Peat Slides in Ireland –Causes and Prescriptions

Dr Mike Long & Dr Noel Boylan*Dr Mike Long & Dr Noel Boylan*

UCD School of Architecture, ,Landscape & Civil Engineering(* Now UWA, Perth, Australia)( , , )

1st May 2009

Institiúid na gCóras Domhanda

An Coláiste Ollscoile Baile Átha CliathEarth Systems Institute

University College Dublin

Web: www.ucd.ie/earthEmail: esi.admin@ucd.ie

DerrybrienDerrybrien and and PollatomishPollatomish 20032003Issue of landslides in Ireland highlighted by these slides in Autumn 2003Issue of landslides in Ireland highlighted by these slides in Autumn 2003Issue of landslides in Ireland highlighted by these slides in Autumn 2003Issue of landslides in Ireland highlighted by these slides in Autumn 2003

Irish Times30.10.2003

Irish Times24.10.2003

Irish Times24.10.2003

Irish Times30.10.2003Irish Times

30.10.2003

PollatomishPollatomish Landslide, Co. MayoLandslide, Co. Mayo

80mm rain in 2 hours+ 40 Failures over 5 kmc. 40 families evacuated, ,Structural damage Repair costs = €3 million

Irish Independent24.09.2003

Derrybrien, Co. Galway, Oct. 2003Photo courtesy

Dr. Paul JenningsAGEC

Ground EngineeringNov. 2003

Heavy rain before second movement phaseHeavy rain before second movement phaseSingle failure, travelling within stream valleySingle failure, travelling within stream valley

Gentle slopes, construction activitiesGentle slopes, construction activities

Photos courtesyKoen Verbruggen, GSI

No families evacuatedNo families evacuatedDamage to roads & bridgesDamage to roads & bridgesg gg g

Pollution & fish killPollution & fish kill

International Dimension NCE, 23/10/2003

(Van Baars, 2005)

Ground Eng., April, 2006

Response

• Formation of multidisciplinary Landslides Working Group (GSI)(GSI)

• Publication of “Landslides in Ireland” (2006) (Ed Ronnie Ireland (2006) (Ed. Ronnie Creighton, GSI)

• GSI landslides database (Charise Mc Keown, GSI)

• 148 events – 46 peat

• Both blanket / raised bog

Are these events unusual?

Lands o’erwhelmed with watery peatFrom Black Knock-laida’s bursting breast

Th B “R thli D i ti P ” (1820)Thomas Beggs “Rathlin a Descriptive Poem” (1820)

Events per century

30

35

25

at

slid

es

15

20

er

of

pea

5

10

Nu

mb

0

5

1400's 1500's 1600's 1700's 1800's 1900's 2000's

Quality of records?

Events per decade since 1900

14

16

10

12

14

at

slid

es

6

8

ber

of

pea

2

4

Nu

mb

0

Influence of climate change?

Events per year since 1991

6

7

4

5

at

slid

es

3

4

ber

of

pea

1

2

Nu

mb

0

Events per month

10

12

8

at

slid

es

6

er

of

pea

2

4

Nu

mb

0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Data for 45 events only

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fatalities

25

Castlegarde

20

liti

es

10

15

er

of

fata

Knocknageeha

5

10

Nu

mb

e

Erris

Knocknageeha

Lisdoonvarna

0

5 Lisdoonvarna

1708 1819 1896 1900

Knocknageeha, 1896

Cork Examiner 30/12/96

Feehan et al. (2008)

Robert Lloyd Praeger(1865 - 1953)

”It was dark cold weather, the Reeks were white with snow, the district a rather desolated one, and I well remember that feeling of depression with which we gazed at that black slimy mass stretching down the valley, somewhere in which lay entombed the bodies ofCornelius Donnelly his wife and six children”Cornelius Donnelly, his wife and six children ….

“Unwise turf cutting, by producing a high face without preliminary draining has frequently been the cause of these accidents. Such was so in the fatal Kerry case.”

Lloyd Praeger, R. “The way y g ythat I went” Figgis (1969)

Parallel events elsewhere

Verdal, Norway, 1893

Video clip

Causal factors I – external factors

Hi h i t it i f ll

Can these be linked to climate change?

• High intensity rainfall

• Long period of dry weather (cracks)

• Sudden loading due to construction

• Excavation in the peat e.g. turf cutting

• Historical land use (grazing, burning etc.)

Boylan et al. (2008)

Causal factors II – internal factors

• Slope inclination

• Peat thickness (NB: local depressions)• Peat thickness (NB: local depressions)

• Slope morphology

• Interface

• Hydrogeology (e.g. pipes, impermeable material b l t)below peat)

6

8

m) Intact6

8

m) Blanket Bog

2

4

6

Peat

Dep

th (m

IntactBlanket Bog

2

4

6

Peat

Dep

th (m

Blanket BogRaised Bog

0 10 20 30 40Slope Angle (Deg)

0

0 10 20 30 40Slope Angle (Deg)

0

(a) (b)

Peat thickness and slope angle at failure site(Boylan et al., 2008)(Boylan et al., 2008)

Recent peat slides in IrelandDate Area Mountain County

14/12/06 GleniffHorseshoe

Benwiskin Sligo

14/12/06 Clare Island Knockmore Mayo

31/12/06 Aasleagh Falls Bengorm Mayo

13/8/08 Geevagh Kilronan Sligo13/8/08 Geevagh Kilronan Sligo

22/8/08 Listowel Ballincollig Hill Kerry

23/9/08 Drumkerrin Corrie Leitrim

Factor No. of cases Comment

High intensity or prolonged

5 Climate change?or prolonged

rainfallchange?

