Research on static load test results of compresive and tensile piles in soft soil

In order to study the differences of vertical bearing capacity and load transfer mechanism of single pile under compressive and tensile conditions, compressive and tensile static load tests of bored piles were carried out on a pile foundation project in Shanghai. The results show that due to the partial enlarger of the tensile pile diameter during construction, the pile body cracks and soil shear failure occurs, causing the uplifting displacement to be too large and the bearing capacity has much less than the bearing capacity of compressive piles. The ratio of pile end resistance to pile top load of compressive pile is very small, which the maximum does not exceed 1.5%. Therefore, it is unreasonable to blindly increase the pile length to enter hard soil layer. The pile side friction of compressive piles tends to decrease along the depth direction, and the compressive piles present semi-spindle-shaped distribution law of “large middle and small ends”, so pile side grouting is often adopted in the middle and lower part of the pile section to increase its vertical carrying capacity.