This study performed a series of three-dimensional (3-D) finite element analyses to investigate the stabilization mechanism of the tied-back retaining pile installed at the Yi-Zhuan-No.1 Landslide. Meanwhile, a homogeneous
slope of colluviums and heterogeneous slope of colluviums with bedrock underneath, were established to perform a systematic numerical experiment on various design parameters of the tie-back retaining pile. In numerical
experiments, the design parameters consist of the anchorage length (Lg), inclination () and the spacing ratio (S/D =pile spacing/pile diameter) of retaining pile. According to the numerical experiments, the FS value of a heterogeneous slope is always higher than that of a homogeneous slope and this demonstrates the importance of penetrating the retaining pile into the bedrock (bearing stratum) in the design. Moreover, the FS value greatly decreases as the installation spacing
S value surpasses 8D (S  8D) and this indicates that the arching effect between two adjacent piles immediately
disappears when the spacing of piles is larger than 8 times of pile diameter. In addition, the FS value of homogeneous slope is greatly promoted when the anchorage length Lg increase from 5 to 7 m while it is not the case for heterogeneous slope the increase is very rare. However, the FS values of the two types of fictitious slopes, become unchanged and tend to a constant when the Lg value increases from 7 to 10 m.
Key Words : Three-dimensional (3-D) finite element analyses, Tied-back retaining pile, Anchorage length, Factor
safety of slope stability