MICRO TO MACRO ARE UK LINEAR INFRASTRUCTURE GI’S … 2016 - Ben Gilson.pdf · Measurement whilst...
Transcript of MICRO TO MACRO ARE UK LINEAR INFRASTRUCTURE GI’S … 2016 - Ben Gilson.pdf · Measurement whilst...
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Geotechnica 2016 | 6th & 7th July 2016 | Brunel University, London | www.geotechnica.co.uk
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MICRO TO MACRO – ARE UK LINEAR
INFRASTRUCTURE GI’S SUITABLE
FOR INVESTIGATING MASS SOIL PROPERTY
CHARACTERISTICS?
Ben Gilson - Arup
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OUTLINE
1. Context – why linear infrastructure?
2. Geotechnical challenges
3. Soil heave
4. Characterising soil permeability
5. Successes
6. Access to investigate
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1. UK LINEAR INFRASTRUCTURE
Why linear infrastructure?
• National Infrastructure Plan 2014
• ICE State of the Nation Infrastructure 2014
• HM Treasury Budget 2016
• Infrastructure pipeline - 2020
Linear transport infrastructure
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TRANSPORT
Source: https://www.gov.uk/government/publications/national-infrastructure-pipeline-2016
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1. UK LINEAR TRANSPORT INFRASTRUCTURE
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…London Underground, trams…
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* Not an official logo
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2. KEY GEOTECHNICAL CHALLENGES
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Acknowledgments: 3. www.openbuildings.com , 4. www.railengineer.uk
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3. 4.
http://www.openbuildings.com/http://www.railengineer.uk/
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3. HEAVE IN CUTTINGS
• HS2 Phase 1: hybrid Bill submitted, GI ongoing
• HS2 Phase 2: 39% in cutting, of which 41% potential for heave = 14% of the alignment = 54km
• HS3: 80km? 11.2km heave?
• Network Rail stations
• UK Road network
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HS
2 P
hase
1H
S2
Ph
ase
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Acknowledgments: BGS 50k solid and drift geology. Contains British Geological Survey materials © NERC 2016
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3. IMPORTANCE OF GEOTECHNICAL ISSUES
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3. DESIGN FOR HEAVE
• HS2 track displacement criteria (Sartain & Trinder, 2016):
• 30mm post construction (ballast)
• 15mm post construction (slab track)
• 5mm / yr
• Mitigation options:
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2. Over excavation / reduce width
3. Vertical wells to accelerate heave1. Piled slab
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4. SOIL PERMEABILITY
Permeability
Degree of saturation
Swelling / stress level
Cementation
Grain sizeVoid ratio/
cavitation
Hydraulic gradient
Discontinuities
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4. MEASURING SOIL PERMEABILITY
Intrusive GI -Develop
ground model
Laboratory tests
In-situ tests
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EN 1997-1:2004 3.3.9.1
“Whenever possible, in-situ tests, which measure average properties of
a large ground volume should therefore be preferred.”
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4. MEASURING SOIL PERMEABILITY
Intrusive GI -Develop
ground model
Laboratory tests
In-situ tests
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• Triaxial testing
• Oedometer
• Rowe cell
• Hydraulic cell
• Piezocone (CPT)
• Standpipe/piezometer/
packer
• Falling head
• Rising head
• Constant head
• Self boring pressuremeter
• Pulse testing
Micro structure
Stress variation
Saturation and void ratio
Cavitation?
Anisotropy
Macro characteristics
Variations in influencing factors
Discontinuities (e.g. fissures)
Sample disturbance
Rowe (1986)
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4. MEASURING SOIL PERMEABILITY
Intrusive GI -Develop
ground model
Laboratory tests
In-situ tests
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• Triaxial testing
• Oedometer
• Rowe cell
• Hydraulic cell
• Piezocone (CPT)
• Standpipe/piezometer/
packer
• Falling head
• Rising head
• Constant head
• Self boring pressuremeter
• Pulse testing
• Tracer tests
• Geophysical methods
• Flowmeter/impeller
Macro characteristics ???
In-situ stress / saturation
Discontinuities
Anisotropy (SBP)
Future changes: stress, void
ratio, saturation
Logistics, time
Installation effects
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4. MEASURING SOIL PERMEABILITY
Intrusive GI -Develop
ground model
Laboratory tests
In-situ tests
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Field trials
Fehmarnbelt (Morrison et
al, 2015) - excavation
Queensborough bypass
(Nicholson & Jardine, 1981) -
settlement
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4. UNDERSTANDING PERMEABILITY
• Soil mass
• Sand / silt layering
• Groundwater
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CPT Cable percussion Rotary coring
Acknowledgments: Left Lankelma (http://www.lankelma.co.uk/cone-penetration-testing/cpt-rigs/rail-truck/).
