Abstract：Based on the static load test and stress measurement of overlength piles in deep soft soil foundation，the load transfer mechanism and bearing behavior of overlength piles under heavy load have been studied. Under heavy load，the overlength piles behave as end-bearing frictional piles，and their frictional resistance and end resistance are asynchronous and coupling. The slime affects the exertion of frictional resistance and end resistance，so it is necessary to clear up the slime of overlength piles¢ bottom under heavy load. At the same time，the frictional resistance will be degraded. The critical value of pile-soil relative displacement has a good correlation with settlement of pile top，and it is a function of pile diameter. When the settlement of overlength piles¢ top exceed (0.01-0.02)D in soft soil，the soil around pile will slide. Some suggestions for design and appliance of overlength piles have been discussed farther on the bearing mechanism；and guidances for theoretical research and technical design of overlength piles have been provided.
