As the offshore energy industry begins to develop wind farms in areas of deeper water, the use of traditional foundations such as shallow foundation and driven hollow steel tube piles becomes uneconomical. The deployment of floating turbines and continued development of novel/efficient anchoring systems for these structures will be an important factor in the continued growth of the sector. This paper presents an investigation carried out as part of a proof-of-concept for a novel “bi-wing anchor”. This design will allow a plate anchor to be dropped through the water column and then penetrate the seabed under its own weight. The anchor will then be dragged causing it to embed further into the seabed and provide a greater holding capacity. This paper focuses on experimental as well as analysis of the drag embedment behaviour during the installation and pullout phases. The physical modelling investigations were carried out in a transparent clay-surrogate which enabled observation of the anchor’s orientation during installation. The predictions using analytical modelling showed good agreement with the observed behaviour at varying embedment ratios.

This paper presents data from an initial development stage of an 'umbrella anchor' concept. The anchor can be pushed into a sand deposit in a folded arrangement to reduce installation loads. When a pull-out load is applied to the mooring line, the anchor deploys to create a large embedded plate anchor. Physical modelling was carried out in a saturated sand bed with the anchor installed at depths of up to 1.6 m and loaded vertically. During installation, liquefaction was generated at the tip of the anchor to reduce the penetration resistance. This enabled the anchor to be installed quickly and accurately to a target depth. The anchor could provide pull-out resistances comparable to an anchor that has been wished-in-place at similar depths. The observed behaviour provided encouraging preliminary results and suggests that, with further development and analysis, the concept could potentially be used for commercial applications.

Offshore wind turbines are subjected to significant environmental loads from a combination of current, wind and wave action. Under such conditions, the directions of these environmental loads vary over the service life of the structure and therefore the cyclic lateral loading on the foundation also changes direction. The work reported in this paper examines the effects of multi-directional loading on the performance of offshore wind turbine monopile foundations. Tests were carried out in a model sand bed and a mobile loading platform was manufactured to apply loading on the pile in various directions. Tests were also carried out where the cyclic loading was applied under both one-way and two-way loading. The observations indicate significant differences in the stiffness of monopiles between uni-directional and multi-directional lateral cyclic loading. Multi-directional lateral cyclic loading generally results in higher displacements and lower stiffness compared to uni-directional loading, most likely due to shear deformation of a larger volume of soil mass adjacent to the pile.

A large portion of the Irish railway network contains earthworks that were poorly constructed mainly because they were built over 100 years ago when scientific understanding of soil behaviour was not nearly as advanced as it is today. Also, engineers involved in the construction of these structures had to work with often unsuitable local materials as sound bulk fill was not able to be transported significant distances. In order to improve the information obtained from site investigation of these poorly constructed earthworks a number of authors have recently suggested complimenting direct geotechnical investigations with a non-invasive geophysical assessment. In addition to providing a review of the factors which cause failure of earthworks, this paper also discusses the capabilities of three geophysical techniques, Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Multichannel Analysis of Surface Waves (MASW) for assessing the stability of railway earthworks. Examples of the use of each technique are provided from forensic investigations into railway earthwork slope failures in Ireland.

A geophysical investigation was carried out after the failure of an important railway embankment in the south-east of Ireland, The embankment, which had a long-term history of stability problems, was studied using a combination of ground-penetrating radar (GPR), electrical resistivity tomography (ERT), multichannel analysis of surface waves (MASW) and geotechnical testing. A significant thickening of the ballast layer around the failure location was observed using GPR, which confirmed the existence of an ongoing stability problem in the area. ERT profiles determined the presence and spatial extent of a significant layer of soft clay both beneath and to the east of the embankment, which could have a major impact on its long-term stability. ERT also detected steeply sloping bedrock close to the failure zone that is likely to have contributed to the long-term settlement of the embankment, which necessitated frequent re-ballasting. MASW confirmed the presence of the steeply sloping bedrock in addition to determining the low stiffness (G_max) values of the embankment fill. High quality sampling of the soft clay deposit was undertaken and strength and compressibility tests revealed the importance of this layer to both the on-going serviceability problems evident for the original embankment and the stability problems encountered by the remodelled section.