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Journal articleDoherty P, Igoe D, Murphy G, et al., 2015,
Field validation of fibre Bragg grating sensors for measuring strain on driven steel piles
, GEOTECHNIQUE LETTERS, Vol: 5, Pages: 74-79, ISSN: 2049-825X- Author Web Link
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- Citations: 35
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Journal articlevan Reeuwijk M, Hadziabdic M, 2015,
Modelling high Schmidt number turbulent mass transfer
, INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, Vol: 51, Pages: 42-49, ISSN: 0142-727X- Author Web Link
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- Citations: 16
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Journal articleWhittaker AC, Walker AS, 2015,
Geomorphic constraints on fault throw rates and linkage times: Examples from the Northern Gulf of Evia, Greece.
, Journal of Geophysical Research: Earth Surface, Vol: 120, Pages: 137-158, ISSN: 2169-9003 -
Journal articleCraske J, van Reeuwijk M, 2015,
Energy dispersion in turbulent jets. Part 2. A robust model for unsteady jets
, Journal of Fluid Mechanics, Vol: 763, Pages: 538-566, ISSN: 0022-1120In this paper we develop an integral model for an unsteady turbulent jet that incorporates longitudinal dispersion of two distinct types. The model accounts for the difference in the rate at which momentum and energy are advected (type I dispersion) and for the local deformation of velocity profiles that occurs in the vicinity of a sudden change in the momentum flux (type II dispersion). We adapt the description of dispersion in pipe flow by Taylor (Proc. R. Soc. Lond. A, vol. 219, 1953, pp. 186–203) to develop a dispersion closure for the longitudinal transportation of energy in unsteady jets. We compare our model’s predictions to results from direct numerical simulation and find a good agreement. The model described in this paper is robust and can be solved numerically using a simple central differencing scheme. Using the assumption that the longitudinal velocity profile in a jet has an approximately Gaussian form, we show that unsteady jets remain approximately straight-sided when their source area is fixed. Straight-sidedness provides an algebraic means of reducing the order of the governing equations and leads to a simple advection–dispersion relation. The physical process responsible for straight-sidedness is type I dispersion, which, in addition to determining the local response of the area of the jet, determines the growth rate of source perturbations. In this regard the Gaussian profile has the special feature of ensuring straight-sidedness and being insensitive to source perturbations. Profiles that are more peaked than the Gaussian profile attenuate perturbations and, following an increase (decrease) in the source momentum flux, lead to a local decrease (increase) in the area of the jet. Conversely, profiles that are flatter than the Gaussian amplify perturbations and lead to a local increase (decrease) in the area of the jet.
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Journal articleYang ZX, Jardine RJ, Guo WB, et al., 2015,
A new and openly accessible database of tests on piles driven in sands
, Géotechnique Letters, Vol: 5, Pages: 12-20, ISSN: 2045-2543 -
Journal articleMagee C, Duffy OB, Purnell K, et al., 2015,
Fault-controlled fluid flow inferred from hydrothermal vents imaged in 3D seismic reflection data, offshore NW Australia
, Basin Research, Vol: 28, Pages: 299-318, ISSN: 1365-2117Fluid migration pathways in the subsurface are heavily influenced by pre-existing faults. Although studies of active fluid-escape structures can provide insights into the relationships between faults and fluid flow, they cannot fully constrain the geometry of and controls on the contemporaneous subsurface fluid flow pathways. We use 3D seismic reflection data from offshore NW Australia to map 121 ancient hydrothermal vents, likely related to magmatic activity, and a normal fault array considered to form fluid pathways. The buried vents consist of craters up to 264 m deep, which host a mound of disaggregated sedimentary material up to 518 m thick. There is a correlation between vent alignment and underlying fault traces. Seismic-stratigraphic observations and fault kinematic analyses reveal that the vents were emplaced on an intra-Tithonian seabed in response to the explosive release of fluids hosted within the fault array. We speculate that during the Late Jurassic the convex-upwards morphology of the upper tip-lines of individual faults acted to channelize ascending fluids and control where fluid expulsion and vent formation occurred. This contribution highlights the usefulness of 3D seismic reflection data to constraining normal fault-controlled subsurface fluid flow.
