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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]

The frictional capacity of pile–cemented soil interface is similar to the frictional capacity of pile–rock interface as the strength of cemented soil is close to the strength of soft rock. A series of pile–soil interface shear tests were carried out to study the frictional capacity of square pile–cemented soil interface. The shear test results show that the peak skin friction of square pile–cemented soil interface decreased with the increase in the side length of square pile; the failure mode of square pile–cemented soil interface was affected by the cemented soil thickness; the peak skin friction of square pile–cemented soil interface would increase with the roughness of square pile surface when the mean size of coated silica sand reached 0.94 mm, and the peak skin friction increased slightly with the density of coating sand. [ABSTRACT FROM AUTHOR]

The pre-bored grouted planted pile is a new type of composite pile foundation that consists of a precast concrete pile and the surrounding cemented soil. A series of shear tests were conducted in a specific shear test apparatus to investigate the shaft capacity of the different pile-soil interfaces. The test results show that the frictional capacity of the cemented soil-sand interface is controlled mainly by the sand properties, while the strength of the cemented soil slightly influences the interface properties by affecting the normalized roughness coefficient Rn. The frictional capacity of the concrete-sand interface is similar to the frictional capacity of the cemented soil-sand interface, and the existence of mud cake layer virtually hampers the frictional properties of the interface. The maximum skin friction of the concrete-cemented soil interface increases approximately linearly with the increasing cemented soil strength, and the value of the maximum skin friction is much larger than that of the cemented soil-sand interface of identical cemented soil strength, which demonstrates the integrity of the pre-bored grouted planted pile in the load transfer process. [ABSTRACT FROM AUTHOR]