Drilled shaft is a deep foundation that is constructed by placing concrete in an excavated hole. It can carry both axial and lateral loads. They are also called as bored piles, piers, drilled piers, caissons, drilled caissons, or cast-in-place piles. To increase the bearing capacity, drilled shafts are commonly socketed into rock. The portion of the shaft drilled into rock is referred to as a rock socket. It can penetrate through soils with cobbles or boulders. They can also be socketed into rock. The diameter or length of the drilled shaft can be easily changed during construction to compensate for unanticipated soil/rock conditions.

Drilling additives increase productivity in a wide range of operations, including flushing the hole, bit mudding, recovering stuck or lost rods, collaring the hole and redrilling caused by hole stuffing. It is used to reduce viscosity and remove clay and sediment from well. It can be used where air/foam drilling methods are allowed.