Subhamoy Bhattacharya

Subhamoy Bhattacharya
University of Surrey · Department of Civil and Environmental Engineering

PhD (Cantab)

About

297
Publications
321,107
Reads
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5,400
Citations
Citations since 2016
160 Research Items
4446 Citations
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
Introduction
Professor Bhattacharya currently holds the Chair in Geomechanics at University of Surrey, Adjunct Professor of Zhejiang University (China) and is a Visiting Fellow at the University of Bristol. Previously he held the post of Senior Lecturer in Dynamics at University of Bristol, Departmental Lecturer at University of Oxford, Junior Research Fellow at Somerville College (Oxford), 21st COE Fellow at Tokyo Institute of Technology, Staff Engineer at Fugro Limited. His research interests are Dynamic Soil Structure Interaction (Offshore and Seismic)
Additional affiliations
October 2012 - present
University of Surrey
Position
  • Professor (Full)
October 2007 - September 2012
University of Bristol
Position
  • Professor (Associate)
November 2005 - September 2007
University of Oxford
Position
  • Departmental Lecturer in Engineering Science

Publications

Publications (297)
Chapter
Offshore Wind Farms have established themselves as a matured technology to decarbonize energy sources to achieve net-zero. Offshore wind farms are currently being constructed in many seismic-prone zones and the codes/best practice guidelines are not fully developed. The aim of the paper (which is based on the keynote lecture presented at the 7th In...
Article
The discrepancies between the dynamic response obtained with “Beam on the nonlinear Winkler Foundation” method, as a 1D model, and the actual pile behaviour in the liquefiable ground have been identified and marked in the vast body of literature. In this study, a 1D formulation is presented for the soil-pile system which provided considerable insig...
Article
Dynamic characterization of offshore wind turbines (OWTs) is an important design consideration dictating two Limit States: Serviceability Limit State (SLS), and the Fatigue Limit State (FLS). Hence determining the natural frequency of the system considering Soil-Structure-Interaction, is an important design parameter and is also necessary in prelim...
Article
Full-text available
An increasing number of offshore wind farms are being constructed in seismic regions over liquefaction susceptible soils. This paper presents a methodology for the analysis and design of monopiles in seismically liquefiable soils by extending the established "10-step methodology" with an additional 7 steps. These additional steps include assimilati...
Article
The purpose of this paper is to study the behavior of pile-supported structures in liquefiable soils, specifically when the soil surrounding the pile transits from no-liquefaction to full-liquefaction. A series of shaking table tests were performed on four pile-supported structures subjected to different input motions and, as a result, with differe...
Article
Full-text available
Offshore Wind Turbines (OWTs) are dynamically sensitive structures and as a result estimating the natural frequency of the whole system taking into effect the flexibility of the foundation is one of the major design considerations. The natural frequency is necessary to predict the long-term performance as well as the fatigue life. OWTs are currentl...
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Buried pipelines crossing active faults are exposed to excessive soil forces under fault movements due to large relative movement between pipes and the soil surrounding them. As a result, extreme longitudinal strains develop within pipelines under large fault movements and this leads to pipeline failures. Several seismic mitigation techniques were...
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The design of an offshore wind turbine system varies with the turbine capacity, water depth, and environmental loads. The natural frequency of the structure, considering foundation flexibility, forms an important factor in structural design, lifetime performance estimates, and cost estimates. Although nonlinear numerical analysis in the time domain...
Article
Offshore Wind Turbines are increasingly being constructed in seismically liquefiable zones and monopile is one of the main foundation types for water depths of up to about 40 m. Due to the nature of the loading history from wind, wave, and machine loading (1P and 2P/3P), the governing loading on the monopile foundation is asymmetric cyclic overturn...
Article
Offshore wind power is increasingly becoming a mainstream energy source, and efforts are underway toward their construction in seismic zones. An offshore wind farm consists of generation assets (turbines) and transmission assets (substations and cables). Wind turbines are dynamically sensitive systems due to the proximity of their resonant frequenc...
