Geotechnics and Energy 56th Rankine Lecture
Richard Jardine
Geotechniekdag 2017, Breda
7th November 2017
The energy conundrum
Global energy demand rising 20% per decade
Imperative to cut greenhouse gas emissions
Geotechnical contributions towards resolving grand engineering challenge
W J M Rankine: 1820-1872 Thermodynamics & geotechnical pioneer
Three main Parts, each with paired topics
I – Maintaining supplies: Offshore oil & gas platform foundations & deepwater landslide risks
II - Climate change: Geotechnical impact & engineering adaptation
III – Renewable energy: Mono & multi-pile offshore windturbine structures for shallow & deeper water
Broader aspects
Transferring offshore research to civil engineering
And three general geotechnical themes Integrating geology, experiments, analysis & field observations
Collaborative research & engagement with Industry, as cited throughout
Practical tools: “As simple as possible, but no simpler” Measurements & predictions for North Sea foundations
BP Magnus 1982 Wind 9 MN
Waves 130 MN Hutton TLP 1984 Norway 186m
Scotland Denmark Magnus: pile strain gauges & accelerometers Hutton TLP: special sensors Groups of 9x2.1m steel tubes driven 82m, hard glacial tills Similar groups, but under tension High resolution static & storm data Dynamic storm loading data Revolutionary floating Hutton Tension Leg Platform Load-cells, ±0.03mm IC gauges, static & storm monitoring Jardine, McIntosh & Hight 1988
Sea bed 0 Depth, m Stiff clay 10 Dense sand
20 Hard clay
30 Dense to v. dense sand 40
Hard Clay 50
Dense to v. 60 dense sand 1.83m OD piles driven through Courtesy Conoco deep glacial clays & sands Predictive methods Conventional API Pile FE, t-z & p-y soil ‘spring’ curves, elastic group factors
Small strain & FE Stress-path tests, local instruments Non-linear stiffness
Shear G/p΄ = f (εs) Bulk K΄/p΄ = g (εvol)
ICFEP; Mod Cam Clay & Mohr- Coulomb models
Installation & Coulomb interface
Non-linear group interaction Smith 1992
Jardine & Potts 1988, 1993 Foundation stiffness: measurements & predictions Conventional: 4 x too soft Axial Hutton case Group load tonnes “IC” predictions accurate 3500 “Small-Strain” ICFEP
Also at Magnus, axial, 3000 rotational & lateral Jardine & Potts 1993 2500 Kenley & Sharp 1993 2000 Ganendra 1994 Observations
1500 ‘IC’ approach used widely onshore 1000
500 Less offshore use.. Conventional
Poor axial capacity reliability 0 CoVs up to 70% 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Uplift mm Field tests with Imperial College Pile
4.0 Axial load, local σr , τrz & pore pressure, h/R=72 multiple h/R levels Bond, Jardine & Dalton 1991 h, m 3.0 h/R=50 Installation, equalisation & loading Six clay & sand sites in UK & France 2.0 Bond 1989, Lehane 1992, Chow 1997 h/R=27 ‘ICP method’ from field, lab tests & theory; Jardine & Chow 1997, Jardine et al 2005 1.0
h/R=8 Checks: 149 test ICP-05 database Yang et al 2017 Radius R Recent updates: With ZJU, 0 With NGI, UWA & Fugro, Lehane et al 2017 Greatly reduced CoVs, predictive bias eliminated ICP précis
Field SI: CPTu qc profiling & sampling Laboratory: interface shear δ́ , σv́ 0 & clay OCR, Sensitivity St
Base: qb = f (qc)
Shaft: effective stress failure τrz = σ́ rf tan δ́
Sand Clay
Pre-loading σ́ rc = qc f(σv́ 0, h/R*) σ́ rc = σv́ 0 f(OCR, St, h/R*)
2 2 0.5 R* = [Router - Rinner ]
At failure
Compression σ́ rf = σ́ rc + ∆σ́ rd σ́ rf = 0.8 σ́ rc Tension ≈ 25% lower same
Dilation ∆σ́ rd = δr 2G/R δr = pile roughness G = f(qc, σv́ 0)
Courtesy P van Esch, Heerema Applications & checks All Shell platforms from 1996
Instrumented driving & storm response monitoring
Field performance assessed: 13 case histories, Overy 2007
Better reliability & economy, reduced installation risks Critical to marginal projects Overy & Sayer 2007
Sand method:
© Imperial College London API RP2 GEO and ISO Goldeneye Courtesy R Overy, Shell Storm performance?
