An experimental program to investigate the behavior of pedestal pile under combinatorial loads in dense sand is put forward through 1oading test and centrifuge test. The work focused on evaluating the shape of failure envelope surface of combinatorial loaded pile. The measured data and phenomenon are discussed. As a result

the following behaviors have been clarified: The failure curve on M=H h plane is an ellipse approximately

which can roughly estimated by an equation from Vm

Hm

and Um. The failure curve on M-H plane also was an ellipse approximately; this ellipse can be determined by results of two laterally loaded pile tests. If Um

Vm

Hm and Mm are known or assumed

the failure envelope surface can be obtained by the equation. The interaction among vertical

lateral and bending load must be considered in the design of pile foundation.