Abstract: To enhance the bearing capacity of plastic tube cast-in-place concrete pile (TC pile), the plastic tube cast-in-place concrete pile with shaft pre-grouting (TCSG pile) was developed in combination with the technology of shaft grouting. The in-situ static load tests were carried out on the TCSG pile, TC pile, and plastic tube cast-in-place concrete pile with large diameter (TCLD pile) installed in different times. Meanwhile, three kinds of calculation models of single pile settlement were introduced to predict the piles settlement. The testing and calculating results indicate that the bearing capacity of TCSG pile is raised by 8.3%-20.0% with a settlement decreased by 19.8%-33.5%; while the bearing capacity of TCLD pile is reduced by 10.0%-16.7% with a settlement increased by 13.2%-43.8%; compared with TC pile; the ratio of axial force attenuation of TCSG pile is greater than that of TC pile or TCLD pile; the difference is trivial between the average ratios of axial force attenuation for TCSG pile respectively obtained in earlier and later static load tests; the average ratio of axial force attenuation of TC pile gained in the later static load test is increased by 1.1%-14.2% compared with that in earlier static load test; while a reduction of 5.9%-21.9% in the average ratio of axial force attenuation is found in TCLD pile; the average skin frictions of TCSG pile under each loading level, compared with TC pile, increase by 14.5%-39.6% and 9.2%-28.6% during the earlier and later static load tests, respectively; while those of TCLD pile decrease by 4.9%-11.8% and 11.5%-30.7% due to enlarging the diameter of TCLD pile; the increasing of bearing capacity of TCSG pile with time is insignificant; the skin friction of TCLD pile diminishes with time elapsing; in contrast, the end resistance of TCLD pile increases; the calculation model of single pile settlement based on the pile-soil load transfer can well predict the settlement of a single plastic tube pile.

Key words: plastic tube cast-in-place concrete pile with shaft pre-grouting, pre-grouting, bearing characteristics, time effect, calculation model of single pile settlement