Self-Drilling Ground Anchors - Wessel Drilling
2010-2-3 · depth have been completed by the hollow-rod method. The drill string used in hollow-rod drilling is similar to that used in jetting, except that the chisel bit has a ball check valve in it. Water or a clay-water mixture is kept in the annular space between the drill rods and well casing to help prevent the uncased portion of the hole from collapsing.
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