Guy Tinmouth Houlsby

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• MA, DSc
• Professor Emeritus at University of Oxford

Clays exhibit complex mechanical behaviour with significant viscous, nonlinear, and hysteric characteristics, beyond the prediction capacity of the well-known modified cam clay (MCC) model. This paper extends the MCC model to address these important limitations. The proposed family of models is constructed entirely within the hyperplasticity framew...

Offshore wind has a key role to play in the energy transition. The majority of offshore wind turbines (OWTs) are bottom-founded with monopiles [1]. Monopiles account for up to 35% of the installation cost of the OWT [2, 3]. Optimising the design of monopiles can thus lead to significant savings and increased competitiveness of OWTs in the energy ma...

This paper explores the application of a numerical method for modeling pseudorandom cyclic loading, at very large cycle numbers , to the design of offshore wind turbine foundations. The work expands the development of a novel constitutive modeling framework, the hyper-plastic accelerated ratcheting model (HARM), for which the key constitutive equat...

Jacket structures are used to support offshore facilities, such as those to support oil and gas reservoir facilities and for renewable energy to support substations and wind turbine generators. Most jackets are connected to the seabed using open-ended steel tubular piles. The design methods for the capacity of these open-ended piles were calibrated...

This paper presents a theoretical framework termed the convex modular modelling (CMM) framework, which provides a convenient and expedient approach for constructing thermodynamically consistent constitutive models. This paper demonstrates how the CMM framework can be used to build increasingly complex constitutive models by mixing and matching re-u...

Monopile foundations supporting offshore wind turbines are exposed to cyclic lateral loading, which can cause accumulated pile displacement or rotation and evolution of the dynamic response. To inform the development of improved design methods, the monopile's response to cyclic lateral loading has been explored through small-scale physical modeling...

A simple model is presented in which the hyperplasticity approach is used to develop a model at the micro-scale, with energy and dissipation terms then being integrated over a Representative Volume Element to deduce the macroscopic response. Strong kinetic or kinematic assumptions do not need to be made, as the perturbations from affine deformation...

The PISA design model is a procedure for the analysis of monopile foundations for offshore wind turbine applications. This design model has been previously calibrated for homogeneous soils; this paper extends the modelling approach to the analysis of monopiles installed at sites where the soil profile is layered. The paper describes a computational...

Robust design of offshore wind turbine foundations requires that the ultimate capacity is acceptable. In addition the accumulated deformations over 25 years of operational life, typically 10 8 cycles, must also be limited. This paper outlines a numerical method for modelling the response of monopiles to monotonic and cyclic lateral loading to very...

This paper describes a one-dimensional (1D) computational model for the analysis and design of laterally loaded monopile foundations for offshore wind turbine applications. The model represents the monopile as an embedded beam and specially formulated functions, referred to as soil reaction curves, are employed to represent the various components o...

Offshore wind turbines in shallow coastal waters are typically supported on monopile foundations. Although three-dimensional (3D) finite-element methods are available for the design of monopiles in this context, much of the routine design work is currently conducted using simplified one-dimensional (1D) models based on the p–y method. The p–y metho...

In this paper, the nonlinear anisotropic hyperelastic model recently proposed by Houlsby et al. (2019) is critically analysed and validated against experimental data. The model, here mainly discussed in terms of its strain energy function, is initially compared to existing formulations for the cases of nonlinear isotropic, linear anisotropic and th...

Located in between the Flores and Adonara islands, Larantuka strait has one of the strongest tidal currents in Indonesia. An 810 m length bridge is planned to be constructed across the strait to connect the islands. Commencing in 2019, the Palmerah Bridge Project is planned to be the first combined tidal energy/bridge project worldwide. By combinin...

This paper is the first of a set of linked publications on the PISA Joint Industry Research Project, which was concerned with the development of improved design methods for monopile foundations in offshore wind applications. PISA involved large-scale pile tests in overconsolidated glacial till at Cowden, north-east England, and in dense, normally c...

The PISA Joint Industry Research Project was concerned with the development of improved design methods for monopile foundations in offshore wind applications. PISA involved large-scale pile tests in overconsolidated glacial till at Cowden, north-east England, and in dense, normally consolidated marine sand at Dunkirk, northern France. This paper de...

