David Potts

David Potts
Imperial College London | Imperial · Department of Civil and Environmental Engineering

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337
Publications
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Introduction
Skills and Expertise

Publications

Publications (337)
Conference Paper
Full-text available
The expansion of offshore wind energy to new markets around the world, in the process of decarbonising the global energy sector, necessitates that new wind farm sites move further away from the current near-shore sites and hence into deeper waters. As a consequence, the existing foundation systems of monopiles and jacket structures, which are well...
Article
In the emerging field of energy geotechnics, many applications involve changes of temperature above and below ambient temperature. This has led to the development of laboratory apparatus to enable the study of soil behavior under various temperature ranges and under well-controlled conditions. To understand the effect of temperature on soil behavio...
Conference Paper
Full-text available
The influence of dynamic Soil-Structure-Interaction (SSI) phenomena on the response of structures under dynamic loading is widely recognised. These phenomena are more impactful on structures that are founded on soft soil sites, where soil nonlinearity can prevail. The present study examines this aspect by the means of three-dimensional nonlinear fi...
Preprint
Predictive estimation, which comprises model calibration, model prediction, and validation, is a common objective when performing inverse uncertainty quantification (UQ) in diverse scientific applications. These techniques typically require thousands to millions of realisations of the forward model, leading to high computational costs. Surrogate mo...
Article
Full-text available
Recent developments have demonstrated that the behaviour of segmental grey cast iron (GCI) tunnel linings can be simulated accurately with sophisticated 3D numerical models where the geometry of the segments and joints is considered explicitly. Such a 3D model is, however, impractical for geotechnical numerical analyses where the tunnel lining is u...
Article
In the finite element (FE) modelling of transient coupled problems for soils, the associated equations need to be integrated numerically over a time interval during the solution process. A minimum time-step size has been observed to exist, below which spatial oscillations in the obtained solutions can occur. These oscillations might lead to an accu...
Article
Full-text available
The present-day condition of a grey cast iron (GCI) tunnel was investigated numerically by means of a series of plane-strain geotechnical analyses that focused on establishing the influence of the modelling approach adopted to simulate the behaviour of longitudinal tunnel joints. The GCI tunnel lining was simulated in three different ways: (i) as a...
Article
The thermal behaviour of KSS, a low plasticity artificial clay made with kaolin clay, silt, and sand, was investigated in a series of temperature-controlled oedometer tests, at temperatures between 5 °C and 70 °C, and at vertical pressures up to 2.4 MPa. The experiments investigated the effect of over-consolidation ratio (OCR), pressure level, and...
Conference Paper
Floating offshore wind turbines are the subject of increasing interest, as a response to growing societal demands for renewable energy. They enable the harnessing of wind power further away from the coast in larger and deeper offshore fields where fixed structures may not be practical, which in turn imposes challenges for their mooring systems. Thi...
Conference Paper
Advanced constitutive models, such as those formulated in the bounding surface plasticity framework, enable a reliable representation of sand behaviour and have been shown successful in predicting the response of monopiles subjected to monotonic lateral loading. They, however, have a large number of input parameters which may require a lengthy cali...
Conference Paper
Full-text available
Offshore wind turbines in the North Sea are designed to ensure that fundamental frequencies of the turbine-substructure systems lie outside frequency ranges occupied by dynamic wind loads, wave loads and rotor and blade-passing frequencies. For wind farms located in areas of high seismicity, dynamic earthquake loading needs to be further considered...
Conference Paper
Full-text available
The accurate simulation of the present-day deformations and internal forces of existing tunnels is essential when predicting the available capacity of such tunnels to sustain further loading from new construction in their vicinity. In this paper, the present-day condition of a single tunnel located in the London Clay formation is simulated with a s...
Article
Full-text available
The structural assessment of segmental grey cast iron (GCI) tunnel linings to nearby construction is challenging due to the presence of the joints affecting the stiffness of the tunnel lining. This paper presents an extensive investigation, using 3D finite element (FE) analyses, into the bending moment-rotation (M-θ) behaviour of two GCI tunnel joi...
