Numerical simulation of open ended pile installation in saturated sand

Abstract

Open-ended pipe piles have been the preferred choice for various foundation applications, and in particularly for offshore wind turbines. The need to know, well in advance, certain design parameters prior to installation thus arises, and through numerical analyses, ranges for these installation parameters, and the behavior of the sand surrounding the pile can be estimated. Offshore environment poses an additional challenge of taking into account not only the penetration process and effects of dynamic loading of the sand, but also the pore pressure built up in the soil skeleton. This paper presents a novel approach to simulate the dynamic installation process of open-ended piles in saturated soil. Thus, the simulation also provides the basis to predict the pile behavior due to axial or lateral loading considering the installation effects. By coupling the aspects of Lagrangian and Eulerian methods, a particle-based method, called Material Point Method (MPM), more specifically its extension called Convected Particle Domain Interpolation (CPDI) method has been employed in the present work. To simulate saturated media, an extension of CPDI is incorporated in the form of 2-phase formulation, different velocities for soil and water are considered and thus able to capture precisely the saturated-soil behavior. A 2-D axisymmetric model is considered, along with a penalty method formulation to calculate contact forces between pile and soil. This method, when applied in conjunction with the hypoplastic constitutive model, provides a framework which allows us to study detailed effects of pile installation on the surrounding soil.