Approximately 90% of the land surface on earth is covered with loose, unconsolidated materials, such as soil, clay, silt, sand, gravel, and boulders, which varies in depth from only centimetres, to hundreds of metres. Drilling through this so-called overburden is often problematic, due to the tendency of the earth to cave in behind the drill bit. This makes it difficult to retrieve the drill string after the hole has been drilled. In practice, the borehole is often lost before a casing tube can be inserted to support it. Symmetrix drilling offers a solution to drill in these difficult conditions.