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SoftwarePiggott MD, 2015,
OpenTidalFarm
OpenTidalFarm is an open-source software for simulating and optimising tidal turbine farms.The positioning of the turbines in a tidal farm is a crucial decision. Simulations show that the optimal positioning can increase the power generation of the farm by up to 50% and can therefore determine the viability of a project. However, finding the optimal layout is a difficult process due to the complex flow interactions. OpenTidalFarm solves this problem by applying an efficient optimisation algorithm onto a accurate flow prediction model.
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Journal articlePrelat A, Hogdson DM, Hall M, et al., 2015,
Constraining sub-seismic deep-water stratal elements with electrofacies analysis; a case study from the Upper Cretaceous of the Måløy Slope, offshore Norway
, Marine and Petroleum Geology, Vol: 59, Pages: 268-285Electrofacies represent rock facies based on wireline-log measurements and allow extrapolation of petrophysical characteristics away from levels that are calibrated to core. This approach has been employed to reduce uncertainty in the sub-seismic depositional elements of the late Cenomanian-Coniacian succession, northern Måløy Slope, offshore Norway. From core logging, eleven distinct sedimentary facies are grouped into four facies associations: FA A-turbidite sandstones, FA B-heterolithic siltstones and sandstones, FA C-debrites and FA D-slide and slump deposits. Each sedimentary facies association is characterised by a distinct combination of petrophysical characteristics, such as porosity, density, gamma-ray, sonic and resistivity. Using a neural network, calibration of electrofacies with sedimentary facies association allows their thickness and stacking pattern to be documented across the Upper Cretaceous stratigraphy. This approach is particularly useful where well log facies associations are poorly constrained due to the variable presence of glauconite, and sandstone units are challenging to distinguish from shale-rich units on a gamma-ray log. Results indicate that the succession of interest is dominated by debris flow, slide, and slump deposits, which are commonly poorly imaged on seismic reflection datasets in the northern North Sea. The methodology presented here represents a step forward in correlation at production and exploration scales of stratigraphic successions with similar burial histories, and in the identification of widespread mass flow deposits present in Upper Cretaceous deep-water systems of the North Sea.
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Conference paperJardine RJ, Merritt AS, Schroeder FC, 2015,
The ICP design method and application to a North Sea offshore wind farm
, Pages: 247-256, ISSN: 0895-0563This paper outlines the Imperial College Pile (ICP) approach for developing reliable predictions for the axial capacity of driven piles. The ICP's advantages over traditional design methods have led to widespread use in offshore oil and gas developments. The methods are now playing a critical role in major Northern European offshore wind projects. Hundreds of large steel tubular piles are being driven in the North and Baltic seas and improving design efficiency is crucial to the industry's economic success. This paper provides an overview of the development of the ICP design methods and summarizes their key features, together with experience-based guidance on their application. Their application is illustrated by reference to the North Sea Borkum West II wind farm, where 40 turbines have been installed on steel tripods founded on large diameter steel piles driven in very dense sands. The paper reports how the significant effects of axial and lateral cyclic loading were addressed for Borkum West II through the ICP design methodology.
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- Citations: 3
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Conference paperZwanenburg C, Jardine RJ, 2015,
The characterisation of operational shear strength for peats through full scale trials combined with laboratory and field testing
, Pages: 2455-2460Full scale, heavily-instrumented, field tests were conducted on peat to find operational foundation shear strength parameters for flood protection dikes that run through an area of outstanding beauty. The low submerged unit weights of peats usually lead to very low effective stresses, stiffness and uncertain undrained shear strengths. The loading tests, which were conducted both with and without preloading, provided guidance on these key questions. Shear failures were induced and even modest pre-loading was shown to generate both large vertical strains and significant bearing capacity improvements. The research also provided an opportunity to check and calibrate a range of laboratory and field characterisation techniques, leading to the broad set of conclusions summarised in the paper.