Conference Paper
Full-text available
Soil-Structure Interaction (SSI) phenomena and foundation rocking can modify the structural response significantly with respect to the response predicted adopting the fixed-base assumption. The importance of SSI and rocking depends, among other factors, on the structural mass and the distribution of static stresses at the soil-foundation interface....
Conference Paper
Full-text available
An increasing number of offshore energy structures have been built recently on driven piles, ranging from jacket piles with typical length-to-diameter (L/D) ratios of 10-40 to monopiles with far lower L/D ratios. The load-displacement behaviour of these foundations can be investigated by means of Finite Element (FE) analyses, for instance following...
Conference Paper
Full-text available
Engineered barriers employed in geological radioactive waste repositories are usually formed of compacted unsaturated bentonite blocks, often used together with bentonite pellets. Compacted bentonite blocks have very low permeabilities, hence their saturation can take hundreds of years. Predicting the bentonite behaviour over such a long time frame...
Article
Full-text available
High-quality rotary core samples of natural London Clay were taken during installation of subsurface instrumentation to monitor the ground response at Hyde Park, London, to the construction of Crossrail tunnels. An extensive programme of advanced triaxial tests was performed on specimens from London Clay divisions A3 to C. Detailed analysis of thei...
Article
Full-text available
MX-80 bentonite has been considered as a suitable material for the construction of engineered barriers employed in deep geological radioactive waste repositories. These barriers are generally formed of compacted unsaturated bentonite, the latter experiencing a slow saturation due to its low permeability whileinteracting with the surrounding groundw...
Conference Paper
Full-text available
Advanced constitutive models that are capable of reproducing different aspects of sand behaviour have been an object of study for many years. The models developed in the critical state soil mechanics framework, with a formulation based on the state parameter, are of particular interest as they can predict the sand response over a full range of stre...
Conference Paper
Full-text available
Dynamic Soil-Structure-Interaction (DSSI) phenomena can considerably affect the structural response under dynamic loading. Time domain finite element analysis allows to study these phenomena in depth, but several computational challenges need to be addressed first to achieve rigorous modelling of both the structure and soil domain. Within this cont...
Article
In this paper, 2-dimensional, hydro-mechanically coupled finite element analyses are conducted to assess the performance of an engineered barrier, constructed from natural geomaterials, aimed at reducing flood risk in urban environments. The barrier consists of an unsaturated compacted soil layer with water holding properties and a drainage layer o...
Conference Paper
Full-text available
Field experiments were conducted with EUROPROTEAS, a real-scale prototype structure at the Eutoseistest experimental facility located in the Mygdonian Valley in Northern Greece, to study the impact of Dynamic Soil-Structure-Interaction (DSSI) effects on the structural and soil response. The experiments consisted of a steel frame structure founded o...
Conference Paper
Full-text available
CACTUS (Climate Adaptation Control Technologies for Urban Spaces) is an ongoing research project that is investigating the development of “climate adaptation composite barrier systems” capable of limiting the impact of a changing environment on buried geo-infrastructure, such as retaining walls and foundations. The project partners are investigatin...
Technical Report
Full-text available
Task 9 of SKB’s Engineered Barrier System Task Force (EBS TF) is devoted to the numerical analysis of the FEBEX in situ experiment, a full‐scale heating test performed at the Grimsel Test Site (GTS) in Switzerland. The Task goals are the enhancement of the understanding of the EBS THM behaviour during the transient phase, the detailed examination o...
Article
Scott Sloan (1954–2019) was a leader of academic engineering in Australia and beyond, as evidenced by his numerous professional accolades and important research achievements, which have had significant impact on his chosen profession of geotechnical engineering. Educated in Australia and the United Kingdom, he returned to Australia in 1984 and deve...
Article
Full-text available
The structural response of a segmental grey cast iron (GCI) tunnel lining ring under distortion was investigated by means of finite element (FE) analysis. Building on previous experimental investigations, a 3D numerical model, capable of reproducing accurately the behaviour observed in the laboratory, was developed with the aim of providing guideli...
