I. Compaction Principle of Tire Rollers

Tire rollers (also known as rubber-tyred rollers) compact materials by combining static pressure generated by the overall machine weight with the kneading effect brought by tire elasticity. The core principles can be broken down into the following three points:

1. Static pressure as the compaction foundation

Tire rollers adjust their overall weight (usually 10-30 tons) by adding counterweights (steel sand, water, etc.), and the weight is evenly distributed on multiple rubber tires (common layouts: 3 front and 4 rear, or 4 front and 5 rear), generating continuous static pressure on the ground. This pressure acts on material particles, squeezing them close to each other, reducing gaps between particles, and forming an initial dense structure. The principle is similar to that of static smooth-wheel rollers, but the contact between tires and the ground is flexible, resulting in more uniform pressure distribution.

2. Elastic kneading enhances compaction

Rubber tires have elasticity; during operation, tires will slightly compress as the material deforms, and the friction between tires and materials will drive surface particles to produce tiny horizontal displacement (kneading effect). This kneading effect enables material particles to displace both horizontally and vertically, filling the tiny gaps that static pressure cannot reach. Especially for cohesive materials such as asphalt mixtures, it allows aggregates to better interlock with asphalt binder, avoiding "compaction blind spots".

3. Self-adjusting pressure characteristic

When a tire roller travels on an uneven pavement or an area with uneven material hardness, the tires will automatically deform to adapt to the contact surface, keeping the ground contact pressure of each tire relatively stable. Unlike steel-wheel rollers, it will not generate concentrated pressure due to local protrusions (causing material crushing) nor insufficient pressure due to depressions (leading to substandard compaction), ensuring uniform compaction effect.

II. Pavement Materials Suitable for Compaction by Tire Rollers

The compaction characteristics of tire rollers determine that they are more suitable for materials requiring cohesiveness, uniform density, and high surface flatness, mainly including:

1. Asphalt mixture pavements (core applicable materials)

This is the main application scenario of tire rollers, including hot-mix asphalt mixtures (HMA), modified asphalt mixtures, SMA (stone matrix asphalt), etc.:

• Initial compaction stage: Can be used with double-drum rollers, using the kneading effect to stabilize the mixture and prevent aggregate displacement;

• Re-compaction stage: As the main equipment, it makes asphalt binder fully coat aggregates through kneading, improving the density and bonding strength of the mixture, and reducing the risk of cracks and looseness after the pavement is opened to traffic;

• Final compaction stage: Can eliminate wheel tracks left by steel-wheel rollers, making the pavement surface smoother and improving driving comfort. It is especially suitable for large-stone asphalt mixtures (such as ATB asphalt-treated base), where kneading allows gaps between large aggregates to be filled with fine materials, avoiding aggregate crushing caused by steel-wheel compaction.

2. Cement-stabilized soil/lime-stabilized soil bases (semi-rigid bases)

For semi-rigid base materials such as cement-stabilized crushed stone and lime-fly ash stabilized soil, the kneading effect of tire rollers can make particles inside the base interlock more tightly, while avoiding the problems of "peeling" and "looseness" on the base surface caused by high-frequency vibration of steel-wheel rollers. It is usually used in the initial compaction of the base (after grading by a grader), cooperating with the deep compaction of single-drum rollers to balance the deep bearing capacity and surface flatness of the base.

3. Graded crushed stone/gravel bases

Graded crushed stone bases require an interlocking structure between particles. The flexible compaction of tire rollers allows crushed stone particles to interlock with each other without damaging the edges and corners of crushed stones (steel-wheel vibration may break the edges and corners of crushed stones, affecting the interlocking effect). It is especially suitable for the compaction of graded crushed stone subbases or bases of expressways and first-class highways.

4. Surface compaction of fill subgrades (auxiliary role)

In the last layer of subgrade filling (usually 0-30cm), tire rollers can be used with single-drum rollers to make the subgrade surface dense and uniform through kneading, reducing the settlement difference between the subgrade and the pavement base, and avoiding reflective cracks on the pavement. However, it is not suitable for deep compaction of subgrades (no vibration function, limited compaction depth).

III. Inapplicable Material Types

Tire rollers also have clear application boundaries, and they are not suitable for compacting the following materials:

• Highly cohesive clay subgrades: Clay particles are fine and have strong cohesiveness; the kneading of tires tends to form a "hard shell" on the surface while the interior remains loose. Protruded-block rollers (sheep-foot rollers) should be used with single-drum vibratory rollers;

• Thin-layer cement concrete surfaces: Rigid materials do not require kneading, and tires are easy to stick to cement paste, affecting the flatness of the surface;

• Rubble fill subgrades: Rubble has large particle size and high hardness; tires cannot generate enough pressure to interlock rubble. Single-drum vibratory rollers or impact rollers should be used.