Brian B. Sheil

Pile Group Settlement Estimation: Suitability of Nonlinear Interaction Factors

In this paper, predictions of pile settlement determined by appropriate superposition of two-pile interaction factors are compared with those computed from continuum analysis. A finite-element package is used in conjunction with the nonlinear Hardening Soil model and the pile group sizes studied are larger than in previous research. The study is presented in two phases: (1) examination of the modulus variation within the group allowing the elimination of some variables, and (2) comparison of pile settlement predictions in the context of the significant variables. The research shows that predictions using the former approach match the continuum analyses very closely for friction piles and reasonably well for end-bearing piles, and show potential for reducing computational time and effort in such problems. The paper also distinguishes between alternative definitions of interaction factor and shows that most accurate predictions arise from interaction factors calculated when only one of the two piles is loaded.

A practical approach for the consideration of single pile and pile group installation effects in clay: Numerical modelling

The first author gratefully acknowledges the College of Engineering and Informatics, NUI Galway, and the University of California Education Abroad Program for funding this research. In addition, the authors gratefully acknowledge the GeoEngineering department at Massachusetts Institute of Technology who compiled and provided the authors with the MITS1 dll for this research.

Real-Time Monitoring of Large-Diameter Caissons

Large-diameter open caissons are a widely-adopted solution for deep foundations, underground storage and attenuation tanks, pumping stations, and launch and reception shafts for tunnel boring machines. The sinking process presents a number of challenges including maintaining verticality of the caisson, controlling the rate of sinking, and minimizing soil-structure frictional stresses through the use of lubricating fluids. A bespoke monitoring system has been developed at University of Oxford to provide early warning of adverse responses during the sinking phase (e.g. excessive soil-structure interface friction). The monitoring system was trialled on a recent pilot project in the UK involving the construction of a 32 m internal diameter, 20 m deep reinforced concrete caisson. This paper describes the monitoring system that was developed and its impact on the construction process of the pilot project. Early indications are that real-time feedback of live construction data has a major impact on the efficiency and safety of the construction process.

Numerical Simulations of Wave–Structure–Soil Interaction of Offshore Monopiles

AbstractOcean energy converters (OECs) are becoming a more popular source of electricity generated from the ocean. The main obstacle associated with the use of OECs is their high initial installation cost. In light of this, geotechnical engineers have been challenged with revisiting the foundation system, aiming toward more economical design. In this study, finite-element (FE) modeling was used to examine the influence of wave-induced lateral loads on a monopile, a common foundation system for OECs, where wave–structure–soil interaction was considered explicitly. Measured data were used to arrive at two different wave scenarios in conjunction with both regular and irregular wave-surface profiles; the wave-induced lateral forces on the monopile foundation were calculated for each case using diffraction theory and used as input loads in the FE model. A parametric study was then undertaken to examine the influence of a range of wave characteristics and pile/soil parameters on monopile response. The results o...

Biaxial loading of offshore monopiles: numerical modelling

AbstractIn this study, finite-element (FE) modeling was used to examine the influence of biaxial lateral loading of a monopile foundation. Two different soil models were adopted to investigate the influence of state-dependent and anisotropic behavior of soil on monopile response. A series of analyses was carried out in which both cyclic and static lateral loads were applied to the pile. Results show that biaxial loading significantly influenced the pile-head load-displacement response in addition to the development of significant accumulated displacements and coexistent soil loosening and densification. Moreover, predictions determined using a state-independent soil model were shown to be significantly nonconservative; these findings have important implications for environmental loading of offshore monopiles.