Article
This paper presents a coupled thermo-hydro-mechanical (THM) finite element (FE) formulation which is capable of accounting for the effects of temperature change on the behaviour of unsaturated soils. Both vapour flow and density variation are taken into account in the development of this formulation. The full derivation procedure is provided and th...
Article
Thermo-active structures exchange heat with the ground to provide thermal energy to buildings. Consequently, the ground is subjected to changes in temperature, inducing thermo-hydro-mechanical (THM) interactions within the soil. To provide insights into the origin and manifestations of the main mechanisms taking place in complex fully THM-coupled f...
Conference Paper
Full-text available
The application of the finite element method to tunnelling problems in London Clay has received significant attention over decades of research, but has proved to be a challenging problem. Numerical predictions usually produce a surface settlement trough wider and shallower than field observations. Given the low permeability of the London Clay strat...
Conference Paper
Full-text available
In this paper, 2-dimensional, hydro-mechanically coupled finite element analyses are performed to assess the performance of an engineered barrier aimed at reducing flood risk in urban environments. The barrier consists of an unsaturated compacted soil layer and a drainage layer of a coarse granular material, constructed on top of the natural soil,...
Conference Paper
Thermo-active piles, as one form of ground source energy systems (GSES), utilise heat energy stored in the ground to provide low-carbon space heating and cooling, in addition to their primary function of providing structural stability as building foundations. This relatively new technology for generating renewable energy creates challenges for geot...
Conference Paper
Full-text available
CACTUS (Climate Adaptation Control Technologies for Urban Spaces) is an ongoing research project that is investigating the development of "climate adaptation composite barrier systems" capable of limiting the impact of a changing environment on buried geo-infrastructure, such as retaining walls and foundations. The project partners are investigatin...
Conference Paper
Recent studies have demonstrated the significance of the vertical seismic acceleration component for offshore wind turbines, as their low natural period in this direction can result in significant excitation, potentially making this load case design-driving. Unexpectedly high vertical ground accelerations, well exceeding their horizontal counterpar...
Conference Paper
Full-text available
Soil susceptibility to liquefaction is most commonly assessed in engineering practice using empirical correlations of in-situ tests with observed surface manifestations of liquefaction in case histories. This simplified design method further incorporates a correction factor for varying overburden pressure, derived from laboratory data, and provides...
Article
Full-text available
A new temperature-controlled oedometer has been designed at Imperial College London and commissioned to investigate the thermo-hydro-mechanical behaviour of soils. Under oedometric conditions, temperature can be varied between 5°C and 70°C, by submerging the specimen in a temperature-controlled water bath. This temperature range is appropriate for...
Article
Full-text available
The stabilisation of slopes with rows of discrete vertical piles is a commonly adopted method for both cuttings and embankment slopes. The majority of existing design procedures consider the pile only as an additional force or moment acting on the critical slip surface of the unstabilised slope. Based on simplified models, existing design methodolo...
Article
Full-text available
Buffer materials for nuclear waste disposal applications generally consist of blocks made of highly expansive compacted clay. However, high-density pellets of bentonite are being evaluated as an alternative buffer material for waste isolation. The material response of pellet-based buffers may be quite different from that of compacted buffers, becau...
Article
Thermo-active piles are capable of providing both structural stability as foundations and low carbon heating and cooling as ground source heat exchangers. When subjected to heating or cooling, the soil surrounding the pile restricts its expansion or contraction, giving rise to thermally-induced axial stresses, which need to be considered during des...
Article
Full-text available
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...
Conference Paper
The PISA Joint Industry Project has led to significant advances in monopile design, with 3D Finite Element (FE) analysis playing a key role in the development of the method, as well as in its application in practice. This paper presents 3D FE analyses carried out as part of the design process for monopile foundations for an offshore wind farm in th...
Article
Contemporary geotechnical design often requires the use of advanced numerical analysis, if it is to take account of the complex nature of many geotechnical problems. One crucial aspect of such analyses is the realistic representation of the facets of soil behaviour that are dominant in any given problem, which in turn requires a careful selection o...
