Abstract: The theoretical method for calculation of the negative skin friction resistance of PHC pipe pile is difficult to obtain reliable results due to many complex factors, such as soil properties and consolidation conditions. Therefore, the distribution of negative skin friction and the position of neutral plane can only reliably be obtained by the field loading test by monitoring the internal force distributions. Based on summarizing the limitation of point measurement method of stress and strain, this paper presents a case study of a modified line measurement technique to be used in the negative skin friction in the PHC pipe pile. According to the characteristics of PHC pipe pile, a new method of postimplantation survey line was proposed to effectively resolve the difficulties in the negative skin friction field measurement in the PHC pipe pile. Through the regression data process, the measured strain and the average elastic modulus in the pile shaft under different load levels were obtained, which ensures the reliability of calculation of the axial force and the skin friction. It was shown from the results in the field test that the new field test method and calculation method of negative skin friction are very effective for the PHC pipe pile negative skin friction measurement.

Key words: negative skin friction, phc pipe pile, linear measurement method, skin friction distribution: axial force distribution