SImulation of MONopile installation - JIP SIMON Ahmed Elkadi Deltares 14 February 2019
MOTIVATION Vanbeekimages.com 14 februari 2019 Matchmaking Day 2019 2
Global substructure statistics/trends 2016 Offshore Wind Technologies Market Report D>9m L>80m 14 februari 2019 Matchmaking Day 2019 3
Monopiles XXL D=4m D>9m L>80m 14 februari 2019 Matchmaking Day 2019 4
Why numerical studies of monopile installation process? How do ty parameters such as sand density and stiffness, vibrator frequency, hammer load, interface properties, etc. influence installation process and pile drivability? How does installation method influence axial/lateral pile-soil stiffness and bearing capacity? 14 februari 2019 Matchmaking Day 2019 5
Installation method jacking F dyn F stat Impact driving vibrodriving Grabe et al. F stat 14 februari 2019 Matchmaking Day 2019 6
Innovative installation methods Gentle Driving of Piles - GDP source: Fistuca.com Source: grow-offshorewind.nl 14 februari 2019 Matchmaking Day 2019 7
(Mono)pile installation effects in sand Installation effects Change of stress state and void ratio (density) m Induced (excess) pore water pressures h v 2 g h Ground vibrations/noise Friction fatigue Settlements in the near field Influence on adjacent structures Bearing behaviour Capacity with respect to installation method displacements principal stresses 14 februari 2019 Matchmaking Day 2019 8
2015 NS-VIP project Requirements numerical analysis of installation process Large deformations Dynamic and cyclic loading under high frequencies Saturated sand (coupled-analysis) Generation and dissipation of excess pore water pressures Liquefaction along shaft for vibrated pile Sand is complex material with stiffness, strength, dilation depending on density and stress; a wide range of soil stresses occurs Interaction between monopile and soil (SSI) Realistic computation times! 9
MATERIAL POINT METHOD - MPM 14 februari 2019 Matchmaking Day 2019 10
Numerical Method: Material Point Method - MPM UL-FEM : Mesh node locations are updated as material deforms. MPM : Material points representing the soil move through a fixed mesh. Integration points Material points UL-FEM : mesh deforms with soil MPM : no mesh distortion 14 februari 2019 Matchmaking Day 2019 11
Numerical Method: Material Point Method - MPM Equilibrium equations solved at nodes for displacement increments, mapped to material points. All information is stored at the material points. The mesh could be replaced/ reset at the end of each time step. 14 februari 2019 Matchmaking Day 2019 12
MPM Material Point Method http://www.mpm-dredge.eu/ 14 februari 2019 Matchmaking Day 2019 13
JIP SIMON Vanbeekimages.com 14 februari 2019 Matchmaking Day 2019 14
JIP SIMON project JIP-SIMON is a Joint Industry R&D Project concerning numerical simulation of the installation of monopiles. Based on MPM (Anura3D) Focus on vibratory and impact driving installation methods Duration of project: September 2016-15 March 2019 Research institute project coordinator Consulting, pile testing Offshore contractor Manufacturing installation equipment Manufacturing installation equipment large-scale operator of wind parks Offshore contractor 14 februari 2019 Matchmaking Day 2019 15
JIP SIMON project - activities Development of a 2D-Axisymmetry version of the code Optimization for efficiency and speed New/improved contact formulation Quasi-static solution New/improved constitutive material models Small/medium and full-scale validation Sensitivity analyses Research institute project coordinator Consulting, pile testing Offshore contractor Manufacturing installation equipment Manufacturing installation equipment large-scale operator of wind parks Offshore contractor 14 februari 2019 Matchmaking Day 2019 16
2D axisymmetric MPM 2D-Axisymmetry MPM Number of elements and material points can significantly be reduced compared to 3D simulations In 2D axisymmetric, each particle represents one radian of a ring rotated around the axis of symmetry The rest of formulation of 2D axisymmetric MPM is similar to the 2D axisymmetric formulation of FEM Galavi, V., Tehrani, F.S., Martinelli, M., Elkadi, A.S. & Luger, D. (2018). Axisymmetric formulation of the material point method for geotechnical engineering applications. 9 th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE18) Gain in speed 2D vs 3D 14 februari 2019 Matchmaking Day 2019 17
