Application Study On LSPM Flexible Road Base Of Ji-Liao Express Highway Heavy Maintenance

With the rapid development of traffic transport, the heavy vehicles, round pressure increasing and vehicle traffic drainage, lacking rutting capacity and the increase of early damage appeared on Asphalt Pavement. Pavement Performance decays accelerating, greatly shortened the working life. To meet the increasing traffic, increasing proportion of heavy trucks, in the early "July 5" - the "Eighth Five-Year Plan" period, has been made remarkable achievements used by research in semi-rigid base course asphalt pavement research and Application.At present, the widely used semi-rigid base course structure is lime-fly ash stabilized aggregate and cement-stabilized gravel. These two base's primary advantages is prominent high strength and modulus, good overall stability and durability and easy construction, strength and modulus increases gradually as age so many series of fine road performance, thus to promote large-scale applications, which has played a tremendous role for highway construction and economic development.However, as long-term use and research, it was found that the widespread used semi-rigid asphalt pavement, Although resolves the shortage of strength, because of a large volume contraction (temperature and dry shrinkage), water stability margins (lime-fly ash stabilized aggregate base)of semi-rigid material cause reflect cracks on the road surface and poor drainage problems. Pavement cracking, loose and so on damage phenomenon is common, which seriously impact on the service road, caused considerable economic losses and adverse social impacts.How to resolve the semi-rigid pavement reflection cracks and poor drainage is one of the issues to be resolved. This paper uses LSPM big grain asphalt mixture as asphalt base, and through the rational design of the pavement structure, thus resolve these two issues.The first chapter introduces the thesis research purposes and research situation at home and abroad. Aimed at Jiliao highway traffic is heavy, traffic grows fast; large proportion of trucks, more overloaded vehicles, big axis and so on characteristics in traffic composition, at the same time, the thickness of pavement design is too small, the overall strength is lack; pavement structure is irrational; Pavement structure without installing drainage layer and causing rutting on the surface and water damage destruction. By adopting LSPM flexible base and and rationally design pavement structure to solve these problems.The second chapter deals with the study on LSPM Asphalt Mix Design and Performance. Firstly expound strength and distribution theory of asphalt mixture; secondly, do trial study on asphalt mixture of raw materials, and based on five different class grading, through asphalt mixture unconfined compressive strength and modulus would determine a reasonable grading. Then, use compaction and vibrating, study on the asphalt mixture unconfined compressive strength,modulus trabecular bending test of this grading. Under the vibration effect, the mixture easily formed squeezed skeleton structure, thus the mechanical properties correspondingly increased. In particular, the strength and performance of resilient modulus, the compressive strength after vibrating increased 15.8%, Modulus increased 47.0%; the bending strain under compaction molding increased 18.2%, stiffness modulus decreased by 9%, which explain that asphalt mixture which has vibrated is more flexible.The third chapter describes the design optimization program of Jiliao highway. And receive the following conclusions: (1)The total thickness of pavement structure is big, the total thickness of pavement structure reaches 92 cm, Asphalt Pavement total thickness is 23cm, which meet the design principles of long life (USA Milwaukee governor the total thickness of asphalt layer on the long life test sections is about 23cm), it is a very useful exploration.(2)The structure combination is more rational, LSPM can more effectively prevent reflective surface cracks to spread, and it is more in favor of drainage, more responsive to the needs of heavy traffic.(3)Consider the drainage and waterproof design, reduce stagnant water pavement layer which can effectively prevent water damage.(4)The semi-rigid base course implements intensity grading, there is more stringent requirements on the grading, grading range is relatively small, mainly depending on squeezing to gain the aggregate strength, and not rely on the combined strength of the materials themselves. This is a change and trial of design concept on semi-rigid base course material.The fourth chapter discusses the paving and test of Jiliao highway. The construction process of Jiliao highway should be strict requirements, including the mixture of transport, paving and rolling, quality control, segregation control. In particular, the mixed press is very important, concrete steps are:(1)Use two wheels vibratory roller, first press is ahead press and retreat vibration; the second times are ahead retreat and vibration pressure. The speed of compaction is 1.5-2km / h, in order to prevent excessive vibration and then break coarse aggregate. We should adopt high-frequency and low amplitude compaction , and the adjacent superposition pulley trace is about 20 cm. Sprinkler installations intervally sprinkle, as long as assuring nonstick round. After vibration the tire roller press 1 -2 times again and then that can drive light. The speed of rush-7 -11 round roller can be controlled at 3-4km/h.(2)Rubber tire roller closely follow the paver rolling track, in order to avoid serious sticky first round of a small amount of water onto it. wait until the tire temperature rises then do not water. After the rubber tire roller compacted it the first time, it makes the mixture closely skeleton structure, and stabilize the mixture. Since then use vibratory roller to compact twice with same process as the first and then tire pressure again, finally drive.After the completion of the project, then to do the test, test results showed that adopted LSPM as base, it has excellent flatness of the lane and improves comfort, Meanwhile the excellent deflection value increases the overall strength of the road.Chapter V is the conclusions and further study scenario, summary the research work in the thesis completed the process, carry out the content and direction which will continue to conduct studies on in the work.