Undrained capacity of offshore axially loaded piles with the CSUH model incorporating cylindrical cavity theory

Axially loaded piles are widely employed in deep-water offshore platforms, offshore wind turbine foundations, electrical-transmission towers, and bridge piers, and other structures to support axial loads. This paper presents a semi-analytical solution for predicting the undrained response of axial load piles using the unified hardening model for clays and sands (CSUH), incorporated within the framework of the cylindrical cavity theory. The soil around the pile is idealized as a cylindrical cavity. By combing the stress equilibrium equation, compatibility equation, boundary conditions, and the constitutive model, the soil state around the pile during loading is described as a system of first-order ordinary differential equations (ODEs) with unknown variables, which are solved as an initial value problem. The derived load-displacement (t-z) curve is then incorporated into the compression differential equation to determine the undrained capacity of the axially loaded piles. The proposed approach is validated with finite-element numerical simulation results. Additionally, results from a centrifuge test and a field test are compared with those predicted by the proposed approach. The comparisons demonstrate that the present approach can accurately predict the undrained load-displacement behavior of axially loaded piles, and capture key phenomena observed in pile tests.