Piles used to stabilize the slope are commonly used in Taiwan. In this study, the FLAC3D program is used to explore the effects of the soil-pile parameters of a landslide stabilizing pile that affects the stability of
the slope. To calculate the safety factor of the slope, the static analysis is conducted using the shear strength reduction method while the seismic analysis uses displacement. The analysis modeled the changes in pile spacing based on the effects of arching and the safety factor of the slope. The results showed that the pile’s clear spacing (Sc) and soil shear strength parameters are critical parameters that affect arching. A wider clear spacing (Sc) of pile makes arching disappear and the pile responds as a single pile. With a larger soil friction angle, arching is more obvious. However,as soil cohesion increases, arching becomes less obvious. The design of the pile spacing and the diameter ratio (S/D) is a crucial factor in the formation of arching effects. This study suggests S/D≦2 should be used for the design of
landslide stabilizing piles. Such landslide stabilizing piles could change the failure mode of the slope from a deep seated landslide to a shallow landslide and the factor of safety of slope reduced.
Key Words : Slope stability, pile foundation, arching effect, seismic design.