This paper describes the results obtained from a field testing campaign on laterally loaded monopiles conducted at Cowden, UK, where the soil consists principally of a heavily overconsolidated glacial till. These tests formed part of the PISA project on the development of improved design methods for monopile foundations for offshore wind turbines....

The results obtained from a field testing campaign on laterally loaded monopiles, conducted at a dense sand site in Dunkirk, northern France are described. These tests formed part of the PISA project on the development of improved design methods for monopile foundations for offshore wind turbines. Results obtained from monotonic loading tests on pi...

The PISA project was a combined field testing/numerical modelling study with the aim of developing improved design procedures for large-diameter piles subjected to lateral loading. This paper describes the development of a three-dimensional finite-element model for the medium-scale pile tests that were conducted in Cowden till as part of the PISA w...

The paper presents the development of a three-dimensional finite-element model for pile tests in dense Dunkirk sand, conducted as part of the PISA project. The project was aimed at developing improved design methods for laterally loaded piles, as used in offshore wind turbine foundations. The importance of the consistent and integrated interpretati...

Monopiles supporting offshore wind turbines experience combined moment and horizontal loading which is both cyclic and complex – continuously varying in amplitude, direction and frequency. The accumulation of rotation with cyclic loading (ratcheting) is a key concern for monopile designers and has been explored in previous experimental studies, whe...

A very simple frictional plasticity model for a granular material is presented, including the effects of dilation. The novelty lies in the fact that this is described within the hyperplasticity framework, expressed using the terminology of convex analysis. This allows a consistent mathematical treatment of the dilation constraint. The Fenchel Dual...

Bali Island and Lombok Island are amongst the most famous tourist locations in Indonesia. The straits in this area have high velocity tidal streams and are already being considered by major turbine manufacturers as potential sites for tidal stream turbines. Three islands (Nusa Penida, Nusa Lembongan and Nusa Ceningan) separate the Lombok straits in...

This paper provides a summary of the PIle Soil Analysis (PISA) project, completed in the UK during the period 2013 to 2018. The research led to the development of a new, computationally efficient, one dimensional design model for laterally loaded monopile foundations, particularly for offshore wind turbine support structures. The current form of th...

We describe a non-linear anisotropic hyperelastic model appropriate for geomaterials, deriving the full stress-strain response from strain energy or complementary energy functions. Specific forms of the functions are chosen so that the stiffness and compliance matrices have the appropriate minor symmetries. The model employs two material parameters...

There are two approaches to extracting power from tides — either turbines are placed in areas of strong flows or turbines are placed in barrages enabling the two sides of the barrage to be closed off and a head to build up across the barrage. Both of these energy extraction approaches will have a significant back effect on the flow, and it is vital...

An array of ten 1 MW turbines, with a one diameter inter-turbine spacing, is simulated in a hypothetical tidal channel using the depth-averaged flow solver TELEMAC-2D. It has been shown for idealised turbines that mean power extraction from tidal channels can be enhanced by tuning turbine resistance for a given channel. Blade element momentum theor...

This paper provides an overview of the PISA design model recently developed for laterally loaded offshore wind turbine monopiles through a major European joint-industry academic research project, the PISA Project. The focus was on large diameter, relatively rigid piles, with low length to diameter (L/D) ratios, embedded in clay soils of different s...

This paper presents an analytical methodology for calibration of the Hyperplastic Accelerated Ratcheting Model (HARM, Houlsby et al., 2017 [3]), based on a closed-form expression for the accumulation of ratcheting strain with cyclic history. The proposed method requires the fit of one test response and of a few continuous cyclic tests. The initial...

Proceedings of the 7th Oxford Tidal Energy Workshop 8 - 9 April 2019, Oxford, UK Workshop Organisers: Richard H. J. Willden (Chairman) University of Oxford Christopher R. Vogel (Co-Chairman) University of Oxford Scientific Committee Members: T. A. A. Adcock (University of Oxford) J. Thake (SIMEC Atlantis Energy) G. T. Houlsby (University of Oxford)...

This paper provides a brief overview of the Pile Soil Analysis (PISA) project, recently completed in the UK. The research was aimed at developing new design methods for laterally loaded monopile foundations, such as those supporting offshore wind turbine structures. The paper first describes the background to the project and briefly outlines the ke...

This paper presents experimental work aimed at improving understanding of the behaviour of rigid monopiles, in cohesionless soils, subjected to lateral cyclic loading. It involves 1g laboratory model tests, scaled to represent monopile foundations for offshore wind turbines. The test programme is designed to identify the key mechanisms governing pi...