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Journal articlePatruno S, Hampson GJ, Jackson CA-L, et al., 2015,
Clinoform geometry, geomorphology, facies character and stratigraphic architecture of a sand-rich subaqueous delta: Jurassic Sognefjord Formation, offshore Norway
, Sedimentology, Vol: 62, Pages: 350-388The integration of core sedimentology, seismic stratigraphy and seismic geomorphology has enabled interpretation of a sand-prone subaqueous delta in the Upper Jurassic Sognefjord Formation of the Troll Field, Horda Platform, offshore Norway. Mud-prone subaqueous deltas characterised by a compound clinoform morphology are common in many modern tide- and wave-influenced settings, but ancient examples are rarely reported. The Sognefjord Formation data therefore demonstrate the criteria for recognition of subaqueous deltas in the stratigraphic record, as well as refining the depositional model of the main reservoir in the super-giant Troll oil and gas field. Two 10-60 m thick, wave-dominated, regressive-transgressive packages bounded by major marine flooding surfaces are distinguished in the lower Sognefjord Formation. Each regressive-transgressive package corresponds to a set of seismically resolved, westerly-dipping clinoforms, and its bounding surfaces form the seismic “envelope” of a clinoform set. The packages thicken westwards, until they reach a maximum where the clinoform “envelope” rolls over to define a topset-foreset-toeset geometry at the position of maximum regression. Both individual clinoforms and reflections bounding the clinoform sets are oriented sub-parallel to the edge of the Horda Platform (N005-N030). In the eastern half of the field, individual clinoforms are relatively gently dipping (1°-6°) and bound thin (10-30 m) clinothems dominated by fine-grained, hummocky cross-stratified sandstones. Towards the west, clinoforms gradually become steeper (5°-14°) and bound thicker (15-60 m) clinothems that comprise medium-grained, cross-bedded sandstones in their upper parts. Topsets are consistently well developed, except in the westernmost area, where some clinoform foresets are top-truncated. No evidence of subaerial exposure is observed. We interpret deposition by fully subaqueous, near-linear clinoforms that pro
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Conference paperJardine RJ, Thomsen NV, Mygind M, et al., 2015,
Axial capacity design practice for North European wind-turbine projects
, Pages: 581-586Improving foundation design is central to the offshore wind industry developing deeper water sites. This paper reviews the technical and regulatory difficulties for design of axially loaded piles to German offshore windfarm projects. It is argued that moving towards reliable forward predictive pile design methods and away from ‘dynamic proving tests’ will be vital to reducing unnecessarily high material and installation costs, installation risks and disturbance to marine mammals. Steps are outlined to implement such a change either in combination with regional or international load and resistance factors.
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Conference paperByrne BW, McAdam R, Burd HJ, et al., 2015,
New design methods for large diameter piles under lateral loading for offshore wind applications
, Pages: 705-710Offshore wind turbines are typically founded on single large diameter piles, termed monopiles. Pile diameters of between 5mand 6mare routinely used, with diameters of up to 10 m, or more, being considered for future designs. There are concerns that current design approaches, such as the p − y method, which were developed for piles with a relatively large length to diameter ratio, may not be appropriate for large diameter monopiles. A joint industry project, PISA (PIle Soil Analysis), has been established to develop new design methods for large diameter monopiles under lateral loading. The project involves three strands of work; (i) numerical modelling; (ii) development of a new design method; (iii) field testing. This paper describes the framework on which the new design method is based. Analyses conducted using the new design method are compared with methods used in current practice.
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Conference paperRimoy SP, Jardine RJ, 2015,
Analysis of an extended field test database regarding driven pile ageing in sands
, Pages: 1157-1162Field testing has revealed that the axial capacities of piles driven in sand can increase dramatically with age after driving. Jardine et al (2006) showed from experiments conducted in Dunkirk that the processes are affected by the history of prior loading and assembled a modest database of field cases to support the evidence from their single test site. This paper reports an extended database that is used to assess: The distinct contributions of base and shaft loads; the potential influence of loading sign (compression or tension); the effects of any prior failures; the influence of groundwater type as well as the effects of pile diameter and material. The analysis presented is informed by parallel highly instrumented model tests that were designed to explore the fundamental driving mechanisms. The findings have important implications for the re-assessment and re-use of foundations in a wide range of onshore and offshore project settings.