Article
Offshore wind farms are currently being constructed worldwide, and most of the Wind Turbine Generator (WTG) structures are supported on single large-diameter steel piles, commonly known as monopile. One of the challenging design aspects is predicting the long-term deformation of the foundation and, in particular, the accumulation of rotation which...
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Full-text available
Offshore wind farms are currently being constructed worldwide, and most of the Wind Turbine Generator (WTG) structures are supported on single large-diameter steel piles, commonly known as monopile. One of the challenging design aspects is predicting the long-term deformation of the foundation and, in particular, the accumulation of rotation which...
Article
Offshore wind turbines (OWTs) are known to experience modal property and foundation tilt changes during operation. These may negatively influence their serviceability and can lead to failure. To avoid these, a comprehensive characterisation of the behavioural patterns of OWTs, especially emergent large ones supported on monopiles, is necessary. In...
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Extending the use of the p–y curves included in the regulation codes API and DNV to design large-diameter monopiles supporting offshore wind turbines (OWTs) was unsuccessful as it resulted in an inaccurate estimation of the monopile behavior. This had prompted many investigators to propose formulations to enhance the performances of Winkler model....
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An earthquake of magnitude 6.9 hit the city of Izmir (Turkey) on 30 October 2020, resulting in 117 deaths (in Turkey) and considerable economic losses. The earthquake also triggered a tsunami. Following the earthquake, field surveys are being conducted in a Covid-secure way to study and document the damages caused. The earthquake caused significant...
Article
Resilience of bridges in seismic zones can be realised by taking the advantage of rocking isolation which aims at reducing the permanent drifts after a seismic event. The seismic forces at the base of the bridge can be reduced by allowing uplift in the foundation when subjected to ground shaking. Conventional monolithic connection of bridge pier to...
Conference Paper
Full-text available
Offshore wind farms are a collection of offshore wind turbines (OWTs) and are currently being installed in seismically active regions. An OWT consists of a long slender tower with a top-heavy fixed mass (Nacelle) together with a heavy rotating mass (blades) which makes the structure dynamically sensitive. They are constantly exposed to variable env...
Article
The present paper is exhaustive documentation made from the post-earthquake damage survey conducted to analyse the major reasons for structural failure during six earthquakes, occurred over the last decade in the Northeastern region of the Indian subcontinent. In the beginning, an attempt is made to highlight the seismological reasons for the vulne...
Article
Buckling instability of slender piles may occur based on the effect of excessive axial loads acting on a pile with diminishing effective stress and shear strength owing to surrounding soil liquefaction. However, several guidelines for pile design often provide insufficient consideration of buckling failure, and it is significant to study the buckli...
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Full-text available
Large scale offshore wind farms are relatively new construct and they are being deployed in regions prone to earthquakes. Offshore wind farms comprise of both offshore wind turbines (OWTs) and balance of plants (BOP) facilities, such as inter-array and export cables, grid connection etc. An OWT structure can be either grounded systems (rigidly anch...
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Full-text available
Offshore wind turbines are a complex, dynamically sensitive structure due to their irregular mass and stiffness distribution, and complexity of the loading conditions they need to withstand. There are other challenges in particular locations such as typhoons, hurricanes, earthquakes, sea-bed currents, and tsunami. Because offshore wind turbines hav...
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Suction Bucket Jackets (SBJs) need to be fundamentally designed to avoid rocking modes of vibration about the principal axes of the set of foundations and engineered towards sway-bending modes of tower vibration. Whether or not such type of jackets exhibit rocking modes depends on the vertical stiffness of the caissons supporting them. This paper t...
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The paper examines the behaviour of buried continuous pipelines crossing strike-slip faults using experimental and numerical modelling. A newly developed experiment setup is presented along with the derivation of relevant scaling laws and non-dimensional terms governing global response of continuous pipelines to strike-slip faulting. Four model tes...
Article
Dynamic response analysis of wind turbine towers plays a pivotal role in their analysis, design, stability, performance and safety. Despite extensive research, the quantification of general dynamic response remains challenging due to an inherent lack of the ability to model and incorporate damping from a physical standpoint. This paper develops a f...