A key hydrodynamic difference between tidal current and wind turbines is the volume-flux constrained flow field in which tidal turbines operate and the resulting streamwise static pressure difference that develops in the flow passage. Blade Element Momentum (BEM) theory is extended to account analytically for the effects of blockage and the develop...

For a material or structural model, which satisfies the extended Masing rules under cyclic loading, a unique parallel or series Iwan-model exists which characterises the stress-strain response. Both the parallel and series version of the model result in the same stress-strain response when loaded in one dimension. In numerical implementation, the s...

In the offshore industry, open-ended steel piles are primarily designed using one of three pile design methods: the API (2011), the ICP (2005) and the UWA (2005). The soil plug, inside the pile, is considered differently in each of the methods, producing different pile lengths due to the varying assumptions adopted. A one-dimensional finite element...

Deep excavations are widely used for the development of underground space. The structural performance of any deep excavation is influenced by details of the soil behaviour, the form of the retaining and support structures that are employed and also the sequence of construction. Finite element analysis is potentially an effective tool for considerin...

This paper describes the aspects of power capping strategies in asymmetric tidal patterns. The capping strategies that are widely used in UK and Canada, where the tides are mostly semidiurnal and M2 is the dominant component driving the tidal current, might not be applicable in an area with pronounced diurnal components resulting in tidal asymmetry...

In this note a new hyperelastic model is proposed to reproduce the nonlinear anisotropic reversible response of a wide class of geomaterials. The research is motivated by the non-negligible role played by stress-dependent and anisotropic elasticity, as combined with plasticity, in the modelling of the mechanical behaviour of soils and soft rocks un...

Excavations for deep basements in urban areas present complex design questions, e.g. related to the selection of retaining systems and the specification of construction processes. Consideration must be given to the design of structural systems to support the excavation and the mitigation of any impact that the construction might have on any nearby...

This paper describes the outcome of a recently-completed research project – known as PISA – on the development of a new process for the design of monopile foundations for offshore wind turbine support structures. The PISA research was concerned with the use of field testing and three-dimensional (3D) finite element analysis to develop and calibrate...

In the PISA project, over 28 pile test are performed to investigate the behaviour of monopile foundations. These test piles are instrumented with inclinometers and displacement transducers above ground; a subset of the piles are instrumented below ground with inclinometers, extensometers and strain gauges. To analyse the data, processing tools are...

Current design standards for offshore open-ended piles vary in their consideration of the soil plug’s contribution to the pile’s axial capacity and, indirectly, to its stiffness. API RP2 GEO (2011) and UWA-05 (Lehane et al., 2005) consider the contribution of the plug, but ICP-05 (Jardine et al., 2005) combines the plug capacity with the end bearin...

Improved design of laterally loaded monopiles is central to the development of current and future generation offshore wind farms. Previously established design methods have demonstrable shortcomings requiring new ideas and approaches to be developed, specific for the offshore wind turbine sector. The Pile Soil Analysis (PISA) Project, established i...

This paper outlines experimental and theoretical research exploring the response of rigid piles to cyclic lateral loading, relevant to large diameter monopiles for offshore wind applications. The experimental work comprised of 1-g laboratory scale model tests in sand, where up to 100,000 cycles were applied. The tests were designed specifically for...

as a country with emerging economic growth, Indonesia is facing challenges associated with energy security for its future. Currently, Indonesia still relies on fossil fuels as its energy main sources. However, Indonesian oil and gas productivities have been declining in recent years and Indonesia has become a net importer of oil and gas. These cond...

The power available to a tidal stream turbine fence depends on the turbine resistance, the mass flux through the array, as well as the flow speed variation within the array. Depth-averaged simulations are often used to analyse the power available at a site, where the array is modelled as a region of enhanced flow resistance. Without special treatme...

Osterberg Lecture at Northwestern University, USA

We present a theoretical model to describe the response of a one dimensional mechanical system under cyclic loading. Specifically, the model addresses the non-linear response on loading, hysteretic behaviour on unloading and reloading, and the phenomenon of ratcheting under very many cycles. The methods developed are formulated within the hyperplas...

