Sonic drilling is a soil penetration technique that strongly reduces friction on the drill string and drill bit due to liquefaction, inertia effects and a temporary reduction of porosity of the soil. The combination makes penetrating a large range of soils easy for Gregg’s sonic rigs and tooling. When drilling with a sonic drill head, the entire drill string is brought to a vibration frequency of up to 150 Hz. This causes a very thin layer of soil particles directly surrounding the drill string and bit to loose structure. Instead of a stiff mass, the soil behaves like a fluid powder or paste. This fluidization, or liquefaction, dramatically reduces friction. In alluvial material, vertical vibrations are generally enough to drive down a drill string for many meters without the injection of any water or air. When you are drilling in hard formations, liquefaction cannot take place. In such cases you can combine vibration with rotation, and use rock drill bits to cut the material.