Colorado Geology & End Bearing Helical Piles on Bedrock

Colorado has a diverse geology including alluvial, colluvial, and eolian deposits overlying sedimentary, metamorphic, and igneous bedrock at varying depths and outcrops. There is often concern for helical piles bearing on bedrock in these soil profiles, particularly if the bedrock is sloping or too hard to penetrate. Though it has been accepted for a long time that helical pile axial capacity is correlated with installation torque, there are sometimes concerns regarding helical piles that refuse or “spin-out” on bedrock without meaningful torque readings. This paper covers common practices in the industry for design of helical piles end bearing on bedrock. Hardness of bedrock and penetrability of helical piles into bedrock are presented. Design choices that can be used to help improve penetration are discussed. Common approaches to estimate capacity of helical piles that “spin-out” and other concerns for helical piles end bearing on bedrock are described.