This paper presents data from a case history of tunnelling using the pre-vaulting method, at low cover and without compensation grouting, beneath a terrace of masonry buildings at Ramsgate, Kent. Surface and building settlements were measured and movements on existing cracks monitored throughout construction. Volume loss was low and the settlement...

Development of improved methods to capture the lateral cyclic behaviour of offshore wind monopiles through experimental and theoretical modelling

This paper presents a numerical investigation of ducted tidal turbines, employing three-dimensional Reynolds-averaged Navier-Stokes simulations. Bidirectional ducted turbines are modelled with and without apertures, referred to as ducted and open-centre turbines respectively. The turbine rotors are represented through a CFD-integrated blade element...

This paper presents some examples of design problems for offshore foundations, drawn from the jack-up industry and the wind turbine industry. The examples are chosen to illustrate some general points about foundation design, geotechnical engineering and its interaction with other disciplines. The first example is drawn from the assessment of the sa...

An analytic actuator disc model which includes the deformation of the free surface and the wake mixing downstream of the turbine to estimate more precisely the power available to a tidal turbine. In particular the potential environmental and structural benefits of operating tidal turbines at points other than the peak power coefficient were explore...

The effect of free surface deformation on the power extracted by a tidal turbine array partially spanning a wide channel is investigated using a theoretical model. Two predominant flow scales are assumed; turbine-scale flow, and array-scale flow, which are analysed as quasi-inviscid open channel flow problems in which conservation of mass, momentum...

The design of deep excavations requires careful consideration of the influence of various soil/structure interaction mechanisms and detailed issues relating to the construction processes and the mechanics of the soil. Finite-element analysis provides a useful design tool for deep excavations, but care needs to be taken to ensure that an appropriate...

The design of deep excavations requires careful consideration of the influence of various soil/structure interaction mechanisms and detailed issues relating to the construction processes and the mechanics of the soil. Finite-element analysis provides a useful design tool for deep excavations, but care needs to be taken to ensure that an appropriate...

Blockage-corrected blade element momentum theory is employed to investigate the performance of tidal turbine arrays in a head-driven oscillating tidal channel. Two arrays are compared, one with power capping, and one without. Power capping is widely used in the wind turbine industry as a means of finding an economic balance between the power (and h...

In recent years, fibre Bragg grating (FBG) sensors have emerged as a relatively new strain sensing technology for civil engineering applications. This paper presents a field trial to assess the feasibility of using FBG sensor arrays to measure strain in driven steel piles. Two FBG arrays were installed in grooves within the wall of an open-ended st...

Offshore wind turbines are typically founded on single large diameter piles, termed monopiles. Pile diameters of between 5m and 6m are routinely used, with diameters of up to 10m, 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...

There 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 m...

The renewable tidal current resource has attracted significant global interest as a predictable energy resource. Although the understanding of the tidal current resource has advanced considerably by transferring knowledge from the wind energy industry, a number of important differences exist between wind and tidal current turbines. Chief among thes...

One of the important pre-processing stages in the analysis of jointed rock masses is the identification of rock blocks from discontinuities in the field. In 3D, the identification of polyhedral blocks usually involve tedious housekeeping algorithms, because one needs to establish their vertices, edges and faces, together with a hierarchical data st...

This paper presents a numerical investigation of the behaviour of dry granular flows generated by the collapse of prismatic columns via 3D Discrete Element Method (DEM) simulations in plane strain conditions. Firstly, by means of dimensional analysis, the governing parameters of the problem are identified, and variables are clustered into dimension...

A systematic approach of using the distinct element method (DEM) to provide useful insights for tunnel support in moderately jointed rock masses is illustrated. This is preceded by a systematic study of common failure patterns for unsupported openings in a rock mass intersected by three independent sets of joints. The results of our simulations sho...

Offshore wind turbines play a key part in the renewable energy strategy in the UK and Europe as well as in other parts of the world (for example, China). The majority of current developments, certainly in UK waters, have taken place in relatively shallow water and close to shore. This limits the scale of the engineering to relatively simple structu...

This paper compares analyses performed via the distinct element method (DEM), employing rigid blocks and compliant joints, with results using finite-difference software (FLAC) obtained previously by other researchers. The paper then examines the capability of the rigid-block DEM at modelling joints realistically, with emphasis on the moment transfe...