Shearwater A; piles driven in 1997 Response to ≈20 year storm, December 27th 1998
2.13m OD, 51m: hard clays & dense sand Waves at Tern Single piles push & pull, deck sways; Hunt 1999
Model: API t-z, p-y curves 300 Measured maxima Horizontal sway, mm 200
100
0 0 4 8 12 Significant wave height, m As at Magnus & Hutton, field far stiffer than API model 1+ year after driving & cyclic loading Research questions posed by field experience
Ageing after full pore pressure equalisation? Stiffness & capacity?
Cyclic loading? Impact & assessment for design?
Full stress regime around driven piles? Poorly understood, beyond accurate analysis?
Field: ageing study in dense Dunkirk sand
Steel pipe piles 457mm x 19m Parker, Jardine, Standing & Xavier 1999
Driving is key: Bored piles behave differently! Puech et al 2013
With HSE & PMC
Jardine & Standing 2000, 2012; Jardine, Standing & Chow 2006 Shaft capacity from 1st time tests
Capacities grow markedly over months after driving
Re-tests: more complex & disrupted trends
Tension, kN 3000 235 days
81 days 2000
9 days 1000 Initial stiffness constant
0 0 10 20 30 Pile head displacement, mm Adding tests by Gavin et al 2013 & Karlsrud et al 2014
1st time tension 0.3 3.0 Larvik Meanupdated trend IAC 2.5 Dunkirk Blessington 2.0 QS(t)/ QS(ICP) (ICP) s 1.5 (t)/Q s Q 1.0 End of driving 0.5 Dunkirk - Jardine et al. (2006) Blessington - Gavin et al. (2013) Larvik - Karlsrud et al. (2014) 0.0 1 10 100 1000 10000 TimeTest afterage, installation: days days Governing processes, necessary conditions? Rimoy, Silva, Jardine, Foray, Yang, Zhu & Tsuha 2015 Model: Grenoble calibration chamber experiments with Pierre Foray Electric Jack Jardine et al 2009 Load cell 36mm OD ICP; Fontainebleu NE34 & GA39 sands 0m Wet & dry, Dunkirk ID range -0.33 m C (46R) -0.52 m 150 kPa surcharge B (26R) Constant stress, rigid or -0.79 m ‘active’ radial boundaries Up to 36 sand A (9R) -1.0m stress cells Zhu et al 2009 Stainless & mild steel piles, -1.50m Driven & jacked Post-docs: M Emerson, B Zhu, Z Yang, C Tsuha; PhDs: Rimoy 2014, Silva 2015 Model: radial stresses in NE3450 50 0 0 40 4.0 40 2.0 Heavily pre-loaded sand 0.50 8.0 0.50 4.0 30 12 30 6.0 Intense loading under tip 16 0.50 8.0 0.50 radius r & h = 0 20 20 20 10 0.75 0.75 R σ´ ≈ q ≈ 20 MPa R z c 10 10 / / 1.0 / h σ´r ≈ qc/3 h 1.5 1.0 2.0 0 14 3.0 8.0 4.0 0 3.0 σ´r/qc contours in % 6.0 4.0 2.0 decay with r/R & ± h/R 1.5 0.75 -10 0.75 -10 0.50 And pre-cycled 0.50 -20 -20 Quite unlike bored piles 0.25 0.25 0.25 -30 -30 0 5 10 15 20 0 5 10 15 20 Jardine, Zhu, Foray & Yang 2013 r / R r / R Pile penetrating Load-off pauses Model: arching round shaft after installation Adding SST shaft σ′r data Reveals σ′r maxima at 2 < r/R < 4 σ′r/qc % σ′θ/qc % 3.0 3.0 Radial Hoop 2.5 2.5 h/R=5.6 h/R=5.6 2.0 2.0 h/R=16~21 (%) c (%) c q 1.5 h/R=31.1 h/R=16~21 1.5 q / / ' rs s 1.0 h/R=31.1 ' 1.0 0.5 0.5 h/R=40.6 h/R=40.6 0.0 0.0 0 5 10 15 20 0 5 10 15 20 r /R r /R If arch relaxes through creep σ′r & shaft capacity rise Benchmarks for numerical analyses Yang et al 2014, Rimoy et al 2015 Dataset includes micro-mechanical observations Dense fractured ‘crust’ forms around shaft - as in field From above Side view 0.5 to 1.5mm thickness Laser analysis of breakage Grows with d50 & h Porosity measurements Pile edge 10 mm 36 mm Yang, Jardine, Zhu, Foray & Tsuha 2010 Analysis: Arbitrary Lagrangian-Eulerian FE, with grain crushing Breakage Base q MPa Axis b contours 0 5 10 15 20 25 ~0-2mm 0 ~2-5mm 0.30 0.20 15 ~5-8mm 0.10 0 Pile 30 S/R 1: high crushing Experiment Theory 2: significant 45 3: moderate z, mm 60 S = tip penetration depth Grain breakage R = pile radius None B = 0, Full B = 1 Zhang, Nguyen & Einav 2014 ‘ALE’ FE predictions of arching σ′ /q % σ′ /q % r c θ c 6.0 