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Full-text available
Offshore wind farms are a collection of offshore wind turbines (OWTs) and are currently being installed in seismically active regions. An OWT consists of a long slender tower with a top-heavy fixed mass (Nacelle) together with a heavy rotating mass (Hub and blades) and is always exposed to variable environmental wind and wave loads. For dynamic ana...
Article
Full-text available
The conventional design philosophy of bridges allows damage in the pier through yielding. A fuse-like action is achieved if the bridge piers are designed to develop substantial inelastic deformations when subjected to earthquake excitations. Such a design can avoid collapse of the bridge but not damage. The damage is the plastic hinge formation for...
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Bridges are a part of vital infrastructure, which should operate even after a disaster to keep emergency services running. There have been numerous bridge failures during major past earthquakes due to liquefaction. Among other categories of failures, mid span collapse (without the failure of abutments) of pile supported bridges founded in liquefiab...
Chapter
Incorporating realistic soil-structure interaction (SSI) in built environment and major infrastructure projects provides significant beneficial role in terms of economics (i.e., better cost benefit), thereby reducing carbon footprints and enhancing green credentials. Generally, SSI is ignored, and often engineers tend to use Winkler's springs to de...
Chapter
The use of physical modeling in civil engineering design in general and geotechnical engineering, in particular, is not only well established but also highly valued in the engineering community. In geotechnical engineering, physical modeling is even more important as the main material under consideration is soil. Soil is a natural material that for...
Chapter
Full-text available
This chapter presents a concise overview of the mechanics of failure, analysis and requalification procedures of pile foundations in liquefiable soils during earthquakes. The aim is to build a strong conceptual and technical interpretation in order to gain insight into the mechanisms governing the failure of structures in liquefaction and specify e...
Chapter
Physical modeling is an established tool in geotechnical engineering for studying complex interaction problems involving soils. This chapter provides an overarching narrative of different aspects of such physical modeling include the challenging issue of designing meaningful (useful) tests and interpretation of the results for predicting prototype...
Conference Paper
Offshore wind is becoming more attractive day by day due to several reasons, and some of them are scalability in the sense that large power plants can be constructed, higher wind speeds in offshore locations due to lack of obstructions, larger continuous areas and ease of construction. Foundations are one of the critical parts of Offshore Wind Turb...
Article
Simplified design procedures for offshore wind turbine (OWT) support structures are necessary in the concept and tender design stages for assessing the financial viability. Building upon the previous research on simplified monopile design, this paper presents a similar method to design jacket supported OWTs founded on piles or suction caissons. The...
Conference Paper
A large number of buried pipelines are located in seismically active regions. Earthquake related pipeline damage can severely affect a nation's industries, economy, and services. Thus, earthquake resistant design of buried continuous pipelines is one of the significant aspects of geotechnical and structural engineering. Fault movement is one of the...
Chapter
This paper is the written version of the keynote lecture delivered by the first author at the First Indian symposium on Offshore Geotechnics (ISOG: 2019) held in Indian Institute of Technology (Bhubaneswar) in December 2019. Our world is in crisis due to effects of climate change, and one of the possible ways to limit further damage is to decarboni...
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The paper highlights the importance of using site specific shear modulus reduction (G/Gmax versus shear strain, γ) curves and damping ratio (D versus shear strain, γ) curves for ground response analysis. In order to develop comprehensive G/Gmax-γ and D-γ curves (i.e. over a wide range of strain level), two types of apparatus viz resonant column (RC...
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Offshore wind turbines (OWTs) have emerged as a reliable source of renewable energy, witnessing massive deployment across the world. While there is a wide range of support foundations for these structures, the monopile and jacket are most utilised so far; their deployment is largely informed by water depths and turbine ratings. However, the recomme...
Article
In common engineering practice, foundation–soil–foundation interaction of shallow foundations is frequently ignored. This is presumably for cost/benefit reasons, since computationally demanding finite-element and/or boundary element models are required for that purpose, and its effects are usually assumed to be negligible. In this sense, the presen...