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Conference paperZdravković L, Taborda DMG, Potts DM, et al., 2015,
Numerical modelling of large diameter piles under lateral loading for offshore wind applications
, Pages: 759-764There is currently a significant focus on developing offshore wind power in the UK and Europe. The most common foundation type for wind turbines is a single large diameter pile, termed a monopile, on which the turbine is located. As the diameter of such piles is envisaged to increase in future installations, there are concerns that current design methods are not applicable. To explore this problem, the joint industry project PISA has been established, with the aim to develop a new design framework for laterally loaded piles utilised in the offshore wind industry, based on new theoretical developments, numerical modelling and large scale field pile testing. This paper presents an overview of numerical modelling undertaken as part of the project.
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Conference paperRimoy SP, Jardine RJ, 2015,
Axial capacity ageing trends of piles driven in silica sands
, Pages: 637-642Field studies of piles driven in silica sands have shown axial capacity increases (set-up) over the days to months that follow driving, long after installation induced pore pressures have dissipated. Three main hypotheses have been proposed regarding the governing mechanisms and tested to a limited extent through relatively modest databases of pile load tests. However, a secure understanding of the governing mechanisms is required before projecting ageing predictions for other cases and considering how ageing trends might be affected by, for example, scale, pile type, groundwater regime or submerged offshore conditions. This paper reports an extended database study aimed at assessing the distinct ageing contributions of base and shaft loads, the potential influence of compression or tension axial loading directions, the effects of prior loading history, the influence of groundwater type as well as the effects of pile diameter and material. The analysis is informed by parallel highly instrumented model tests that were designed to investigate and identify the fundamental ageing mechanisms. The findings have important implications for pile design and re-assessment.
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Journal articleMiljkovic K, Wieczorek MA, Collins GS, et al., 2015,
Excavation of the lunar mantle by basin-forming impact events on the Moon
, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 409, Pages: 243-251, ISSN: 0012-821X- Author Web Link
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- Citations: 62
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Journal articleStafford PJ, 2015,
Variability and uncertainty in empirical ground-motion prediction for probabilistic hazard and risk analyses
, Geotechnical, Geological and Earthquake Engineering, Vol: 39, Pages: 97-128, ISSN: 1573-6059© The Author(s) 2015. The terms aleatory variability and epistemic uncertainty mean different things to people who routinely use them within the fields of seismic hazard and risk analysis. This state is not helped by the repetition of loosely framed generic definitions that actually inaccurate. The present paper takes a closer look at the components of total uncertainty that contribute to ground-motion modelling in hazard and risk applications. The sources and nature of uncertainty are discussed and it is shown that the common approach to deciding what should be included within hazard and risk integrals and what should be pushed into logic tree formulations warrants reconsideration. In addition, it is shown that current approaches to the generation of random fields of ground motions for spatial risk analyses are incorrect and a more appropriate framework is presented.
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Journal articleJacobs CT, Avdis A, Mouradian SL, et al., 2015,
Integrating research data management into geographical information systems
, CEUR Workshop Proceedings, Vol: 1529, Pages: 7-17, ISSN: 1613-0073Ocean modelling requires the production of high-fidelity com-putational meshes upon which to solve the equations of motion. The production of such meshes by hand is often infeasible, considering the complexity of the bathymetry and coastlines. The use of Geographical Information Systems (GIS) is therefore a key component to discretising the region of interest and producing a mesh appropriate to resolve the dynamics. However, all data abociated with the production of a mesh must be provided in order to contribute to the overall recomputability of the subsequent simulation. This work presents the integration of re-search data management in QMesh, a tool for generating meshes using GIS. The tool uses the PyRDM library to provide a quick and easy way for scientists to publish meshes, and all data required to regenerate them, to persistent online repositories. These repositories are abigned unique identifiers to enable proper citation of the meshes in journal articles.
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Journal articleJacobs CT, Goldin TJ, Collins GS, et al., 2015,
An improved quantitative measure of the tendency for volcanic ash plumes to form in water: implications for the deposition of marine ash beds
, JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, Vol: 290, Pages: 114-124, ISSN: 0377-0273- Author Web Link
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- Citations: 9
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