A soil displacement pile for forming a composite pile column, the soil displacement pile comprising: a lead comprising: a lead shaft; and at least one lead soil displacement assembly attached at least partially to the lead shaft, the at least one lead soil displacement assembly including; an upper helical plate having an outer edge portion and a central opening defining an inner edge portion; a lower helical plate having an outer edge portion and a central opening defining an inner edge portion, wherein the lower helical plate is spaced a predefined distance from the upper helical plate along a longitudinal axis of the soil displacement assembly; and a curved soil displacement plate having a first edge portion attached to the upper helical plate and a second edge portion attached to the lower helical plate such that a convex surface of the curved soil displacement plate forming a soil contacting surface extends from the inner edge portions of the upper helical plate and the lower helical plate to the outer edge portions of the upper helical plate and the lower helical plate, and such that the convex surface is oriented to contact soil when the soil displacement assembly is driven into the soil to displace the soil from the inner edge portions of the upper helical plate and the lower helical plate toward the outer edge portions of the upper helical plate and the lower helical plate so as to create a cavity in the soil; and at least one extension comprising: an extension shaft; and at least one extension soil displacement assembly attached to the extension shaft. a lead comprising: a lead shaft; and at least one lead soil displacement assembly attached at least partially to the lead shaft, the at least one lead soil displacement assembly including; an upper helical plate having an outer edge portion and a central opening defining an inner edge portion; a lower helical plate having an outer edge portion and a central opening defining an inner edge portion, wherein the lower helical plate is spaced a predefined distance from the upper helical plate along a longitudinal axis of the soil displacement assembly; and a curved soil displacement plate having a first edge portion attached to the upper helical plate and a second edge portion attached to the lower helical plate such that a convex surface of the curved soil displacement plate forming a soil contacting surface extends from the inner edge portions of the upper helical plate and the lower helical plate to the outer edge portions of the upper helical plate and the lower helical plate, and such that the convex surface is oriented to contact soil when the soil displacement assembly is driven into the soil to displace the soil from the inner edge portions of the upper helical plate and the lower helical plate toward the outer edge portions of the upper helical plate and the lower helical plate so as to create a cavity in the soil; and a lead shaft; and at least one lead soil displacement assembly attached at least partially to the lead shaft, the at least one lead soil displacement assembly including; an upper helical plate having an outer edge portion and a central opening defining an inner edge portion; a lower helical plate having an outer edge portion and a central opening defining an inner edge portion, wherein the lower helical plate is spaced a predefined distance from the upper helical plate along a longitudinal axis of the soil displacement assembly; and a curved soil displacement plate having a first edge portion attached to the upper helical plate and a second edge portion attached to the lower helical plate such that a convex surface of the curved soil displacement plate forming a soil contacting surface extends from the inner edge portions of the upper helical plate and the lower helical plate to the outer edge portions of the upper helical plate and the lower helical plate, and such that the convex surface is oriented to contact soil when the soil displacement assembly is driven into the soil to displace the soil from the inner edge portions of the upper helical plate and the lower helical plate toward the outer edge portions of the upper helical plate and the lower helical plate so as to create a cavity in the soil; and at least one extension comprising: an extension shaft; and at least one extension soil displacement assembly attached to the extension shaft. an extension shaft; and at least one extension soil displacement assembly attached to the extension shaft.