1. 1 project management reason: the asphalt pavement is uneven, and the project management level has a great influence on the smoothness of asphalt pavement. The quality of construction personnel (including construction managers, construction teams and workers), project quality management system and quality assurance system, the ability and effect of executing procedures, project management and construction experience will have a great impact on the smoothness of asphalt pavement.
1.2 subgrade quality reason: the asphalt pavement is uneven, and the subgrade is the foundation of the road pavement. The uneven settlement of subgrade will inevitably lead to uneven pavement. The reasons for uneven settlement of subgrade generally include: ① poor control of subgrade backfill materials and uneven pavement; (2) The junction of half-dug and half-filled subgrade is not handled properly, and the compactness of subgrade is not enough; (3) Improper or inadequate treatment of special subgrade sections, imperfect subgrade protection and drainage, subgrade bearing subgrade deformation caused by insufficient subgrade weight or vehicle load, etc. , resulting in uneven settlement of subgrade.
1.3 Backfilling around the inspection well: In the urban roads that have passed, due to the improper construction of the inspection well foundation, the manhole cover or the surrounding area often sinks to varying degrees. The main reason is that the backfill around the inspection well is not dense, which leads to the subsidence around the inspection well, or because of the leakage of the inspection well, the backfill soil around the inspection well is washed into the well, forming a cavity around the inspection well or softening the backfill around the well, and sinking under the repeated action of dynamic load (vehicle), resulting in uneven asphalt concrete pavement. This phenomenon often occurs in urban road reconstruction. The perimeter of the previously built inspection well has been partially hollowed out. At the same time, because the manhole foundation is not processed properly or the foundation strength does not meet the design and specification requirements, the manhole foundation strength is destroyed, which fails to meet the design requirements after completion. Under the repeated action of vehicles, the manhole as a whole sinks, or because the mortar curing period under the well ring is insufficient and not full, and the mortar is too thick, the manhole and manhole cover sink under the repeated action of vehicles.
1.4 The bump at the bridge head at both ends of the bridge and culvert seriously affects the overall smoothness of the road surface: the subgrade disease at both ends of the bridge and culvert is one of the most common road diseases in urban roads. The main manifestations are as follows: (1) Backfilling of bridge and culvert abutment is due to the narrow working surface of compaction machinery, and the compaction is not in place, resulting in compression and settlement of subgrade after opening to traffic; (2) There is a big difference between the stiffness of abutment back filler and abutment body, resulting in uneven settlement.
1.5 unevenness of base course causes unevenness of pavement: in the process of pavement base course construction, slight unevenness of base course can be compensated in surface course construction, but poor smoothness of base course will inevitably affect the smoothness of surface course. Because there are too many bumps at the grass-roots level, the two tracks of the paver will run on the uneven road surface, so that waves will appear at both ends of the screed of the paver. In addition, because the base is uneven, even if the surface is paved flat, the surface will be uneven after rolling because of the different thickness of virtual paving.
1.6 Influence of asphalt concrete quality on the smoothness of asphalt pavement: The quality of asphalt concrete not only affects the structural quality of asphalt pavement, but also affects the smoothness of pavement. The quality of asphalt concrete depends on the quality of main materials, the mix design of asphalt mixture and the mixing of asphalt mixture.
1-7 influence of paving machinery and paving construction technology on smoothness: asphalt paver is the main mechanical equipment for asphalt pavement surface construction, and its performance and operation have great influence on paving smoothness. Unstable structural parameters of paver, skid of walking device, uneven paving speed of paver, violent start and emergency braking of machinery, and fast and slow speed of feed system will all cause uneven surface and waves. At the same time, the construction technology of asphalt pavement has great influence on the smoothness of pavement. The common defects of asphalt concrete pavement joints are: sinking or bulging at the joints, cracks or even looseness at the joints due to insufficient density and bonding strength, resulting in uneven pavement. This phenomenon appears on urban roads to varying degrees.
1.8 Influence of rolling machinery, equipment and technology on smoothness of asphalt pavement: Rolling after paving asphalt pavement has an important influence on smoothness, including selection of rolling equipment and control of rolling technology. The selection and combination of rolling machinery, rolling temperature control, speed control, rolling route, rolling sequence and rolling times are all related to pavement smoothness.