Validation and verification Validation cases Small/medium scale - Monotonic loading; Jacked installation (as reference) - Cyclic loading - Impact loading Large scale - Impact driven piles Speed-up factor 3D vs 2D plane strain 14 februari 2019 Matchmaking Day 2019 18
Jacked installation: Centrifuge tests Preparation at 1g (pile embedded 10D) Spin-up to 40g (pile still embedded 10D) Installation at 40g v = 10 mm/min, D d = 10D Static load test at 40g v = 0.00167 mm/s, D d = 0.1D Centrifuge tests at Deltares (Huy, 2008) Horizontal effective stress during installation at 40g 19
Jacked installation: Stress change horizontal cross section A- A 0 B 2 4 6 8 B vertical cross section B- B A A B 14 februari 2019 Matchmaking Day 2019 20
Jacked installation: Experimental vs numerical loose sand medium dense sand Static load test Computers and Geotechnics 73 (2016) 58 71 14 februari 2019 Matchmaking Day 2019 21
Small scale, cyclic at low frequency Small scale cyclic installation Pile driving in centrifuge Dimensions of the centrifuge set-up Baskarp sand is used Acceleration = 80 g Stoevelaar et al. (2011) 14 februari 2019 Matchmaking Day 2019 22
Small scale cyclic installation Several tests have been performed. The following tests are selected: RD=66% - Monotonic - Cyclic RD=38% - Monotonic - Cyclic v pile v0 2 Asin(2 t ) 2 v 0 = 1 mm/s A = 0.25 mm/s Tests 4 and 6 Test stages - Initial embedment: 10D = 0.113 m - Gravity is increased to 80 g. - Penetration to another 30D. 14 februari 2019 Matchmaking Day 2019 23
Pile Background Mesh Soil ~ 9000 linear triangle elements 14 februari 2019 Matchmaking Day 2019 24
Background Material Mesh point discretisation + Material Points Uniform distribution of material points ~ 48000 material points 14 februari 2019 Matchmaking Day 2019 25
DeltaSand The Hardening Soil model (GHS) is further extended by adding a kinematic shear hardening to simulate liquefaction: Stiffness, strength and dilation are function of stress and void ratio (state dependent). 14 februari 2019 Matchmaking Day 2019 26
DR = 38% 14 februari 2019 Matchmaking Day 2019 27
D R = 66% 14 februari 2019 Matchmaking Day 2019 28
Impact driven - small scale Dry sand Three different relative densities, namely 40%, 60% and 90% (up to 3% error) Mass of hammer: 3 kg Fall height: 1 m Diameter of tank: 2 m; height: 1.6 m Salgado et al., Geotechnical Testing 34. 14 februari 2019 Matchmaking Day 2019 29
Impact driven - small scale Blow count vs penetration depth has been measured for three relative densities Loose sand: around 40% (38.3 ± 3.0%) Medium dense sand: around 60% (59.3 ± 2.3%) Dense sand: (91.1 ± 2.1%) 14 februari 2019 Matchmaking Day 2019 30
Impact driven - small scale Results 14 februari 2019 Matchmaking Day 2019 31
Impact driven - monopile in saturated sand 7.8m diameter monopile, 0.07m wall-thickness Driven in the North Sea Total length of ~77m, ~34m in the sea bed. Water depth ~40m Boskalis: Van der Kloet Data provided by Boskalis Soil layers: CPT values, relative density Type of hammer Geometry of pile Blow counts at different depths Boskalis: Andreas Duerst 14 februari 2019 Matchmaking Day 2019 32
Impact driven - monopile in saturated sand 14 februari 2019 Matchmaking Day 2019 33
Impact driven - monopile in saturated sand Soil: Hardening Soil model Pile: Rigid 2-phase formulation (dynamic consolidation) Pile embedded initially at 4.7m 3.885 m Moving mesh Compressing mesh 14 februari 2019 Matchmaking Day 2019 34
Results - 4.8 to 13.7m Depth (m) 5 6 7 8 9 10 11 ------ ψ = 4 ------ ψ = 1 ------ ψ = 0.5 Field Data o 12 0 50 100 150 200 Blow Depth (m) Depth 4 5 5 6 6 7 7 8 8 9 9 10 10 11 ------ Permeability =1e-3 m/s ------ Permeability =1e-4 m/s Field Data o 11 12 00 50 50 100 100 150 150 200 200250 Blow Blow 14 februari 2019 Matchmaking Day 2019 35
Impact driven - monopile in saturated sand Total results 15 14 februari 2019 Matchmaking Day 2019 36
Results - 4.8 to 13.7m Vertical effective stress during Hammering Deviatoric strain during Hammering 14 februari 2019 Matchmaking Day 2019 37
Summary The material point method has been further developed, optimized, and successfully applied in simulating the process of monopile installation for impact driving (fieldscale monopile) and low frequency vibratory driving (centrifuge scale) The solution is capable of coping with dynamic cyclic, coupled, large-deformation, soil-water-structure interaction problems Follow-up/ongoing work is focusing on high frequency vibratory installation and insights of the various processes involved in pile installation 14 februari 2019 Matchmaking Day 2019 38
Deltares - Delft Ahmed Elkadi