What is the reason for uneven compaction of steel wheel rollers?

1. Operational factors
1. Uneven driving speed: During the compaction process, if the driving speed of the steel wheel roller is too fast, the contact time between the steel wheel and the ground will be too short, and the pressure will not be fully transmitted to the road material in time, resulting in uneven compaction. On the contrary, if the driving speed is too slow, the steel wheel will stay in the same position for too long, resulting in excessive compaction of that part and insufficient compaction of other parts.
2. Improper steering operation: During the steering process, the inner and outer driving trajectories of the steel wheel roller are different, the outer steel wheel travels a longer distance, and the inner steel wheel travels a closer distance. If the steering operation is too hasty or unstable, the driving speed difference between the inner and outer steel wheels will be large, resulting in uneven compaction. In addition, the change in the angle of the steel wheel during steering will also affect the distribution of pressure. Too large or too small an angle will lead to uneven compaction.
3. Inconsistent compaction times: When performing large-area compaction operations, due to the operator's negligence or improper operation, some areas may be compacted more or less than other areas. The difference in the number of compaction passes will directly affect the compaction degree of the pavement material, resulting in uneven compaction.
2. Equipment factors
1. Uneven wear of the steel wheel: The steel wheel of the steel wheel roller will wear unevenly due to friction and wear with the ground during long-term use. For example, the edge of the steel wheel may wear faster, while the middle part wears relatively slowly. Unevenly worn steel wheels will cause uneven pressure distribution during compaction, thus affecting the compaction effect.
2. Vibration system failure: The vibration system of the steel wheel roller is an important device to improve the compaction effect. If the vibration system fails, such as unstable vibration frequency, uneven amplitude, etc., the steel wheel will not be able to generate uniform vibration energy during the compaction process, thereby affecting the compaction uniformity of the pavement material.
3. Frame deformation: The frame is an important supporting structure of the steel wheel roller. If the frame is deformed, the installation position and angle of the steel wheel will change, thereby affecting the contact state and pressure distribution between the steel wheel and the ground. Frame deformation may be caused by fatigue damage, collision accidents or improper storage methods during long-term use.
4. Inconsistent tire pressure: For some steel wheel rollers equipped with tires, if the tire pressure is inconsistent, the roller will tilt or bump during driving, thus affecting the contact pressure between the steel wheel and the ground and the compaction uniformity. In addition, too low tire pressure will increase the rolling resistance of the tire and reduce the working efficiency of the roller.
III. Material factors
1. Uneven pavement material: If the pavement material itself is uneven, such as inconsistent particle size and different water content, it is difficult to achieve uniform compaction even if the operation and equipment status of the steel wheel roller are normal. For example, when paving asphalt mixture, if the aggregate gradation in the mixture is unreasonable, and the large and small aggregates are unevenly distributed, the steel wheel will not be able to apply uniform pressure to all particles during the compaction process.
2. Uneven material stratification: When constructing a multi-layer pavement structure, if the flatness between the layers of material does not meet the requirements, there is a large height difference or unevenness, the steel wheel roller will be subject to uneven resistance during the compaction process, thus affecting the compaction uniformity. For example, if the surface of the base layer is uneven, the thickness of the surface layer material will be inconsistent during the compaction process, affecting the flatness and compaction quality of the road surface.
4. Environmental factors
1. Temperature changes: The ambient temperature has a great influence on the physical properties of the road surface material. In a high temperature environment, the viscosity of the road surface material decreases, and it is easy to produce flow deformation. The steel wheel roller needs to adjust the compaction parameters appropriately during the compaction process, otherwise it may cause uneven compaction. In a low temperature environment, the brittleness of the road surface material increases, and the compaction energy of the steel wheel roller is difficult to effectively transfer to the inside of the material, which will also affect the compaction effect.
2. Humidity changes: The water content of the road surface material also has an important influence on the compaction effect. If the road surface material is too dry, the friction between the particles is large, and it is difficult for the steel wheel roller to compact it; if the water content of the road surface material is too high, the viscosity of the material will increase, and it is easy to stick to the wheel, affecting the compaction uniformity. In addition, changes in humidity will also cause changes in the volume of the road surface material, further affecting the compaction effect.