Article
Full-text available
Conventional laboratory triaxial tests apply axisymmetric boundary conditions to a cylindrical sample which has an axisymmetric geometry. For a homogeneous sample this implies that the deformed shape of the sample should maintain an axisymmetric geometry during the test. Consequently, the sample should deform in a barrelling mode and if slip planes...
Article
Full-text available
Thermo-active structures are underground facilities that enable the exchange of thermal energy between the ground and the overlying buildings, thus providing renewable means of space heating and cooling. Although this technology is becoming increasingly popular, the behaviour of geotechnical structures under additional thermal loading is still not...
Data
This is a summary animation of the evolution of the thermal field and ground movements associated to energy extraction in a thermo-active tunnel.
Article
Ground source energy systems (GSES) utilize low enthalpy geothermal energy and have been recognized as an efficient means of providing low carbon space heating and cooling. This study focuses on GSES where the exchange of heat between the ground and the building is achieved by circulating a fluid through heat exchanger pipes. Although numerical ana...
Article
Thermo-active retaining walls are geotechnical structures employed as heat exchangers to provide low carbon dioxide heating and cooling to buildings. To assess the thermo-mechanical response of such structures, finite-element (FE) analyses are typically carried out. Due to the presence of heat exchanger pipes, the temperature distribution along the...
Article
Full-text available
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...
Article
Full-text available
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...
Article
A temperature rise in soils is usually accompanied by an increase in excess pore fluid pressure due to the differential thermal expansion coefficients of the pore fluid and soil particles. To model the transient behavior of this thermally induced excess pore fluid pressure in geotechnical problems, a coupled thermohydro-mechanical (THM) formulation...
Article
Full-text available
Atmospheric phenomena such as rainfall and evapotranspiration contribute to slope movements in unsaturated soils, the study of which requires fully coupled numerical methods, combined with realistic boundary conditions and appropriate mechanical and hydraulic soil properties. This paper focuses on the effect of the hydraulic behaviour, and in parti...
Article
Full-text available
Thermo-active piles are widely utilised for low carbon heating and cooling, and their uses are further encouraged in cities where there are obligations for developments larger than a certain threshold to generate a portion of their estimated energy use on site in a renewable manner. It is therefore important to model accurately the thermal performa...
Article
Full-text available
Thermo-active retaining structures are geotechnical structures employed to provide thermal energy to buildings for space heating and cooling through heat exchanger pipes embedded within the concrete structure. Consequently, the design of these structures needs to consider both the long-term energy efficiency as well as the thermo-mechanical respons...
Article
Interface elements are frequently employed in finite element (FE) analyses to represent soil-structure interfaces or rock joints. The modelling of coupled thermo-hydro-mechanical (THM) problems in geotechnical engineering requires equally a coupled and robust THM formulation for interface elements. This paper presents such a formulation which is ca...
Article
Full-text available
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...
Article
Full-text available
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...
Article
Full-text available
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....
Article
Full-text available
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...
Article
Full-text available
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...
Article
Full-text available
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...
Conference Paper
Full-text available
Axial stresses are thermally-induced when a thermo-active pile is heated or cooled, as the soil surrounding the pile restricts the expansion or contraction of the pile. In order to investigate the thermally-induced axial stresses a thermo-active pile is subjected to when it is heated, a fully coupled 3D thermal-hydro-mechanical (THM) finite element...
Conference Paper
Full-text available
Thermo-active retaining walls have a great potential for providing low-carbon heating and cooling due to their large contact area with the ground. However, analysing their energy efficiency is complex, as they are not completely surrounded by soil, but partially exposed to the environment, the thermal characteristics of which depend on the function...
Article
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...
Conference Paper
Industry assessment of the structural forces in existing tunnel linings induced by ground movements usually relies on analytical models adopting an elastic solution of a continuous circular ring. This methodology has been previously assessed experimentally, but requires further validation through advanced numerical modelling. In this work, the beha...