Test Research on the Development of Negative Skin Friction on Piles under Vertical Loads and Surcharges

Abstract

To study the development of negative skin friction on piles, a field test on three identical piles was carried out. In the test, the loads on pile top were added first, and then ground surcharges were applied while the pile top settlement was stable. According to the test results, additional settlement induced while surcharges became larger, the additional settlement rates of piles increased with the increase of the load at the pile top at the initial stages of the surcharge. The increasing speed of the additional stress of the upper part of the pile slowed down while the load at the pile top increased. The increase of the load at the pile top postponed the appearance of negative skin friction. At the testing stage, the negative skin friction that surrounded the piles increased as the loading time continued. In all levels of the loads, the neutral point position moved down as the loading time continued. The steady neutral point position moved up with the increase of the load at the pile top. The fitting curve matches well with the test result.