Which of the following would increase the frequency of a vibratory roller?

Increasing the speed of rotation of the eccentric weight would indeed enhance the frequency of the vibratory roller. The vibratory roller operates based on the principle of applying a vibration to the roller drum, which is achieved through the rotation of the eccentric weight. When the speed of this rotation is increased, it results in a higher frequency of vibrations being applied to the surface being compacted.

This is important in asphalt compaction because a higher frequency typically leads to a more effective compaction process. It can help in achieving greater density and stability in the asphalt layer by eliminating air voids more efficiently.

The other factors mentioned, while they may affect the overall impact and efficiency of the roller, do not specifically increase the frequency of operation in the same direct manner. For instance, moving the eccentric weight farther from the center or increasing the mass of the weight could change amplitude and the characteristics of the vibrations, but not the frequency itself. These changes can influence the effectiveness of compaction but do not alter how often the vibrations occur within a given time frame.