stabilized macadam will produce fine cracks for various reasons during construction and operation. According to the theory of fracture mechanics, the energy stored in semi-rigid base is provided by traffic load, and the energy is consumed through the unstable expansion of cracks. This process is repeated repeatedly, so that the independent cracks expand into several macro cracks, until the small cracks in the New Year process, and finally become through cracks. This is why there are more cracks in the lane than in the overtaking lane. Because there are pores in the asphalt surface, water seeps into the pavement after rain or snow melting, but after several days of rainy and sunny weather, there is still a lot of water on the pavement surface due to the water resistance of soil shoulders. A large amount of water keeps gathering at the crack and permeates downward along the crack. Because of the high strength and compactness of the base, it is difficult to discharge water, which is easy to cause changes in the interface conditions and stress state of the pavement. Under the action of traffic load, the cracks are boiled, and the cement stabilized macadam falls off and loosens due to water, and the bearing capacity of pavement structure is insufficient, resulting in edge gnawing, which may develop into network cracks, pits and subsidence. The overload phenomenon is serious, which aggravates the spread of pavement diseases. The drainage of asphalt pavement is the first, and poor drainage will inevitably cause great trouble to the pavement. Overload is the "first killer" of expressway, and water is the "culprit" of pavement damage. 3. The longitudinal cracks caused by the approach of the bridge, starting from the abutment, all appear on the embankment with a height of more than 6m, and there is no obvious dislocation on the surface. The analysis shows that it is caused by a small amount of settlement or outward sliding of high embankment, and there are fewer longitudinal cracks in low embankment. Four, there are some technical and procedural problems in the construction. The uneven segregation of pavement asphalt is serious, which is easy to cause local water seepage and cause pavement diseases. Insufficient compaction during construction is also an important reason. Due to the one-sided pursuit of pavement smoothness, it is impossible to carry out technical compaction at high temperature and dare not use tire rollers, which makes the pavement surface look smooth and rot quickly after opening to traffic. It is suggested that compaction management should focus on compaction process management. In construction, construction pollution is also an important cause of early pavement damage. During the construction process, the bottom layer of the pavement was stolen, which led to the failure to form an organic whole between layers, and the "plywood" became a "plywood". Under normal circumstances, bridge deck pavement and asphalt pavement should be constructed continuously, but some bridge deck projects are often cross-quarter, and the pollution of bridge deck pavement and asphalt pavement will inevitably cause pavement diseases. To sum up, the occurrence of asphalt pavement diseases in Jining section of Beijing-Fuzhou Expressway is the result of many factors. Maintenance design of early diseases of asphalt pavement: 1, maintenance design of early diseases of asphalt pavement and use of new maintenance materials. For thin joints with a joint width of less than 5mm, diluted asphalt or new pouring material (sealant) should be poured into the joint for more than 3cm. For wide cracks, it is impossible to judge whether there is structural damage. In the detailed field investigation, the superficial phenomenon is compared, and representative cracks are selected for damage inspection. If it is determined that there is no structural damage to the wide joint and the edge is not gnawed, the sundries in the joint will be blown out by a powerful blower to assist manual cleaning, and the joint will be filled with diluted asphalt or new pouring material to make it more than 5cm. If the joint is wide, cut off the crack about 10cm, fill it with fresh asphalt mixture, and manually compact it. If the joint width has been chewed but not extended, the upper layer with a thickness of 4cm and a width of 50cm shall be removed on both sides of the crack, the emulsified asphalt shall be painted on the bottom layer as the bonding layer oil, and the double-sided adhesive tape of polymer shall be pasted on the facade wall to ensure the bonding of new and good asphalt binder and play a waterproof role, and finally the asphalt mixture on the upper layer shall be paved. If it is judged as structural failure, such as network cracking and subsidence, the upper layer is removed with a width of about 1.8m, and the cracks are cut off with a width of about 10cm. Emulsified asphalt and polymer will be painted on the bottom surface and bonded side walls, and a new waterproof and anti-crack material-polymer anti-crack adhesive will be laid abroad. Polymer anti-crack stickers can effectively slow down or prevent the occurrence of reflective cracks in newly-built overlay, protect the original pavement structure and prolong the service life of the road on the premise of reducing the road maintenance cost. On this basis, the upper asphalt mixture is paved and compacted manually. If the middle and lower floors are damaged, they should also be removed and filled with fresh asphalt concrete; If the cement stabilized macadam is damaged, it should be moved to a hard place with complete structure, coated with concrete adhesive and filled with 30 # expansive concrete, and the middle and lower layers should be filled with fresh asphalt concrete. 2, asphalt pavement early disease maintenance construction and matters needing attention. In the early maintenance and construction of asphalt pavement, it takes a long time to repair the old pavement by spraying emulsified asphalt adhesive layer oil and laying glass fiber mesh, and finally paving a new asphalt pavement. Therefore, the corresponding organization work should be done well in the construction. (1) Construction paragraph division and traffic organization. Construction warning signs, speed limit signs, guide signs and necessary safety protection measures must be set on the construction site according to international GB5768- 1999 or Technical Specification for Highway Maintenance (JTJ-96) of the Ministry of Communications. (two) the implementation of the construction unit and personnel, mechanical organization. Select qualified construction units through formal bidding procedures. The construction unit should organize enough manpower, machines and tools and all kinds of meta-materials, and shorten the construction time as much as possible in each section. The construction unit shall organize road personnel, do a good job in traffic organization and traffic guidance on the construction site, and designate qualified supervision units to carry out supervision. (three) milling waste, should choose a suitable place to pile up outside the scope of highway land. (4) Arrange the time reasonably, and try to arrange the spring and autumn seasons to avoid the rainy season and the golden season of traffic flow. Follow-up investigation of early maintenance effect: since it was opened to traffic at the end of 2000, the fine joints with joints less than 5mm have been poured, and the cracks (including net cracks, local potholes, subsidence, slurry pumping, rutting, etc.) have been completed. The damaged joints with the structures along the line have been repaired in time, the early diseases have been effectively controlled, and the quality of pavement maintenance has been good. The early maintenance of expressway asphalt pavement is a very important work, which should be highly valued by expressway management departments. The early damage of pavement has also been treated, and now preventive maintenance and comprehensive maintenance centered on pavement are advocated. In order to do preventive maintenance well and avoid early pavement damage, we must increase research, dare to practice and be good at practice, and form preventive maintenance theory and norms as soon as possible. Effective early maintenance can not only improve the early service level of asphalt pavement, but also greatly prolong its effective life.

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