2, treatment measures:
2. 1 project management: for asphalt concrete pavement, it is necessary to have construction experience and excellent management level of similar projects, including good personnel quality, strict project quality management system and quality assurance system, and the ability and effect of implementing procedures. Construction management personnel mainly need to prepare special plans for key parts and parts prone to problems. For the construction team and workers, it is necessary to effectively disclose and supervise the construction process. Construction personnel mainly carry out specific construction operation and process inspection according to the contents disclosed by technical personnel to ensure the reduction and effective prevention and control of the above common phenomena.
2.2 Countermeasures for uneven settlement of subgrade: The construction quality of subgrade is the key to road engineering, and it is also the test of whether subgrade and pavement engineering can withstand time, vehicle running load, rainy season and winter. To do a good job in subgrade engineering, subgrade filling must be carried out in accordance with the requirements of specifications and technical standards.
2.3 Backfilling around the inspection well and foundation treatment of the inspection well: In the process of subgrade backfilling, the periphery of the inspection well should be backfilled together with the subgrade, and the field roller should be rolled to the periphery of the inspection well as far as possible. After backfilling to a certain height, all the soil around the inspection well that has not been rolled in place will be removed by reverse excavation and replaced with sand or other high-quality fillers that are convenient for construction.
2.4 Precautionary measures for vehicle bumping at both ends of bridges and culverts: design a transition section at the bridge head, that is, lay a transition pavement or set a strap within a certain length range to avoid vehicle bumping at both ends of bridges and culverts.
2.5 Precautions for pavement base construction: During the construction of asphalt pavement base, the smoothness of each base should be well controlled, and the higher the requirements, the higher the smoothness of the pavement can be guaranteed. (1) Subbase and base construction shall be carried out in strict accordance with Code for Construction and Acceptance of Urban Road Engineering (CJJ1-2008) to ensure that the elevation, cross slope, strength and flatness meet the design requirements. When the paver is used for base construction, the transverse diagonal bars on both sides of the paver can be properly adjusted to make the screed in a state of low middle and two ends tilted. Before the surface layer is laid, carefully clean the base surface to ensure that the base surface is clean and tidy, and there are no loose floating materials and impurities. (2) Strengthen grass-roots maintenance. After the base construction is completed, cover it with geotextile, spray asphalt emulsion for protection, or spray water for maintenance to keep it moist, and vehicles are prohibited from going up during maintenance.
2.6 Control the influence of asphalt concrete quality on smoothness: (1) Strictly control the raw materials of asphalt concrete, which should meet the relevant specifications and design requirements, especially the coarse aggregate should be clean and the indicators such as strength and wear resistance should meet the requirements, and the fine aggregate, asphalt materials and fillers should also meet the corresponding technical requirements. At the same time, the mixture ratio should also meet the above specifications and design requirements. (2) Strictly control the temperature. In the process of mixing, if the temperature is too high, it may cause asphalt aging and the paving quality cannot be guaranteed. However, when the temperature of the mixture is not enough, or when the equipment fails, the temperature may be uneven. Therefore, the mixing temperature and ex-factory temperature of asphalt mixture should be strictly controlled. (3) Strictly control the mixture ratio. With high asphalt content, the pavement is easy to be flooded, while with low asphalt content, white aggregate is easy to appear, which makes the adhesion between aggregates poor, the pavement easy to loosen, and even potholes appear, which affects the driving safety and comfort.
2.7 Control and paving construction technology of asphalt paver: (1) Main control of asphalt paver: ① Carefully check and test the automatic leveling device and sensor of paver; (2) Before paving, the screed of paver should be heated and adjusted. The temperature of screed must meet the specified requirements, and the straightness of screed should not appear positive arch and reverse arch; (3) Choose the appropriate frequency and do a good job of trial paving. At the same time, during the paving process, you should always check the vibrator, tamping belt, etc. (2) Construction process control of asphalt pavement paving: ① Paving progress control of paver, which should be paved continuously at a constant speed without stopping, and it is forbidden to be fast or slow; (2) Paver operation control measures, select skilled paver operators and conduct pre-job training. When the pause time exceeds 30 minutes or the temperature of the mixture is lower than 100%, the joint should be re-jointed as the cold joint is treated.
2.8 Asphalt pavement rolling and joint quality control: The rolling of asphalt concrete pavement is usually divided into three stages, namely initial rolling, secondary rolling and final rolling. Rolling mode, method, speed and temperature control shall conform to the current construction acceptance specifications and design requirements. The rolling operation in each stage is always carried out when the mixture is in a stable state. Rolling operation should be from bottom to top, with static pressure first and then vibration rolling. When rolling, the driving wheel is in front and the driven wheel is behind. When reversing, you should drive forward along the crushed wheel tracks.