Steep slopes 3

Construction 2Constructionactivities

2

Turf cutting 1

Clare Island -14/12/06

244.5 mm of rain in preceding two weeksSimilar event in 2000 and in the 1940’sWater supply to reservoir cut offWater supply to reservoir cut off

Rainfall

Bengorm, Co. Mayo – 31/12/06

Photos courtesyCáitriona Douglas

NPWS

Reactivated and caused road / bridge closure on N59 with 100 km diversion 19/7/07

Geevagh – 13/8/08 Photos from earlier event in 1984Photos courtesy Prof. Pete Coxon, TCD

38.7 mm or rain on 13th, 59.5mm or rain 13th – 15th

Persons trapped in houses/carsPersons trapped in houses/cars€200,000 damage to local football pitch and clubhouseMinor roads swept away, houses flooded

Ballincollig Hill, Co. Kerry – 22/8/08

21.1 mm rain on 18th

Bridge swept away, houses cut off, roads blockedRivers covered in peat telegraph poles knocked overRivers covered in peat, telegraph poles knocked overConstruction activities on site

Rainfall

EPA Report 28/4/09

Assessment of peat strength and stability UCD Civil Engineeringstability – UCD Civil Engineering• Quantitative assessment of risk of peat slides

• Planning Guidelines1 for wind farm developments • Planning Guidelines1 for wind farm developments require an assessment of peat stability to take place

zw

zInfinite Slope Stability Calculation

W

τ sFOS u=

βN

ββγ CoszSinFOS =

41≥FOS1DOEHLG (2006) Wind Energy Development Guidelines

4.1≥FOS

Need of a Model for Peat Strength

Two choices

Development of realistic (but complicated) model

Use of a more simple model for peat ( p )

of peat behaviour. Must account for at least:

•Fibrous nature of peat

p“strength”

•Gas•Interface strength•Peat hydrogeology

Roughe.g. field vane

More precisee.g. DSS

T-bar and Ball probes

High Quality Sampling

International research projectInternational research project on peat strength

UCD (Lab and field), TU Delft (+ESSM), NGI (sampling and in

it t ti )situ testing)

Sherbrooke block sampling of peat in the Netherlands by TU Delft, NGI, UCD, Dec 2006

UCD-DSS Apparatus

SpecimenAssembly

LoadingCup

Load Balance

100mm

UCD-DSS Apparatus 1

30

40

50

(%

)xy

0

0.5y/H

5

10

20

30

She

ar S

train

,

Engineering Shear Strain

Digital Camera

0

1

2.5

(

%)

i-max

In the xy plane, γxy

0

0.5y/H

1

1.5

2

Inc.

She

ar S

train

,

0

0.5

15

Max

.

Maximum Incremental Shear Strain γi-max

0.5

1

y/H

0

5

10

etric

Stra

in,

(%

)vo

l

Particle Image Velocimetry (PIV) software developed by White et al. (2003)

0

-15

-10

-5

Vol

ume

Volumetric strain, εvol

UCD-DSS … an example

spf = 9.8kPa

8

10(k

Pa)

6

ar S

tres

s

Matrix

4

onta

l She

a MatrixFailureInitiated,spm= 7kPa

0

2

Hor

izo

0 20 40 6010 30 50Shear Strain (%)

0

Field Testing

su-AVG ≈ su-DSS

Standard 10cm2

ConeCone

T-bar Penetrometer100cm2

Ball Penetrometer100cm2

Some conclusions

• Expect such events but plan for them• Expect such events but plan for them

• Produce susceptibility maps?

• More clearly understand link between rainfall and• More clearly understand link between rainfall and slides

• Geotechnical properties of materialsp p

Key UCD Message

• The Innovation Imperative: Productivity growth in the Irish economy has slowed to close to zero. The only way to rediscover productivity growth and be able only way to rediscover productivity growth and be able to sustain it is by innovation and the embedding of the knowledge society.

• The Energy and Climate Change Imperative: We have hugely demanding energy and emission reduction obligations – the only way to meet them is through the use of markets and innovation.

• The Earth Systems Institute response to these imperatives We will be an engine showing how to imperatives - We will be an engine showing how to use research and innovation – smart technology and smart policy - to regain competitiveness and productivity generate jobs and meet our energy and productivity, generate jobs and meet our energy and climate change obligations

Acknowledgements

Geological Survey of Ireland

Lankelma Ltd (UK)Lankelma Ltd. (UK)

François Mathijssen (TuDelft)

Paul Jennings AGECPaul Jennings, AGEC

George Cosgrave, UCD

Thanks for listening!

UCD Earth Systems InstituteMeeting the Challenge of Climate Change Meeting the Challenge of Climate Change

Seminar Series

In collaboration with

Comhar Sustainable Development Council, Environmental Protection Agency, Forfás, Geological Survey of Ireland,

Marine Institute, Met Éireann, Sustainable Energy Ireland & Teagasc

Further details on the seminar series is available at www.ucd.ie/earth

A paper and podcast of this seminar will be available on the ESI website soon, please join the online ESI mailing list for such notifications

ESI email: esi.admin@ucd.ie

UCD Earth Systems InstituteMeeting the Challenge of Climate Change Meeting the Challenge of Climate Change

Seminar Series

Next week...Seminar #19Next week...Seminar #19

Friday 8th May 2009

Royal College of Physicians, 12.30pmRoyal College of Physicians, 12.30pm

Dr. Mark RichardsonUCD School of Architecture, Landscape & Civil Engineering

f fPerformance-based specifications: the key to optimising concrete’s contribution to the climate change

challengechallenge

Further details available at www.ucd.ie/earth