Fig. (4) Comparison of the results of this paper with those from [21] and [9]: (a) the comparison of the axial force of the pile with that of Niumpradit & Karasudhi [21]; (b) the comparison of the axial force of the pile with that of Ai et al., [9]; (c) the comparison of the non-dimensional vertical displacement of the pile with that of Ai et al., [9].