Abstract: The load-bearing mechanism and failure envelope behavior of pile foundation under combined horizontal load and moment load were investigated through centrifugal model tests. Analysis on the results revealed that the failure envelope shape of pile foundation under horizontal load and moment load is an ellipse approximately, and the failure envelope equation can be expressed by elliptic equation. The failure envelope, which can be used to inspect the limit instability of pile foundation, provides a basis to inspect the safety of pile foundation under horizontal load and moment load. The interaction between horizontal load and moment load must be considered in the design of pile foundation. 

Key words:  pile foundation, centrifugal model test,  combined load, bearing capacity, failure envelope