Pile-soil interaction is considered to be one of the most important problems in the study of the mechanical behaviour of pile foundation. In this paper, the lateral friction resistance and pile-soil relative displacement of bridge piles in deep soft soils are monitored for an extended period by using concrete strain gauges that are embedded in the test pile. Field test results show that both the pile lateral frictional resistance and pile-soil relative displacement increase along with time, while the pile-soil interaction demonstrates a time eff...