4.4.3 Column piles

Column piles used in excavations include the PIP pile，reinforced concrete pile，and the mixed pile.The reinforced concrete pile can be further divided into the reversed pile and the all casing pile.Basically，the stiffness of the reinforced concrete pile is the highest，that of the PIP pile the second，and that of the mixing pile the smallest.For more about the characteristics，strengths and shortcomings，and construction of column piles，see Section 4.2.3.

Column piles bear the axial load and flexural load simultaneously.Therefore，their behavior is similar to that of the reinforced concrete columns.No matter which type of column pile is used，it is necessary to transform the flexural rigidity per pile into that per unit width in a plane strain analysis.The thus obtained bending moment and shear envelopes are then used for the design of reinforced concrete columns.Since the design of the columns is extremely complicated，to save space，this book is not going to further explain this subject.Reader can refer to the design chart of reinforced concrete columns or the American Concrete Institute（ACI）code.