The Pentland Firth, Scotland, is one of the World's prime locations for the eventual installation of large farms of tidal stream turbines. This paper seeks to improve the upper bound estimate of available power output obtained by Adcock etal. (2013) who used a depth-integrated numerical model of the region containing the Pentland Firth with the out...

This paper presents three dimensional numerical investigations of batch sedimentation of spherical particles in water, by analyses performed by the discrete element method (DEM) coupled with computational fluid dynamics (CFD). By employing this model, the features of both mechanical and hydraulic behaviour of the fluid-solid mixture system are capt...

A water turbine is disclosed comprising a rotor mounted to be rotatable about an axis. The rotor comprises at least three blades for causing the rotor to rotate about the axis when the blades are located in flowing water. The rotor comprises a plurality of members in the form of a triangulated structure, and at least one of said members comprises o...

The 1963 Vajont rock slide is studied using the distinct-element method (DEM). Two-dimensional (2D) and three-dimensional (3D) DEM models were constructed based on information published in the literature. In this study, a strength reduction approach was used to calculate the slide surface friction angles required for stability. The influence of sev...

A simple numerical model of granular column collapse has been employed in this research to investigate the mobilization mechanisms of submerged debris flows. The motion of solid grains is calculated by the Discrete Element Method (DEM) and the fluid flow is simulated by the Computational Fluid Dynamics (CFD). The interaction between fluid and solid...

In 1695, in his Opera Mathematica, John Wallis (Savilian Professor of Geometry at the University of Oxford) published an analysis of the forces in a reciprocal grillage structure. The structure itself was an extended version of a famous design often attributed to Serlio, but first sketched much earlier by Villard de Honnecourt. The extended structu...

Copies of slides presented at the Rankine Lecture 2014, and the slides with notes of the spoken version. The lecture can be viewed online at https://ice.org.uk/eventarchive/54th-bga-rankine-lecture-interactions-christchurch (although misleadingly the website refers to the version delivered in Christchurch, New Zealand, rather than the original lect...

The Pentland Firth is arguably the best-known candidate site for tidal stream power extraction worldwide. In this paper we estimate the maximum power that can be extracted by placing tidal stream power devices across the Pentland Firth and/or the individual sub-channels formed by the islands of Swona, Stroma and the Pentland Skerries. Using a depth...

The construction of the North Square Shopping Center of the Shanghai South Railway Station is a large scale complex top-down deep excavation project. The excavation is adjacent to several current and newly planned Metro lines, and influenced by a neighboring Exchange Station excavation. The highly irregular geometry of this excavation greatly incre...

Several locations in the Pentland Firth, UK, have been earmarked for the deployment of separate farms of tidal turbines. However recent numerical modelling suggests that these farms will be inter-dependent and that they must work together to optimiz their collective performance. To explain this inter-dependence, in this paper we develop an electric...

This chapter is about the role of the dissipation rate function—and other functions derived from it—in determining the constitutive behaviour of dissipative materials. It consists of a discussion of some general theory, followed by examples. We address the class of materials for which knowledge of the functional form of the dissipation rate functio...

This paper is the third of three, which describe the procedures and results for a set of experiments on various configurations of the Transverse Horizontal Axis Water Turbine (THAWT), which is a horizontally orientated variant of the Darrieus cross-flow turbine. Tests were conducted in the combined wind, wave and current tank at Newcastle Universit...

This paper is the second of three, which outline the procedures and results for a set of experiments on various configurations of the Transverse Horizontal Axis Water Turbine (THAWT), which is a horizontally orientated variant of the Darrieus cross-flow turbine. Tests were conducted in the combined wind, wave and current tank at Newcastle Universit...

This paper is the first of three, which outline the procedures and results for a set of experiments carried out on various configurations of the Transverse Horizontal Axis Water Turbine (THAWT), which is a horizontally orientated variant of the Darrieus cross-flow turbine. Tests were conducted in the combined wind, wave and current tank at Newcastl...

An approach is described, based on Bayesian statistical methods, that allows the fitting of a design profile to a set of measurements of undrained strengths. In particular allowance is made for the automatic determination of not only the positions of boundaries between geological units, but also the selection of the number of units to model the dat...

A new contact detection algorithm between three-dimensional non-spherical particles in the discrete element method (DEM) is proposed. Houlsby previously proposed the concept of potential particles where an arbitrarily shaped convex particle can be defined using a 2nd degree polynomial function (Houlsby [1]). The equations in 2-D have been presented...