A road roller, also known as a soil roller, is a type of road construction equipment.
Road rollers belong to the category of road equipment in engineering machinery. They are widely used in filling and compaction operations of large-scale engineering projects such as high-grade highways, railways, airport runways, dams, and stadiums. They can roll sandy, semi-viscous and cohesive soils, roadbed stabilized soils, and asphalt concrete pavement layers. The roller uses the gravity of the machine itself and is suitable for various compaction operations, causing the rolled layer to be permanently deformed and compacted. Rollers are divided into two types: steel wheel type and tire type.
1. Classification and scope of use of rollers
According to the working principle of the roller, rollers can be divided into three categories: static rollers, vibrating rollers, and compaction machinery.
- Static rollers
Static rollers are suitable for various compaction operations, causing the rolled layer to be deformed and compacted. Including various types of light-wheel rollers, tire rollers (referred to as tire rollers), sheep-foot rollers (referred to as sheep-foot rollers), convex rollers (referred to as convex rollers) and various drag rollers.
- Vibratory rollers
The working mass of single-wheel vibratory rollers is mostly 10-25t or 30-50t. With the development of highways, large-tonnage vibratory rollers are widely used.
The working mass of double-wheel vibratory rollers mainly includes light (2-4t), medium (5-8t) and heavy (10-14t).
1.1 Scope of application of rollers
- Light-wheel rollers
The unit line pressure of light-wheel rollers is small and the compaction depth is shallow. Light and medium-sized light-wheel rollers are suitable for compacting general soil roadbeds, gravel, and crushed stone bases. Heavy and extra-heavy-duty light-wheel rollers can compact block-filled roadbeds and crushed stone structure layers.
- Sheep-foot roller (referred to as "sheep-foot roller")
Sheep-foot roller has a large unit pressure (including the squeezing force of the sheep's foot), a large and uniform compaction depth, and can crush soil blocks, so it has a good compaction effect and high productivity, and is widely used for layered rolling of cohesive soil. Because of the above advantages, the sheep-foot roller can also adjust the unit pressure of the sheep's foot by increasing or decreasing the counterweight. It is often used to roll impermeable cohesive soil in earth dam construction. The sheep-foot roller has a poor compaction effect on non-cohesive soil and high-water content clay, so it is not suitable for use.
- Tire roller
Tire roller has good mobility and is easy to transfer. When compacting, the soil and the tire deform at the same time, the full pressure acts for a long time, the contact area is large, and it has a kneading effect, and the compaction effect is good. Tire roller is suitable for compacting cohesive and non-cohesive soils, such as clay, sandy clay, sandy soil, gravel, etc.
- Vibratory roller
The unit line pressure of the vibratory roller is large, and the vibration force has a deep impact, so the compaction depth is large, and the number of rolling times is reduced accordingly. There are many types of vibratory rollers and they are widely used. The smooth wheel vibratory roller is suitable for compacting non-cohesive soil (sand, gravel), crushed stone, and block stone. This type of roller can also be used as a static compaction machine for leveling operations after disconnecting the vibrator.
Sheep foot or bump vibratory rollers can compact non-cohesive soils, as well as cohesive soils with low water content, fine-grained gravel, and crushed stone soil.
The biggest disadvantage of the vibratory roller is that its high-frequency vibration can easily cause excessive fatigue to the operator, affecting its promotion and use. At present, vibratory rollers have adopted a variety of new structures such as tire vibration reduction, articulated frame, and hydrostatic transmission. The vibration reduction problem has been basically solved. In the construction of earth-rock dams at home and abroad, 5-15t vibratory rollers are mostly used for compaction.
Sheep-foot or convex-block vibratory rollers can compact non-clay soils as well as viscous and fine-grained gravel mixtures with low water content. The applicable scope of vibratory rollers is shown in Table 4.4.1.
- Compacting machinery
Vibratory tamping is suitable for compacting non-viscous sandy clay, gravel, and crushed stone; while impact tamping is suitable for compacting clay, sandy clay, and gray soil.
A light-wheel roller is equipped with one operator, while a towed sheep-foot roller, towed vibratory roller, and vibratory roller are equipped with two operators.
2. What performance index parameters should be considered when purchasing a roller
Common performance index parameters of rollers include vibration frequency and amplitude, linear load, weight and thrust, travel speed, and climbing ability. Their reasonable adjustment and control will have a direct impact on construction efficiency and quality.