Right: HS2 Ground Investigations, a non-technical guide (https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/412948/HS2_ground_investigations_-_a_non-technical_guide.pdf)
http://www.lankelma.co.uk/cone-penetration-testing/cpt-rigs/rail-truck/https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/412948/HS2_ground_investigations_-_a_non-technical_guide.pdf
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4. UNDERSTANDING PERMEABILITY
• Soil mass
• Sand / silt layering
• Groundwater
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CPT
Continuous profile – soil layering
PWP with CPTu
Increased metreage
Sampling limited
Depth limited
Dissipation tests need significant period
to reach equilibrium
Installations limited
Acknowledgments: Lankelma (http://www.lankelma.co.uk/cone-penetration-testing/cpt-rigs/rail-truck/).
http://www.lankelma.co.uk/cone-penetration-testing/cpt-rigs/rail-truck/
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4. UNDERSTANDING PERMEABILITY
• Soil mass
• Sand / silt layering
• Groundwater
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Cable percussion
Groundwater strikes
Risk of wash-out reduced
Sampling quality limited
Significant disturbance
Water for lubrication
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4. UNDERSTANDING PERMEABILITY
• Soil mass
• Sand / silt layering
• Groundwater
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Rotary coring
High sample quality
Complete stratigraphic inspection
Groundwater strikes limited
Core loss in important strata – clay to
sand interface
! Drill fluid
! Workmanship
Acknowledgments: HS2 Ground Investigations, a non-technical guide (https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/412948/HS2_ground_investigations_-_a_non-technical_guide.pdf)
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/412948/HS2_ground_investigations_-_a_non-technical_guide.pdf
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4. BETTER MEASUREMENT OF PERMEABILITY
What do we need, and why?
• Better ‘average’ or governing mass permeability values?
• Increase scale, reduce test time…
• Vary sample volume and understand influencing factors
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K = 1x10-8 K = 1x10-10
PWP PWPPore water pressures after 3 months…
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5. SUCCESSFUL CHARACTERISATION OF MASS
SOIL PROPERTIES - NON-INTRUSIVE
• Characterise soil stiffness
• Downhole logging – stiffness and stratigraphic understanding
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Acknowledgments: left image: Hope et al. (1998)
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5. SUCCESSFUL CHARACTERISATION OF MASS
SOIL PROPERTIES - INTRUSIVE
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1. Triple barrel rotary 2. SEM / XRD 3. Lubricated CPT
4. Westbay standpipe 5. Measurement whilst drilling (MWD)
Acknowledgments: 3) www.lankelma.com; 4) Westbay system Schlumberger water services (2016), www.water.slb.com. 5) Emerson Moore Drilling Ltd. at http://www.geolsoc.org.uk/.
10µm
http://www.lankelma.com/http://www.water.slb.com/http://www.geolsoc.org.uk/
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6. DEEP GI WITH RESTRICTED ACCESS
• Wide tracts of rail land
• >30m deep retaining walls
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6. DEEP GI IN A RAIL ENVIRONMENT
Constraints
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1. Rig toppling
2. Restricted access
Risks
• Casing limitations – weight and torque
• Sampling
• Depth limitations
3. Overhead line equipment (OLE)
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7. CONCLUSIONS
Are UK linear infrastructure GI’s suitable for investigating mass soil property characteristics?
• Innovations & improvements, but many challenges remain.
• Understanding ground conditions – permeability – fine-grained soil – key.
• Robust and refined. Field trials to justify reduced conservatism.
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REFERENCES
• Clayton, C. (2011) Stiffness at small strain: research and practice. Geotechnique 61, No. 1, 5–37
• Deighton, M. & Rigby-Jones, J. (2016) Technical paper: Improved estimation of ground stiffness for railway projects using continuous surface wave testing. Ground Engineering May 2016.
• EN 1997-1:2004 +A1:2013 Geotechnical Design. General Rules.
• Hope, V., Clayton, C. & Sutton, J. (1998) The use of seismic geophysics in the characterization of a weak rock site. Proceedings of the symposium on geotechnical site characterization (eds P. K. Robertson and P. W. Mayne), pp. 479-484. Rotterdam: Balkema.
• Sartain, N., & Trinder, S. (2016) Geotechnical Challenges of HS2. Presentation at 1 Great George Street, 13 March 2016.
• HM Treasury & Infrastructure and Projects Authority (2016) National Infrastructure Pipeline Spring2016, 15 April 2016, https://www.gov.uk/government/publications/national-infrastructure-pipeline-2016.
• Morrison, P., Kammer, J., Hammami, R., Frederiksen, J., Hansen, G. & Humpheson, C. (2015) Fehmarnbelt Fixed Link – trial excavation.
• Nicholson, D. & Jardine, R. (1981) Performance of vertical drains at Queenborough bypass. Geotechnique 31(1) p67-90.
• Rowe, P. (1968) The Influence of Geological Features of Clay Deposits on the Design and Performance of Sand Drains, Proceedings ICE.
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https://www.gov.uk/government/publications/national-infrastructure-pipeline-2016