6.0 h/R=3 4.5 4.5 h/R=6 h/R=3 : % : :% c c 3.0 3.0 q q h/R=6 / / ' ' r 1.5 h/R=9 1.5 h/R=9 0.0 0.0 0 5 10 15 20 0 5 10 15 20 r /R r /R Similar to σ measurements, maxima within 30% Add shaft abrasion & cycling to improve predictions? Or tackle with Discrete Element Method? Zhang, Yang, Nguyen, Jardine & Einav 2014 DEM analysis: Ciantia et al 2017 5 0.4m x 1m ‘sand mass’ - 5x10 crushable d50 =8.5mm grains Matches qb – penetration curve & arching stresses σ′r/qc % σ′θ/qc % 3,0 3,0 2,5 2,5 h/R=6.6 2,0 h/R=6.6 2,0 1,5 1,5 1,0 1,0 h/R=17.9 h/R=17.9 h/R=33.6 h/R=33.6 0,5 h/R=40.3 0,5 h/R=40.3 r/R r/R 0,0 0,0 0 5 10 15 20 0 5 10 15 20 Better h/R trends Analysis converging towards experiments Influence of pile & grain diameters? Interface shear zone controlled by d50 Mini-ICPs: less capacity growth than field New field tests: NGI, UCD & Grenoble-IC Also offshore re-drive checks Confirm shaft capacity growth over time Next objective: stress regime around tubular driven piles? 2.13m OD, 38.5m, very dense sand Borkum Riffgrund, German North Sea Jardine, Thomsen, Mygind, Liingaard & Thilsted 2015 Parallel axial cyclic research Field: Dunkirk piles’ global response Model: local stresses in calibration chamber Laboratory: cyclic element tests Analysis: simplified procedure Practical application: sands & clays Dunkirk field piles: Unstable, Stable or Metastable global response? Q Depends critically on: Qmax N, Qcyclic & Qmean Q cyclic Qmean Related to tension capacity QT Time 45 Qmin 40 Q /Q = Q /Q = 0.42 cyclic T mean T Drained pore pressures 35 30 Marginally Metastable 25 N=200 example 20 N=150 Little effect until N>50 Uplift, mm Uplift, 15 N=100 N=50 10 5 Failure at Nf = 206 0 0 1 2 3 4 5 6 16% capacity loss Time (hours) Global response: 14 Dunkirk field tests 1.0 Unstable Jardine & Standing 2012 Nf < 100 Qcyclic/QT Rapid degradation 0.8 1 41 12 0.6 Meta-stable 13 100 < Nf < 1000 24 206 Modest damage 0.4 1 27 9 3 >221 over tens of cycles >200 345 0.2 >1000 Stable N > 1000 0.0 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 Capacity grows, Qmean/QT stiffness constant Local stress response? Mini-ICP experiments Model: mini-ICP in dry NE34 sand at Dunkirk ID Local interface stress paths Stable: 1000s cycles, capacity grows Unstable: rapid degradation No drift in σ´r or displacements under displacement cycling Intermediate load controlled cases: σ´r drift rates tracked precisely Tsuha, Foray, Jardine, Yang, Silva, & Rimoy 2012; Jardine 2013 Analysis: simple approach from ICP tests Metastable & Unstable τrz cycles compact sand near shaft, σʹr unloads, paths drift towards interface failure Locate metastable, stable boundaries? Relate σꞌ drifts to cyclic loads & N? r Element, model or field pile tests? 'r Design storm: Rainflow & ‘Equivalent Number of cycles’ Bored piles far more susceptible to cycling Tests must model driven pile installation Triaxial tests: modelling ‘pile’ paths Conditioning Pre-stressed ‘OC installation’ stress path: ABD Creep & ageing at B & D Pre-cycling at C Constant volume cycling at D Vary Cyclic Stress Ratio CSR = Δq/ p´ Δq = half peak to trough Drifts in effective stress Δp´ strains & stiffness? ‘Driven pile’ triaxial tests: pꞌ drifts over 4500 cycles Seven CSRs: 0.05 ≤ qcyclic/pʹ0 ≤ 0.5 High resolution sensors: consistent strain & stiffness trends ∆pꞌ/pꞌ % NE34 ∆pꞌ/pꞌ0 % Dunkirk 0 Stable CSR <0.30 Stable CSR <0.30 Metastable Metastable Unstable CSR >0.45 Unstable CSR >0.60 Aghakouchak, Sim & Jardine 2015 HCA - simple shear cycling, Hollow Cylinder Apparatus Track changes in σ´n DisplacementDisplacement transducerTransducer BelloframBellofram cylinder cylinder matching pile conditions Ram Ram Measure σ´1 , σ´2, σ´3 ClampClamp SprocketSprocket and / torque & σꞌ1 angle α