- Vibration frequency and amplitude
Vibration frequency refers to the number of vibrations per minute, and amplitude refers to the maximum vibration amplitude of the vibrating wheel or vibrating steel wheel. Vibration frequency and amplitude are one of the main performance indicators of the roller. Their functions are to increase the compaction force, enhance the density and stability of the soil, and improve the bearing capacity and durability of the road surface. Generally, the vibration frequency and amplitude are inversely proportional, that is, the higher the vibration frequency, the smaller the amplitude; the larger the amplitude, the smaller the vibration frequency. In order to achieve better compaction effect, it is necessary to adjust the vibration frequency and amplitude according to different road sections and different soil conditions.
- Linear load
Linear load refers to the load per unit length of the roller pulley or tire. It determines the compaction capacity and compaction depth of the roller, and is closely related to the vibration frequency and amplitude. Generally, the larger the linear load, the stronger the compaction capacity, but the degree of damage to the road surface should also be considered. In addition, the distribution of linear load should be considered and controlled during construction to avoid excessive concentration causing damage to the road surface and poor compaction effect.
- Weight and thrust
Weight and thrust are also one of the main performance indicators of the roller. They directly affect the size of the compaction force and the level of construction efficiency. Generally speaking, the greater the weight, the greater the thrust, the greater the compaction capacity and compaction depth of the road surface; conversely, the smaller the weight, the smaller the thrust, and the lower the efficiency. When choosing a roller, the appropriate weight and thrust should be selected according to the actual work needs and site conditions.
- Travel speed and climbing ability
Traveling speed and climbing ability are two other important performance indicators. Traveling speed has a great impact on construction efficiency. The appropriate traveling speed should be selected according to the construction site and needs to avoid being too fast or too slow. Climbing ability is very important for situations where the road slope is large or climbing construction is required. When choosing a roller, pay attention to whether its climbing ability meets the needs.
3. Advantages of rollers
- High efficiency
Road rollers can achieve a strong effect when reinforcing the ground, with a faster working speed and higher reinforcement quality. In the foundation construction of roads, bridges, sites and other projects, the use of rollers has a significant reinforcement effect than other reinforcement equipment.
- Wide construction area
Road roller is a mobile mechanical equipment that can be used in different work sites and terrain conditions, and can adapt to various road construction requirements.
- Simple operation
Road roller operation is relatively simple compared to other construction machines. Only basic training is required to operate it proficiently.
- Energy saving
The design of the road roller makes it have high energy utilization efficiency, which can reduce fuel and engine operating load, thereby reducing energy consumption and reducing pollution emissions.
4. Operating procedures of road roller
- During operation, the road roller should start before vibration, and the internal combustion engine should be at medium speed first, and then modulated to high speed.
- Stop the machine first when changing speed and reversing, and reduce the speed of the internal combustion engine when changing speed.
- It is strictly forbidden for the road roller to vibrate on solid ground.
- When rolling soft roadbed, it should be rolled 1~2 times without vibration first, and then vibrated and rolled.
- The vibration frequency should be kept consistent during rolling. For adjustable vibratory rollers, the vibration frequency should be adjusted before operation, and the vibration frequency should not be adjusted without vibration.
- The adjustment of the reversing clutch, the shock clutch and the brake should be carried out after the main clutch is disengaged.
- When going up or downhill, the fast gear cannot be used. When making sharp turns, including when the articulated vibratory roller is rolling in a small turn, it is strictly forbidden to use the fast gear.
- The roller must not engage the vibration when driving at high speed.
- When stopping, the vibration should be stopped first, then the reversing mechanism should be placed in the middle position, the transmission should be placed in neutral, and finally the hand brake lever should be pulled up, and the internal combustion engine should be turned off after idling for several minutes.
5. Cleaning, storage and transportation of the roller
- Cleaning of the roller
After each operation, the dirt and dust must be rinsed off. At this time, special attention should be paid to the cleaning of the diesel engine, generator, starter motor, injection pump, injector, hydraulic pump, etc. Wipe these places with a dry and soft rag.
If the roller is parked for a long time, the water in the engine water tank must be drained. Carefully clean the dirt and dust on the machine, wipe the outer surface of each component and all lubricants with kerosene, and write down the oil immediately.
- Storage of rollers
Road rollers should be stored in dry warehouses, and it is strictly forbidden to store irrelevant items and gasoline. When parking in the open air, the ground should be kept dry. It must be covered with a rainproof cloth.
- transportation of rollers
When transporting rollers over short distances, high-speed rollers can be selected according to road conditions. When transporting rollers over long distances, roadside machines are suitable for flatbed trailer transportation. During the suspension and transportation process, the safety locking device on the fuselage is used to lock the frame to prevent the fuselage from rotating relative to each other. At the same time, the flatbed is prepared.
