Field study on the shaft capacity of pre-bored grouted planted pile embedded in deep soft soil

This paper presents a group of field tests to investigate the shaft capacity of pre-bored grouted planted (PGP) pile embedded in deep soft soil. Totally three test PGP piles were designed for the static load tests. The fiber optic sensors were equipped along the PHC pile shaft of two test piles to investigate the reliability and accuracy of fiber optic sensors on measuring the axial force of PGP pile. The diameter of cemented soil column of test PGP pile was 560 mm, and the diameter of core PHC pipe pile was 400 mm. The thickness of cemented soil layer around the PHC pipe pile reached 80 mm. The test results showed that: the base capacity of three test piles were all not fully mobilized when loaded to the designed ultimate capacity 3000 kN, and the base capacity of test pile TP1 and TP2 were 14.4% and 14.8%, respectively of the applied pile head load when loaded to 3000 kN. The skin friction of cemented soil–soil interface was fully mobilized when the pile–soil relative displacement reached 10 mm, 1.8% D (D is pile diameter). The measured ultimate skin friction of test pile TP1 and TP2 in different soil layers were 1.21–1.88 times of the recommended ultimate skin friction of bored pile, which can be used for the design of PGP pile in following engineering projects. The increase of cemented soil layer thickness (increase of pile diameter) could increase the entire shaft capacity of PGP pile, on the condition that the core PHC pile and cemented soil layer act as a unit in the load transfer process.