torquetransmission transmission chain StepperStepper motor motor for for torsiontorsion RotaryRotary tension tension cylinder cylinder Tie rodTie rod HardinHardin oscillator oscillator Proximity transducers CamCam Prox. transducers α AcrylicAcrylic chamber chamber wall wall SpecimenSpecimen σꞌ1 LoadLoad cell cell Outer cell pressure Outer cell and pore water Pwppressure transducers transducers To foundation 72mm ODTo foundationsample HCA Nishimura 2006 Liu 2015 HCA simple shear: drifts in σꞌn over 4500 cycles ‘Driven pile’ cyclic HCA tests, five CSRs, 0.05 ≤ τcyc /pꞌ0 ≤ 0.45 Basis for predicting pile response ∆σꞌn/σꞌn0 % Dunkirk ∆σꞌn/σꞌn0 % NE34 Stable CSR < 0.20 Stable CSR < 0.20 Metastable Metastable Unstable > 0.30 Unstable > 0.30 Aghakouchak 2015 Analysis: projecting pile response zone limits Aghakouchak 2015 Dunkirk field & triaxial predictions NE34 model & HCA predictions Black curves: pile test results Black curves: pile test results Metastable zone Metastable zone predicted from predicted from triaxial tests HCA tests Parallel laboratory work with clays Jardine, Puech & Andersen 2012 Application in cyclic storm assessment Courtesy BP CourtesyCourtesy Chevron Chevron Clair & Clair Ridge Extreme Captain: EOR project North Sea; new West of Shetland storms; hard & reconfigured platforms; dense sand, glacial tills: Hampson et al 2017 tills & clays: Argiolas & Jardine 2017 Effective contributions on continental shelf What about deepwaterCourtesy? Chevron Deepwater Off the continental shelf Large offshore landslides Gulf of Mexico example – Sigsbee Escarpment Pushing the envelope: 1997-2005, after Evans 2007 Ram Schiehallion Ursa Holstein Hoover Thunder Atlantis Powell Horn Foinaven Diana Horse Mars Marlin Kizomba Girassol Mountain Nakika 0 500 450 500 1000 896 980 988 1225 1300 1311 1350 1500 Depth, m 1463 1646 1844 2000 Landslide risks? 1920 2133 2400 38 Sigsbee escarpment: Gulf of Mexico Kovacevic, Jardine, Potts, Clukey, Brand & Spikula 2012 North 30° N Houston New Orleans 29° N Shelf 28° N 27° N 200 km 26° N Sigsbee Escarpment 94° W 92° W 90° W 88° W Basin floor Sigsbee geomorphology Water depth ≈1500m Developers’ risk analysis: mechanisms & recurrence? Controlled by active geology & sedimentation Spreading, uplifting salt diapirs & thick Quaternary clay layers 40 SEISMIC BASEMAP WITH PROPOSED ATLANTIS LATERALS OIL AND GAS ROUTES Geology: geophysics & deep boreholes MARDI GRAS WEST, GC PHASE XII, 3D SPEC SEISMIC° INLINE 5534, V.E. =2 NORTHWEST SOUTHEAST ≈ 4km ≈ 700m Jurassic salt Lower continental Sigsbee Upper continental Lower Continental shelf Slope EscarpmentSigsbee Upper Continental rise Rise Escarpment Uplifting & spreading salt: constrains & distorts Quaternary sediments 3D SEISMIC LINE ILLUSTRATING GEOLOGIC STRUCTURE OF THE SIGSBEE ESCARPMENT GEMS Figure 4-4 Ground modelling Maximum Depth borehole below1200 sea depth level, m 1800 Horizon 4 2400 Top of Shale Top of Salt 3000 3600 0 1000 2000 3000 4000 Distance, m Quaternary Horizons H6 to H0 include high Ip low residual φꞌ clay layers Routine stability analysis cannot model delayed progressive failure Or predict historical and future slide recurrence periods Numerical ICFEP ‘bottom-up’ modelling of last 600,000 years Alternating medium & high Ip layers added sequentially: Modified Cam Clay Sedimentation on 1o slope towards initial 10o escarpment face 10 slope H3 – 550,000 bp High Ip layers 250m ~100 H4 – 600,000 bp 1,000m Parabolic basal uplift applied from H3 onwards 1st principles modelling: slope genesis & failure Maximum slope ~230 prior to last landslide Rapid run out failure unloads slope 700m Swelling over 1,000s years sediment 250m 236m slow uplift 1,000m Sets conditions for future stability Analysis of slope since last