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Wind power is among the established renewable energy technologies and has the potential to tackle many of the current technological and societal challenges. Some of them include: Sustainable energy source, reduction of air pollution which is linked to health issues. There are many variants of application of wind power to meet the energy demand. Exa...
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The paper presents a simplified approach to determine the post-cyclic deformation of liquefied sloping grounds. The approach uses instability curves derived from undrained multi-stage (cyclic+monotonic) triaxial tests. It is shown that the salient aspects of the post-liquefaction deformation can be expressed as a function of the state parameter $\p...
Article
Pile-supported river bridges continue to collapse after most major earthquakes in the event of liquefaction. The identified failure mechanisms of piles in liquefied soil are (1) bending failure due to inertial loads of the superstructure and kinematic loads due to the lateral spreading of soil; (2) shear failure due to shear loads; (3) buckling ins...
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Full-text available
The offshore wind turbines are dynamically sensitive, whose fundamental frequency can be very close to the forcing frequencies activated by the environmental and turbine loads. Minor changes of support conditions may lead to the shift of natural frequencies, and this could be disastrous if resonance happens. To monitor the support conditions and th...
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Offshore wind turbine foundations are subject to 10⁷–10⁸ cycles of loadings in their designed service life. Recent research shows that under cyclic loading, most soils change their properties. Discrete Element Modelling of cyclic simple shear tests was performed using PFC2D to analyse the micromechanics underlying the cyclic behaviours of soils. Th...
Conference Paper
Full-text available
This paper presents a state-dependent procedure to evaluate the post-liquefaction behaviour of sand. Analysis of experimental data obtained from monotonic and cyclic triaxial tests are presented to demonstrate that the salient aspects of the post-liquefaction behaviour of clean sand can be captured by a single physical parameter, ie, the state para...
Conference Paper
Full-text available
Permanent Ground Deformations (PGDs) caused by earthquakes threatens pipeline integrity and the resulting soil-pipe interaction problem is often investigated analytically, numerically and experimentally. Buried pipelines experienced severe damage particularly at the vicinity of reverse faults since they are subjected to a combination of bending and...
Conference Paper
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Following the 2016 Kumamoto earthquake sequence, which struck the island of Kyushu in Japan, a reconnaissance mission was conducted in the region affected by the seismic events by the UK-based Earthquake Engineering Field Investigation Team (EEFIT). The sequence caused widespread liquefaction in the coastal areas of Kumamoto Prefecture, arguably du...
Conference Paper
Usually, pile foundations are designed solely to resist the axial load. This simple approach neglects the effects of static, cyclic and/or dynamic lateral loads. Pile-soil interaction during a real earthquake is still now an open issue to be solved and the problem complexity increase in case of liquefiable soil conditions. Despite some methods are...
Article
Life line structures such as elevated flyovers and rail over bridges should remain functional after an earthquake event to avoid possible traffic delays and risk to general public. Generally, restraining the structure by reducing the degrees of freedom often cause serious damages that occurs during a seismic event through yielding of the structural...
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This article presents a comprehensive study of dynamic soil properties [namely, initial shear modulus-Gmax; normalized shear modulus reduction (G/Gmax); and damping ratio (D) variation curves] and pore water pressure parameters of a river bed sand (Brahmaputra sand), sampled from a highly active seismic region (northeast India). Two independent hig...
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Full-text available
To support large wind turbines in deeper waters (30-60 m) jacket structures are currently being considered. As offshore wind turbines (OWT's) are effectively a slender tower carrying a heavy rotating mass subjected to cyclic/dynamic loads, dynamic performance plays an important role in the overall design of the system. Dynamic performance dictates...
Article
Modes of vibration play a dominant role in the design of WTG (Wind Turbine Generator) support structures. It is necessary to choose the overall system frequency such that the modes of vibration do not coincide with the rotor frequencies as well as the wave frequencies. WTG supported on multiple foundations (such as jackets or seabed frames) may exh...
