Skin friction resistance of expansion steel pipe piles in sandy soils

摘要

This study investigates the use of expansion steel pipe piles for the reinforcement of relatively loose (sandy) soil under small building foundations. The expansion steel pipe piles used in this study are frequently used as rock bolts in tunnel excavation in Europe. The diameter of these pipes expands from 36 to 54 mm through the application of high‐pressure water. In this study, field load tests confirm the reinforcement effect of expansion steel pipe piles. The results can be summarized as follows: (a) The region of the surrounding soil compressed by the expansion of the piles is approximately 8 times (450 mm) the pipe diameter, as measured from the pile center. (b) The maximum friction resistance of the expansion steel pipe piles is approximately 3 times greater than that of conventional steel pipes with the same diameter. (c) The finite cavity expansion theory was used to estimate the maximum friction resistance, and the analytical results correlate strongly with the field test results. The authors are focusing on the outer‐diameter expansion of expansion steel pipe and are researching and developing ground reinforcement piles for small‐scale buildings. This paper summarizes the results of experiments and theoretical analysis that investigated the effects of increasing the skin friction resistance through outer‐diameter expansion. We confirmed that the maximum friction force per unit area of the expansive steel pipe piles was 2.7‐3.0 times that of the single pipes with the same diameter (straight pipes with open ends).