slide Long term swelling, overconsolidation, progressive failure Coupled, strain softening Mohr Coulomb model From triaxial & IC ring shear tests 0 High Ip clay Peak φ’peak =18 c’peak=10kPa 0 Residual φ’res =12 c’res= 0 0 0 Less plastic clays & sand: ductile φ’crit=25 & φ’=30 Non-linear permeability & stiffness from lab tests Predicting future risks 1.3km long failure likely, progressive & delayed mechanism Rupture surface Residual shear zones Plastic layer 500m Recurrence interval: c. 5000 years Critical to project risk assessment Field verification? Local geomorphology & sediment dating Part I – Maintaining oil & gas supplies Contributions to continental shelf & deepwater field developments What about climate consequences & risks? Intergovernmental Panel Climate Change, IPCC, model predictions ‘Business as usual’: 3-5.5°C mean warming by 2100 Mean +1oC from 1750 non-uniform Future trends? NOAA Very likely: less Arctic sea ice & shallow permafrost Likely: more frequent intense precipitation Medium confidence: storm track shifts Increasing flood risks Part II – Addressing climate change 1st Modelling geotechnical response Greatest impact: permafrost Integrated approach, field verification New design tools for adaptive engineering 2nd Practical adaptive engineering Flood defence strengthening on difficult ground Permafrost: depths up to 1km Air Annual mean Snow & vegetation Temp oC 0 Active UK Mean Top Temp Permafrost Siberian study Pole Seasons Analogue Zero Amplitude Temp USASRCPTF 2003 Geothermal Continuous Discontinuous Sporadic gradient Unfrozen Depth North American permafrost 1oC/decade N Alaskan permafrost warming, Romanovsky 2015 0.5 to 1oC/decade air rise in Yukon Thermal creeping landslides in sporadic permafrost ‘YT’ landslide, glacio- 350m fluvial soils Little Salmon Lake, Yukon Lyle et al 2014 NW Territories: thaw-slump features, up to 25m deep & 30ha www.nwtgeoscience.ca/project/summary/permafrost-thaw-slumps Predicting fate of Siberian permafrost Imperial College project for BP Climate: Global IPCC models & local adjustments Imperial College Physics: Reifen & Toumi 2009 Local design tool: coupled Thermo-Hydro-Mechanical THM modelling tool with UPC Barcelona Nishimura, Gens, Olivella & Jardine 2009 Regional: Depths & rates of change in permafrost state? GIS, Engineering Geology & Thermal FE Nishimura, Martin, Jardine, & Fenton 2009 1000 x 1000km region, Lake Baikal, Siberia Maps, atlases & Google Earth Digital Elevation Models & ground reconnaissance Five ground model stereotypes Rolling hills, taiga forest Cambrian to Ordovician sedimentary rocks Permafrost, from 60m thick to absent Three geotechnical profiles A: Alluvial valleys B: Bare rock hills C: Colluvial slopes Photo M Smith Photo: M Smith BP Detailed characterisation: Martin 2009 Geothermal FE Analysis: Nishimura, Martin, Jardine & Fenton 2009 Key ground properties: Top boundary: air temperature Porosity & grading snow cover & surface transfer Porosity Snow 0 0.1 0.2 0.3 0.4 0.5 0 B 11Zoom1 nodes 2 S now CA Zoom 1 55 elem ents AC 20 0.6 m Ground Ssnownow elem ents ] elements 40 A – Alluvium G round m [ 100m100 m 10m10 m B - Bare rock h t C - Colluvium p e 60 D 1m1 m 80 100 Base boundary: regional flux Analysis Aim: predict temperature T variations with depth x & time t ∂u(T) ∂ ∂T 1-D heat equation - λ(T) -q=0 ∂t ∂x ∂x q = heat production/sink u = specific internal energy ∂u(T) ∂ = c ρ 1-φ +c ρ S T φ+c ρ (1-S T )φ T+lρ S T φ ∂t ∂t s s l l l i i l l l c = specific heat ρ = density l = specific latent heat s = solid l = water i = ice Sl = degree of pore liquid-ice saturation φ = porosity λ = thermal conductivity Analysis Conductivity (λ) combines solid (s), liquid (l) & ice (i) 1-φ Slφ (1-Sl)φ λ(Sl)=λs λl λi Freezing