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Page 1: IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far

IMPACT ~ Breach Physical Modelling

Review of

Modelling Work

Undertaken So Far...

Page 2: IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far

IMPACT - Breach Physical Modelling

Summary• Objectives

• General approach and facilities

• Scaling

• Controlling / assessing soil properties

• Data collection

• Test programme

• Test results so far...

Page 3: IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far

IMPACT - Breach Physical Modelling

Objectives

To provide lab data through which:

• Field test data may be compared and scaling issues (between field and lab) analysed

• Breach formation behaviour may be extrapolated from field test data via multiple lab tests showing effect of variation in:

– geometry / sediment size & grading / construction / embankment condition

• Additional data for numerical model comparison and validation

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IMPACT - Breach Physical Modelling

General approach and facilities:

General approach:

• Programme of 25 lab tests

– 9 Autumn 2002

– 8 Spring 2003

– 8 Autumn 2003

• Scaling field tests at 1:10 (trying to balance scaling effects)

• Using large scale laboratory facilities to extend data sets as much as possible

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IMPACT - Breach Physical Modelling

General approach and facilities:

Facilities:

• Using a large flume (50m x 10m wide)

• Peak discharge >1m3/s (but limited)

• Automated logging of:

– water levels

– flow into flume

– pressure beneath embankment

– u/s vertical velocity profile

– u/s face digital photo shots

– d/s face video footage

Page 6: IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far

Breach Formation

Physical Modelling Flume (earlier model)

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Breach Formation

Physical Modelling Flume (dimensions)

10m

50m0.8m

Flow upto 1.25m3

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IMPACT - Breach Physical Modelling

Flume

Page 9: IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far

IMPACT - Breach Physical Modelling

Flume

Page 10: IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far

IMPACT - Breach Physical Modelling

Scaling• Range of approaches considered

– Mobile bed modelling

– Sediment entrainment / fall velocities

– Reynolds, Froudian etc.

• For non cohesive, considering different approaches, concluded straight geometric scaling

– 1:10

• Review of scaling later within uncertainty assessment

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IMPACT - Breach Physical Modelling

Scaled Sediment

Grain size distribution - Lab Test Series 1

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10 1000 d (microns)

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Target Grading Uniform Grade (250) Steeper Grading (250) Uniform Grade (150)

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IMPACT - Breach Physical Modelling

Scaled Sediment

Grain size distribution - Lab Test Series 1

-20

0

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10 1000

d (microns)

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Uniform Grade (150) redhill 110chelford 52 Mix redhill110+chelford52mix HST 95+chelford 52 HST 95leighton buzzard da 80 mix leighton buzzard da 80+redhill 110redhill 65 mix redhill 65+redhill110

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IMPACT - Breach Physical Modelling

Scaled Sediment

Grain size distribution - Lab Test Series 1

0

10

20

30

40

50

60

70

80

90

100

10 1000d (microns)

Re

lati

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we

igh

t o

f g

rain

s <

d

in

%

Target Grading

MIX redhill110+chelford52+leighton buzzard+sand

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IMPACT - Breach Physical Modelling

Controlling and Assessing Soil Properties

In order to ensure that field and lab tests are similar we need to consider:

• Soil type

– grading

– permeability

– strength

– cohesion

• Construction properties:

– density

– moisture content

Page 15: IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far

IMPACT - Breach Physical Modelling

Controlling and Assessing Soil Properties

Soil type (grading, strength etc.) is determined through lab analysis of the sample. Properties analysed include:

– grading

– permeability

– proctor

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IMPACT - Breach Physical Modelling

Controlling and Assessing Soil Properties

This data permits plotting of the density moisture curve to show optimum compaction.

During construction, optimum compaction is aimed for.

During construction density readings are taken (nuclear density probe) at 9 locations across the bank and at three levels. This permits the degree and consistency of compaction to be identified.

(Test#1 1.79g/cm3; Test#2 1.76g/cm3)

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IMPACT - Breach Physical Modelling

Density Measurement - Nuclear Probe

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IMPACT - Breach Physical Modelling

Data Collection

Automated logging of:

– water levels

– flow into flume

– pressure beneath embankment

– u/s vertical velocity profile

– u/s face digital photo shots

– d/s face video footage

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IMPACT - Breach Physical Modelling

Data Collection

Page 20: IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far

IMPACT - Breach Physical Modelling

Data Collection

Page 21: IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far

IMPACT - Breach Physical Modelling

Data Collection

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IMPACT - Breach Physical Modelling

Test Programme

Programme of 25 lab tests

• 9 Autumn 2002

– Non cohesive

– Prior to Autumn 2002 field work

• 8 Spring 2003

– Cohesive

– Prior to Autumn 2003 field work

• 8 Autumn 2003

– TBA (piping?)

– Post Autumn 2003 field work

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IMPACT - Breach Physical Modelling

Test Programme - Autumn 2002

• Lab Test#1 Trial / test experiment

• Lab Test#2 Steeper sediment grading - D50 Field Test#2

• Lab Test#3 Repeat Lab Test#2

• Lab Test#4 Breach location (initiate at side of channel)

• Lab Test#5 Scaled grading of Field Test#2

• Lab Test#6 Vary geometry (Crest 2m, Slope 1:2)

• Lab Test#7 Vary geometry (Crest 3m, Slope 1:2)

• Lab Test#8 Steeper grading, different D50

• Lab Test#9 SS Seepage or 2nd D50 variation

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IMPACT - Breach Physical Modelling

Test Programme - Spring 2003

Programme to be agreed.

Objectives to:

• Integrate with Norwegian field work

• Integrate with other European and US experimental work

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IMPACT - Breach Physical Modelling

Test results so far...• Tests 1-5 completed (probably!)

• Tests 6-9 within next 2-3 weeks

• Steady state seepage an issue

• Data from first tests yet to be processed, however photo and video footage is available...

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IMPACT - Breach Physical Modelling

Test results so far...

Breach features noted in Tests 1-3:

• (Seepage and slumping of d/s face)

• Initial vertical cut through bank

– Rapid cut back of d/s face in line with ‘slot’

– Likely significant erosion below ‘bed’ level

• Vertical sides of breach

• Side cracking and slumping

• Upstream slope (face) remains in place as weir for considerable time (flow control)

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IMPACT - Breach Physical Modelling

Test results so far...

Still photo series Test 2

Still photo series Test 3

AVI footage Test 2

AVI footage Test 3


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