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This article proposes solutions for stiffness estimation of Double-D shaped caisson foundations embedded in three different types of ground profiles (stiffness variation along the depth: homogeneous, linear and parabolic). The approach is based on three dimensional finite element analyses and is in line with the methodology adopted in Eurocode 8-Pa...
Article
This chapter presents the hand calculations that are relevant to different aspects of foundation design based on methods. It is often necessary to cross‐check high‐fidelity finite element calculations. For financial viability of a project, a quick estimation of the sizes of the foundation are needed without the recourse to expensive numerical model...
Article
Wind turbine structures are subjected to dynamic loads and modes of vibration of these structures play a key role in design considerations. This chapter focuses on the modes of vibration. It discusses the design consideration guided by limit states: ultimate limit state, serviceability limit state (SLS) and fatigue limit state. The chapter also dis...
Article
This chapter discusses the geotechnical site investigation and the soil testing required for obtaining the parameters for carrying out the foundation design. It also discusses the advanced soil testing apparatus that may be used to obtain the design parameters. The chapter focuses on ground investigation that is data and ground/soil parameters nece...
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Soil‐structure interaction (SSI) affects the overall behaviour of the wind turbine system: load‐transfer mechanism, modes of vibration and long‐term performance. It shows that stiffness of the foundation is at the heart of many important calculations. Factors include natural frequency of the whole wind turbine, deformations, fatigue, and long‐term...
Article
Offshore wind turbine installation is a unique type of structure due to their geometry and the loads acting on it. This chapter lists the loads and shows that the environmental loads are a mixture of cyclic and dynamic components. The loads depend on the location of the wind farm together with the size and type of the turbine. The chapter discusses...
Article
This chapter provides an overview of the power generation from wind and features of a wind turbine structure. It discusses the overall layout of a wind farm to appreciate the multidisciplinary nature of the subject. The fundamental concepts and understanding of other disciplines and fields not directly related to foundations but are necessary to ca...
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Offshore Wind Turbine (OWT) support structures need to satisfy different Limit States (LS) such as Ultimate LS (ULS), Serviceability LS, Fatigue LS and Accidental LS. Furthermore, depending on the turbine rated power and the chosen design (all current designs are soft-stiff), target natural frequency requirements must also be met. Most of these cal...
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Full-text available
Under repeated seismic loads during an earthquake, increase of pore water pressure in cohesionless, saturated and loose soils leads to decreased shear strength and therefore liquefaction occurs. Literature reports of numerous cases involving damage due to liquefied soil which makes the pile behaviour and performance in liquefied soil even more impo...
Conference Paper
Full-text available
As a consequence of the 2016 Kumamoto earthquake sequence which hit Japan, several signs of liquefaction-induced failure were apparent including boreholes, differential settlement, tilting of houses and lateral spreading. One purpose of this study is to present liquefaction-induced lateral spreading during the 2016 Kumamoto earthquake at Kamiezu La...
Chapter
Offshore wind turbine (OWT) are new type of structures with no track record of long-term performance. The structures are also dynamically sensitive as the natural frequency of these structures are very close (15–20%) to the forcing frequency acting on them. The foundations for OWT are subjected to a combination of millions of cycles of cyclic and d...
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Full-text available
Foundation stiffness plays a crucial role in the stability analysis of structures to incorporate the Soil Structure Interaction (SSI) effects. Current design approaches of estimating foundation stiffness include advanced dynamic finite element, distributed spring approach, and lumped spring approach. The aim of this paper is to overview the differe...
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Full-text available
The use of energy loop(s), fitted into the structural foundation elements dualizes the role of the pile in meeting the structural performance and the thermal comfort demand of the overlying structure. Heat carrier fluid (HCF) is circulated through the loops, to extract or reject heat energy into the ground, during the space heating or cooling opera...
Article
Monopiles are currently the preferred option for supporting offshore wind turbines (OWTs) in water depths up to about 40 m. Whilst there have been significant advancements in the understanding of the behaviour of monopiles, the guidelines on the prediction of long term tilt (Serviceability Limit State, SLS) under millions of cycles of loads are sti...