function: Sl = f (T) depends on porosity & grading: αρ (1-φ) s -β Sl= T ρ lφ α & β specified for Profiles A, B, C Batch-processing for FE database, hundreds of cases Thermal maps: point-by-point `speed-dating’ matching Surface: Air temperature, snow & ‘nt’ transfer factor, slope & aspect Ground Profile: A, B or C Base flux: 0.02 to 0.05 W/m2 Climate Geology Topography Global AOGCM models Desk, Space Shuttle radar reconnaissance data & satellite Local adjustments Digital Elevation Model Slopes, surface Elevation Surface Profile A, B or C Base flux W/m2 Air temp, snow cover, nt factor φ, Sl Database search Query Return Thermal FE Database of solutions 100s of runs Regional maps Local analysis Results for one 60x80 km area 3 6170000 2 1 6160000 Permafrost top temperatures 0 g n i o Year:h t -0.5 C r o N 4 19406150000 -1 1940 & 2000 predictions: -1.5 -2 Validated against field survey 6140000 3 -2.5 -3 570000 580000 590000 600000 610000 620000 TTOP [oC] 2 Easting 3 6170000 2059 climate: SRES A2 case 2 1 1 6160000 0 g n i h Melting landscape, CH release t -0.5 4 2000r o N 6150000 0 -1 -1.5 Slope & foundation failures -0.5 -2 6140000 -1 -2.5 -3 -1.5 570000 580000 590000 600000 610000 620000 TTOP [oC] Infrastructure distress Easting -2 3 6170000 -2.5 2 1 6160000 -3 0 Adaptive design g n i h t -0.5 2059r o N New THM analysis tool 6150000 -1 Validated: Calgary pipeline tests -1.5 -2 Naples metro ground-freezing 6140000 -2.5 -3 570000 580000 590000 600000 610000 620000 TTOP [oC] Easting Climate change – 2nd topic ‘Nuts & bolts’ of practical geotechnical adaptive design Strengthening flood dikes on weak peat foundations In The Netherlands With Deltares, Rijkswaterstaat & HHNK Water Authority Zwanenburg & Jardine 2015 Uitdam, north of Amsterdam Markermeer Polder, 1.5m below Dike sea level (NAP) 30 km dike fails stability checks Improve at minimum environmental & economic cost? Geotechnical controversies: Models for peat? Zwanenburg 2014 Effects of past loading? Failure mechanics? Drained or undrained? Resolve by field, lab & theoretical studies Google Earth 2014 Uitdam 1.6ha test site Density ρ, Mg/m3 0.8 1.2 1.6 2.0 2.4 2.8 3.2 0 18 boreholes, geological logging -1 Bulk in-situ profiling & lab testing -2 Solid Level -3 m NAP 4.5m -4 Peat 4.5m peat, H2 - H3 Von Post, over clay -5 -6 Clay -7 85% organic, 750 < w < 1200% -8 Yield stress σ’vy, kPa 0 5 10 15 20 25 30 Unit weight ≈ water, low σ´ 0 -1 -2 Thin surface ‘crust’ Level -3 m NAP -4 Mean Oedometer yield: 8 < σꞌ < 14 kPa vy -5 ≈11 kPa -6 B3 Triaxial & DSS: 5 < su < 10 kPa -7 B16 -8 Load tests to failure Six instrumented foundations Range of different geometries Controlled loading to failure Short & long term, Single & multi-stage tests Highly compressible; 1.5m settlement in 6 months under 35 kPa FE Analysis supported by lab & field testing Analysis capturing details of undrained failures Loaded slab Test 1 Loaded slab Test 2 5 m Mechanisms, % shear mobilisation Calibrate laboratory & field tests to iterative back-analyses Develop range of parameter selection routes Apply in dike remedial works In-situ su test calibrations Nkt =CPTu 15.3 NBallBall Penetrometer= 16.5 μ =Field 0.5 Vane Test -1 -1 -1 -2 -2 -2 -3 -3 -3 Level -4 -4 -4 CPTS34 Ball Field m NAP S32 B33 FVT 33 Penetrometerfit fit -5 fit S32 -5 -5 Vane levelm][NAP levelm][NAP levelm][NAP -6 -6 -6 -7 -7 -7 -8 -8 -8 0 5 10 15 20 0 5 10 15 20 0 5 10 15 20 s [kPa] s [kPa] s [kPa] Suu kPa Su kPau Su ukPa Test 6 Area: pre-loading Apply to profile consolidation su gains for multi-stage cases Three calibrated su selection routes for adaptive stability design 1. Factored in-situ tests: CPT, Ball Cone & Field Vane 2. ‘SHANSEP’ su/σ́ v – OCR function 3. Lab: interpretation scheme 20 Field Test 18 1 2 