What Are The Operating Methods Of The Roller?
In highway construction, the rolling process is the process that requires a lot of work and requires the most quality and technical indicators, especially for the construction of asphalt pavements. The construction of asphalt pavement mainly includes three aspects: mixing, paving and rolling. And compaction is an important part, it has an important influence on various technical indicators, such as flatness, compactness and so on. In order to achieve good quality indicators in the compaction process, it is necessary to have a more comprehensive understanding of the selection of rollers and the performance of various types of rollers. During the construction of highway asphalt pavement, we configured the vibratory roller as the main compaction machine through demonstration and reference practice and played an important role in the high-speed and high-quality road paving.
The following is an analysis of the various data and performance required by the vibratory roller in highway construction.
1. The role of dual-drive dual-vibration
1.1 The force of the double-drive driving wheel on the pressed material is H′=H and R′=R. The vertical force R′ compacts the material, while the horizontal force H′ makes the material move in the opposite direction of the roller. This movement will be resisted by the compacted material behind the driving wheel, so that the moving material particles will fall in the high-pressure area close to the vertical line of the roller and be compressed, so a wave-shaped surface will not be formed in front of the driving wheel and will be compacted. The surface of the material will be fairly flat.
Because the roller adopts a two-wheel drive structure, it has excellent performance during compaction and does not produce waves, thereby ensuring the flatness of the compacted road surface. Therefore, this full-drive roller can also be called a non-corrugated roller. And this is a rigid index that the expressway must achieve.
1.2 Double vibration
Vibration can drastically reduce the internal friction of the material to be pressed, and the shear strength decreases, so the compressive resistance becomes very small, and it is very easy to remove the gas and liquid in the material to be pressed, so that they can be compacted by mutual embedding. Due to the dual-wheel vibration function, the compaction efficiency can be greatly improved during the compaction process. For the asphalt pavement, it is more conducive to the formation of the pavement and the guarantee of the construction quality.
2 Selection of amplitude and frequency
The rolling action of the road roller is mainly determined by the linear pressure of the roller, and the selection of different linear pressures depends on the strength of the stone used in the paving layer and the bearing capacity that should be achieved after rolling. Because the roller has a dual-frequency 8 amplitude, it greatly expands its scope of use, and it can have multiple working methods during work, that is, multiple line pressures are provided. The conversion of the working mode of the road roller is quite simple and fast. It can be selected reasonably according to the nature of the material, the compaction thickness and some other indicators, so it has a wide range of applications.
It can be seen that the maximum range of vibration frequency and amplitude on the compaction effect is between 25 and 50. If the amplitude is increased at the same frequency, the compaction effect and depth of influence will be significantly improved, and the roller has 8 amplitude adjustments. This "improvement" will be tangibly reflected. For the compaction of asphalt materials, the best amplitude is 0.4～0.8mm, and the adaptation frequency is 33～50Hz.
According to the actual asphalt construction thickness and material conditions, hot asphalt mixture, base course and subbase course, the amplitude adjustment value is recommended. In the construction practice, we have realized that the vibratory roller should use high frequency and small amplitude when compacting the surface layer; when compacting the base layer, use low frequency and large amplitude.
In addition, it should be noted that during the vibration process, the larger mass of the pellets will get a greater inertial force and will move down from the neighboring pellets first. Therefore, due to the difference of the size of the pellets during the compaction process, if it is a long time Vibration will cause delamination, so the vibration should end when the pores between large particles are filled with small particles with maximum compactness. Therefore, based on experience, it is recommended that the vibration time of asphalt mixture be 1~1.5min, and that of clay is 1.5min.
4 Compaction speed roller adopts 0～14.8km/h continuously variable speed, which is very suitable for compaction of various paving layers. The following compaction speeds are now recommended: soil 3～6km/h, asphalt 1.5～4km/h. In addition, the perfect combination of the wide spokes and vibration of the roller not only accelerates the compaction speed and reduces the number of compaction passes, but also greatly reduces and lightens the wheel tracks.
In addition, the roller not only has the function of a static roller, but also can use the automatic function to control the starting point by speed. Its advanced instrument monitoring system, full hydraulic transmission, and flexibility of operation provide reliable use. The guarantee of road construction has played an important role in highway construction.