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The pre-bored grouted planted (PGP) pile shaft consists of a core PHC pile and the surrounding cemented soil column. The shaft capacity of PGP pile is controlled by the PHC pile–cemented soil–soil interface. In this paper, the effect of curing time on the frictional capacity of smooth concrete pipe pile–cemented soil interface was investigated through pile–soil interface shear tests. The test results show that the peak skin friction of pipe pile–cemented soil interface increased with the curing time. Nevertheless, the normalized peak skin friction (peak skin friction/cemented soil strength) of interface decreased with the curing time. The thickness of the cemented soil layer had a large effect on the residual skin friction of pipe pile–cemented soil interface. The scale effect also existed in the smooth concrete pipe pile–cemented soil interface shear tests, as the stiffness and shear strength of interface would decrease with the pipe pile diameter, which would eventually induce the decrease of radial confining pressure of the interface. [ABSTRACT FROM AUTHOR]

A group of field tests and three-dimensional finite element simulation were used to investigate the behavior of the pre-bored grouting planted pile under compression and tension; moreover, a group of shear tests of the concrete-cemented soil interface was carried out to study the frictional capacity of the pile-cemented soil interface. The load-displacement response, shaft resistance and mobilized base load were discussed based on the measured and computed results. The measured and computed results show that the frictional capacity of the cemented soil-soil interface is better than the frictional capacity of the concrete-soil interface. The frictional capacity of the concrete-cemented soil interface is mainly controlled by the properties of the cemented soil, and the ultimate skin friction of the concrete-cemented soil interface is much larger than that of the cemented soil-soil interface. The frictional capacity of the soil layer close to the enlarged base is also promoted because of the compaction of the enlarged base. The enlarged cemented soil base can promote the behavior of the pile foundation under tension, and the enlarged cemented soil base undertakes approximately 26.3% of the total uplift load under the ultimate bearing capacity in this research. [ABSTRACT FROM AUTHOR]