Abstract: Besides elastic strain, creep would also occurred in long-term pile stress test represented by pile immersion test in loess regions for concrete pile; and the influence of creep occurred under long-term axial stress was usually be overlooked in the past when calculating stress of pile body. But creep is a real existence, influence degree of creep and how to eliminate its effect are worth studying. Based on comparative analysis of field test data, how the concrete creep affect the analytical results of pile stress is studied; and the conclusion shows that the overlook of concrete creep will lead to wrong distribution rules of axis force and friction. A formula, which calculates axial force of pile and can eliminate the creep influence, is derived from some basic theory on creep. Some measures needing be taken in pile immersion test of loess regions to attain representative creep curve are presented; mainly include: controlling the concrete strength grade of test pile, setting calibration section near pile top and keeping concrete’s temperature and moisture constant in this section and are in the same with lower pile.

Key words: creep of concrete, concrete pile, negative skin friction, collapsible loess, immersion test of pile, stress test