Inner skin friction of open-ended piles considering the degree of soil plugging

This paper presents an experimental study of the plugging effect on the capacity of open-ended piles installed in sandy soil. Full-scale tests, including dynamic and static axial-compression load tests, were carried out on three instrumented piles with different diameters (508.0, 711.2 and 914.4 mm). To measure the outer and inner shaft resistances acting on the piles, a double-walled system was utilized with instrumented strain gauges on the outside and inside walls of the pile. The results of field tests show that the inner shaft resistance was mostly mobilized at the location between the pile tip and 18-34% of the total plug length. It was found that the soil plugging in the lower portion has influence on the inner shaft resistance. In addition, a new design approach that can predict the degree of soil plugging and the inner skin friction is proposed. Based on the plugging measurements, a linear relationship between the PLR and incremental filling ratio (IFR) was proposed. Based on the results of the full-scale field pile load tests, the inner skin friction of the open-ended piles was proposed as a function of the IFR and pile diameter. The proposed method can predict the degree of soil plugging and the inner skin friction of open-ended piles and be selected as convenient option in engineering field.