Torsional vibration of open-ended pipe piles in saturated soil considering the construction disturbance

A soil-pipe pile-inner soil torsional dynamic interaction model is developed accounting for the radial in-homogeneity of the outer saturated soil as well as the soil plug (inner soil) due to the construction disturbance. Both the outer and inner saturated soils are divided into a series of annular zones in the radial direction with linearly varying soil properties from zone to zone. The governing equation of motion for each soil zone is established based on the Biot's two-phase linear theory and is solved to derive the circumferential shear stress at the pipe pile-soil interface in conjunction with the continuous conditions at the interface of adjacent soil zones. Further, the governing equation for the open-ended pipe pile is established and is solved to derive an analytical solution for the torsional vibration of the pile in the frequency domain. The developed solution is validated against the results of available analytical solutions. The validated solution is then used to examine the torsional vibration characteristics of the open-ended pipe pile under different saturated soil parameters and construction disturbance conditions. The results show that: (1) The pile resistance to torsional dynamic load is enhanced as the soil strengthening range or degree increases, while is reduced as the soil porosity, soil weakening range or degree increases; (2) The inner soil contributes a lot to the enhancement of pile torsional resistance.