The effect of cemented soil strength on the frictional capacity of precast concrete pile–cemented soil interface

Abstract

The pre-bored grouted planted (PGP) pile is a composite pile consisting of a precast concrete pile and the cemented soil around the pile. Thus, the PGP pile shaft capacity is affected by the pile–cemented soil interface and the strength of the cemented soil formed around the pile. In this paper, a series of shear tests were conducted to investigate the frictional capacity of the precast concrete pile–cemented soil interface, and the strength of cemented soil and its effect on the interface frictional capacity. The test results show that the frictional capacity of precast pipe pile–cemented soil interface is largely dependent on the cemented soil strength, and the peak skin friction of the interface increases from 7.58 to 204 kPa with the cemented soil strength increasing from 65 to 1500 kPa. An adhesion factor is proposed to correlate the peak skin friction of the precast pipe pile–cemented soil interface and cemented soil strength. The adhesion factor is found to range from 0.116 to 0.141 corresponding to the range of cemented soil strength from 65 to 1500 kPa. It was also noted the failure at the pile–cemented soil interface is brittle. The scale effect also exists in the pile–cemented soil interface shear test, and the scale effect factor is 1.9 when the pile diameter decreases from 85 to 37 mm. Accordingly, the design of PGP pile should avoid approaching the frictional capacity of the pile–cemented soil interface.