16 3 0.9 Field su = 0.6 σ́ v OCR Operational 14 4 su kPa 6 12 Oedometer mean σꞌ 10 vy 8 6 4 2 0 0 5 10 15 20 25 σꞌv kPa Part II Addressing climate change Modelling ground response & developing adaptive design Simple & complex methods for range of climates, verified in field Could add many more layers of complexity Internationally agreed scientific conclusion: Modelling plus adaptation is not sufficient, greenhouse emissions must fall Part III Supporting renewable energy Aim: reduce offshore wind costs & enable deeper water projects Foundations: up to 30% of capital cost, 22% on average 1st Deeper water sites Apply oil & gas research Address ‘problem’ geomaterial: Chalk 2nd Shallower monopile projects Modernise design: PISA Joint Industry Project With Industry, UK Innovate, Carbon Trust, PISA partners 1st - Multi-pile structures for deeper water Jacket, tripod & floating support structures Sand & clay sites ICP from SI stage: East Anglia One Small strain testing & analysis 102 three-leg platforms, Rattley et al 2017 Borkum West II 40 large tripods Borkum West Wikinger New research for ‘Problem’ sites EAOW Chalk: Wikinger, German Baltic 70 four-leg jackets Borkum West II - German N Sea: Merritt et al 2012, Jardine et al 2015 40 tripods, 2.48m OD piles Dense sands & stiff clays 50 year storm cyclic loading ICP: large cost reductions ≈30m Driving 2.48m dia. piles Photos courtesy Trianel Chalk sites: special problems for large driven piles Exposure under glacial till near Wikinger: Rugen, German Baltic Weak CaCO3 easily damaged by impact & cycling HighlyBlah blah uncertain driving for Wikinger: Advance trials Load bearing? Advance offshore tests From Wikimedia commons Tests on 1.38m OD piles for 70 jacket turbines in chalk: Wikinger Three ground Barbosa,profiles, Geduhn trios ,of Jardine, 1.37m Schroeder OD piles & Horndriven 2015 at each Penetration % chalk WK38 16.2m 20 WK43 30.7m 66 WK70 31.0m 78 WK38 Three piles driven at each Dynamic monitoring WK70 11 to 15 weeks’ set-up WK43 At each location Static tension to failure 2km Instrumented restrike Approx. Cyclic test at WK38 72 Test pile installation, October 2014: 17m Euro budget First fully remote stage-loaded large scale seabed tests; 40m water Driving response: WK43, 1.38m OD pile Blows per 0.25m Instrumented dynamic monitoring: Till Signal matching analysis: h/R* trends Penetration Routine Worrying low driving m design resistances? prediction Re-drives show marked ageing Chalk Linked to onshore ageing & cyclic: plain & ICP piles Measured Barbosa et al 2017 Buckley et al 2017 Deploying test frame: December 2014 Remotely controlled static and cyclic tension load tests Remotely operated seabed load frame For scale 16.66m WK38 turbine location test, 108 days after driving ICP analysis: 10.3MN Buckley 2015 Designers’ prediction Outcome: Wikinger foundations re-designed Chalk: summary Dynamic, static & cyclic offshore tests Initial design proven conservative: good return on investment Research in progress Production pile monitoring Supporting ageing, cyclic & ICP chalk tests onshore in UK Integrated with field studies on monopiles PISA Joint Industry Monopile Project Wind With Oxford & UC Dublin Nacelle Cut costs, enable deeper water Beam use in sands & clays elements Tower Analysis, laboratory & large field tests Wave Transition Replace standard p-y methods peice Low L/D: add extra components Monopile Calibrate: FE & stress path tests Recognise: cyclic response P-y springs Byrne, McAdam, Burd, Houlsby, Martin, Zdravković, Taborda, Potts, Jardine, Sideri, Schroeder, Gavin, Doherty, Igoe, Muir Wood, Kallehave & Skov Gretlund 2015 PISA design method: ‘Simple as possible, but no simpler’ Conventional PISA M M H H z z p p τ τ p p S Mb Only lateral