MICRO TO MACRO ARE UK LINEAR INFRASTRUCTURE GI’S … 2016 - Ben Gilson.pdf · Measurement whilst...

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…

*

* 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

1. 2.

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

2

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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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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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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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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• Soil mass


• 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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• Soil mass


• 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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• Soil mass


• 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

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