Breyden Lonnie

Bio: Breyden Lonnie is an academic researcher from University of Western Australia. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

Installation And Pull-Out Capacities of Drag-In Plate Anchors

Abstract: The trend towards taut-wire mooring systems, instead of catenary chains, to anchor floating facilities for offshore exploration requires high-capacity anchoring systems capable of withstanding vertical loading components. Conventional drag anchors have very limited vertical capacity, and this has led to the development of alternative drag-in plate anchors, or vertically loaded anchors (VLAs). VLAs are installed in a similar way to conventional drag anchors, but they are ultimately loaded normal to their plate surface, and thus act like embedded plate anchors. A critical issue in the overall mooring system design is the ratio of the pull-out load to the anchor installation load, and this is termed the performance ratio. The performance of a model VLA was modelled in a geotechnical centrifuge, with particular attention to the performance ratios. Whilst the performance ratios obtained were much lower than expected, the testing proved that VLAs provide a simple and inexpensive alternative to other anchoring systems.Copyright © 2002 by ASME

Experimental investigation on the penetration mechanism and kinematic behavior of drag anchors

Abstract: Five fundamental problems closely relevant to the penetration mechanism and kinematic behavior of drag anchors, including the effects of the initial orientation of the anchor, the effects of the shank angle, the penetration direction of the anchor, the relationship between the fluke orientation and the drag angle at the shackle, and the relationship between the drag distance and the anchor displacement in the soil, are investigated in a model experimental system through a specially-designed multi-parameter measurement technique. The kinematic parameters of the anchor, including the drag force, drag angle, drag distance, displacement of the anchor, and pitch and roll of the anchor are measured simultaneously during dragging. By systematically analyzing the kinematic parameters and trajectories of the anchor, further knowledge of the five fundamental problems, which is believed to be beneficial to improving our understanding on the penetration mechanism and kinematic behavior of drag anchors, is clearly obtained. The techniques and methods established in the present work provide a better basis for further research on the fundamental problems of drag anchors.

Movement direction of drag anchors in seabed soils

Abstract: The movement direction of drag anchors is an important property of the anchor and plays a key role for the anchor penetrating seabed soils. However, the generally accepted assumption for the movement direction is too vague to be adopted for a precise analysis. The former work both in numerical and experimental studies demonstrates that there has not been a clear knowledge of the movement direction for the drag anchor with a complicated fluke section. In this paper, an analytical method that is capable of predicting the movement direction of the drag anchor with an arbitrary fluke section is developed. In the analytical study, based on a rational mechanical model for drag anchors and the knowledge of the mechanism that the anchor penetrates and moves in soils, an analytical model that can predict the movement direction of drag anchors with an arbitrary fluke section both in cohesive and noncohesive soils is established. The analytical model is applied to predicting the movement direction of the anchor with rectangular and wedge-shaped sections, and clear prediction results are obtained. Some important features of the movement direction are revealed, especially the step change of the movement direction from the unstable to the stable penetration stages due to the anchor weight. In the experimental study, specially designed model flume tests in saturated sand are performed to detect the movement direction of four anchor models with different fluke sections. Being verifications of the analytical model, the experimental data are employed to compare with the theoretical predictions and the agreement is satisfactory. The present work proves that the movement direction of the drag anchor with an arbitrary fluke section can be reasonably determined by the developed analytical method.

Numerical Simulation of Drag Anchor Installation by a Large Deformation Finite Element Technique

Abstract: Previously published finite element analysis of drag anchors only involved the pullout capacity of the anchor. There are no finite element (FE) simulations of the installation of drag anchors probably because of two restrictions. First, during the anchor installation, the installation line is needed, which is difficult to be simulated in the FE analysis. Second, the anchor installation that involves large deformation of surrounding soils can not be solved using the classical FE method. In the present work, the installation line is constructed by connecting cylindrical units with each other using connector elements. Then it is introduced into the installation of drag anchors, which is simulated by a large deformation finite element analysis using the coupled Eulerian-Lagrangian (CEL) technique. By comparing with theoretical solutions, including the tension and profile of the installation line embedded in soils, and the movement direction, drag force, drag angle and trajectory of the anchor, the FE simulation of the drag anchor installation is well verified. The present study also demonstrates that the CEL technique is effective for simulating the anchor-line-soil interactional problems.Copyright © 2014 by ASME

Model tests and finite element analysis for vertically loaded anchors subjected to cyclic loads in soft clays

Abstract: More attention has been focused on the pull-out behaviour of plate anchors under monotonic loads. Relatively less attention has been focused on the cyclic behaviours of vertically loaded anchors (VLAs) subjected to combined average and cyclic loads in soft clays. Therefore, these anchors are investigated by conducting reduced-scale model tests under 1 g conditions, and the cyclic deformation process of VLAs in soft clays are simulated through a 3D finite element method using an advanced elastoplastic bounding surface constitutive model of soft clays proposed by the authors. The failure displacement of VLAs for the shallow-embedded and deep-embedded conditions was determined by performing monotonic loading tests. The change rules of average and cyclic displacement and the cyclic bearing capacity of anchors with the number of cycles are revealed by performing cyclic loading tests. The influence of the average and cyclic load levels and the embedded depth on the cyclic bearing capacity is clarified. The displacement time, load-displacement histories and cyclic bearing capacity of VLAs can be predicted relatively well through 3D finite element analysis. The significant plastic strain accumulation and nonlinear cyclic hysteresis responses of VLAs in soft clays and the soil flow mechanisms surrounding the plate anchors at failure can be captured.

Profile and Frictional Capacity of a Mooring Line Embedded in Sand via Centrifuge Model Testing

Abstract: The authors present a method for calculating a mooring line’s tension and angle of inclination at the anchor pad eye to analyze the behavior of a mooring line embedded in sand. They adopted the governing equation from a previous study for clay and reanalyzed the frictional and bearing resistances. The authors performed a number of centrifuge tests at two anchor depths while maintaining relative densities of 76 or 51% in the cylindrical test box to validate the proposed analytical method. The analytical solutions agreed well with the test results and the results of the simplified method. The authors conducted a parametric study to evaluate the effects of various factors on the behavior of an embedded mooring line in sand, including the depth of the attachment point, the internal friction angle of sand, the submerged unit weight of sand, the angle of the mooring line on the seabed, and the self-weight and nominal diameter of the mooring line. The results demonstrated that the proposed analytical met...