When a PHC pipe pile is driven into the ground

the lateral pressure provided by the soil plug may lead to hoop failure of the PHC pipe pile.In this paper

the mechanical model of the expansion effect of soil plug is established

and the quantitative analysis is carried out.Considering the disturbance of piling

the soil plug is divided into wedged zone and unwedged zone

and an improved one-dimensional equilibrium equation of soil plug is derived.The cylindrical cavity expansion theory is used to explain the compaction effect of PHC piles.It is assumed that the external soil is in elastoplastic state

and the expressions of radius of plastic zone and lateral earth pressure which consider initial stress are deduced.According to the Lame solution of axial symmetrical ring

the rule to judge hoop failure is given.At last

the rationality of the model presented in this paper is verified by a practical example.In-situ test results of hoop stirrup strain indicate that the model can quantitatively describe the hoop failure mechanism of PHC pipe piles

and can be useful for checking calculation of hoop tensile resistance.