p-y ‘springs’ Four sets of ‘springs’, check by Little scope to capture detailed 28 instrumented driven steel piles soil properties Dunkirk & Cowden test sites 2m diameter piles under cyclic loading at Dunkirk 3-D ICFEP analysis calibrated to advanced lab tests Dunkirk: dense marine sand Two PhD testing programmes: stress path & HCA experiments Cowden: Humberside Sandy glacial till with stones & fissures HCA ‘specimen sculpting’ aided by CT scanning Photos: Liu Research by Ushev & Liu 38 & 100mm D triaxial tests High-resolution local strains Mid-height pore pressure Dual-axis bender elements 72mm OD HCA experiments Control over σ1, σ2, σ3 & α Compressibility, non-linear stiffness & shear strength Anisotropy, strain rate & cyclic dependency 3-D ICFEP soil models Calibrated to laboratory & in-situ tests Cowden: expanded Mod. Cam Clay Dunkirk: Bounding Surface Plasticity σʹ /pʹ Non-linear small 1 Strength variation in deviatoric plane G/p' strain stiffness Log deviatoric strain, % J J/Jcs Effect of Effect of OCR density p' p'/p'cs Zdravković, Taborda, Potts, Jardine, Sideri, Schroeder, Byrne, McAdam, Burd, Houlsby, Martin, Gavin, Doherty, Igoe, Muir Wood, Kallehave & Skov Gretlund 2015 Modelling 2m OD, 10.5m deep, Cowden piles 2500 Field Test 2000 1500 1000 Routine API/ISO/DNV analysis Horizontal Load, kN Load, Horizontal 500 0 Horizontal displacement Routine analysis: far softer than field Modelling 2m OD, 10.5m deep, Cowden piles 2500 Field Test 2000 ICFEP Class A prediction Far better match, 1500 Next task – cyclic loading 1000 Routine API/ISO/DNV analysis Horizontal Load, kN Load, Horizontal 500 0 Equally applicableHorizontal to onshore displacement foundations & caissons One of our ‘broader themes’; the other three? First, integrated approach Geology, experiments, analysis & full scale field behaviour Photo c. 1996 4th Rankine Lecturer, Professor Sir Alec Skempton 1914-2001 Next, broad collaboration Steve Ackerley Andrew Merritt Atkins Amin Aghakouchak Michael Mygind BP Cambridge In-situ Ricardo Argiolas Rory Mortimore Chevron Pedro Barbosa David Nethercot Alan Bolsher Satoshi Nishimura Conoco Phillips Andrew Bond Robert Overy Deltares Róisín Buckley Eric Parker DONG Energy John Burland Duncan Parker EPSRC Byron Byrne David Potts Fiona Chow ESG, formerly PMC Mark Randolph Jim Clarke Michael Rattley Fugro Clive Dalton Siya Rimoy Geotechnical Consulting Group, GCG Bethan Davies Way Way Sim Itai Einav Grenoble Tech, Laboratoire 3S-R Carlos Santamarina Trevor Evans Health & Safety Executive, HSE Felix Schroeder Pierre Foray Matias Silva Iberdrola, Scottish Power Renewables Clark Fenton Philip Smith Innovate UK Liana Gasparre Jamie Standing Lankelma UK Antonio Gens David Taborda Joanna Haigh Offshore Wind Consultants, OWC Ralf Toumi David Hight Oxford University Michael Hotze Christian Le Blanc Thilstead Royal Haskoning DHV Rupert Hunt Cristina Tsuha Emil Ushev Shell UK Graham Keefe Stavroula Kontoe Robert Whittle UPC Barcelona Barry Lehane Zhongxuan Yang University College Dublin Tingfa Liu Lidija Zdravkovic University of Western Australia Christopher Martin Bitang Zhu Zhejiang University Ross McAdam Cor Zwanenburg Finally Fit for purpose practical tools “As simple as possible, but no simpler” Wide spectrum of complexity considered Future challenges, one example per main part I – Stress regime inside & around open driven piles? II – Creeping thermal landslides? III – Cyclic loading of monopiles & caissons? Geotechnical progress towards resolving the energy conundrum? Maintaining safe & efficient offshore oil & gas supplies Addressing climate impact & developing effective adaptation tools Tackling problem at source: improving renewable energy economics Thank you for your patient attention