Developing confidence in critical state soil … confidence in critical state soil mechanics 5....

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Developing confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015

Transcript of Developing confidence in critical state soil … confidence in critical state soil mechanics 5....

Page 1: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

Developing confidence in critical state soil mechanics

5. Modified Cam Clay (MCC)

Mike Jefferies, PEng

Dr. Dawn Shuttle, PEng

January, 2015

Page 2: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

Why Modified Cam Clay (MCC) ?

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∆εvp

∆ε q

p

Page 3: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

Modified vs Original Cam Clay

OCC MCC

Flowrule

Yield Surface

Hardening

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η

M=

2 pc

p−1

η

M=1 − ln

p

pc

η−= MDp

&pc

pc

=1+ e

λ −κ&εv

p

Dp =

M2 − η2

η2

&pc

pc

=1+ e

λ −κ&εv

p

Page 4: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

Stress dilatancy (= flowrule)

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Mod Cam ClayOriginal Cam Clay

Nova

Rowe

M

Page 5: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

5

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

-1 -0.5 0 0.5 1 1.5

Dp

ηη ηη

D662D667

jjjjqjq

jjjjvjvp

jGqq

KppD

3/)()(

/)()(

111,1,

111,1,

−+−+

−+−+

−−−

−−−=

εε

εε

Stress dilatancy of Erksak sand

Page 6: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

Implementing MCC

� Make copy of the OCC worksheet

� Rename it MCC

� Change

� Spacing ratio to 2

� Dp equation to MCC dilation

� η equation to MCC yield surface

� MCC is “pathological” on dilation

� Must kludge the spreadsheet

� Switch to incrementing volumetric strain for first ~0.5% strain

� Thereafter revert to incrementing shear strain

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Page 7: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

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Implementing MCC by modifying MCC sheet

Page 8: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

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Implementing MCC by modifying MCC sheet

Page 9: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

Over to you…

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Page 10: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

Computed soil response

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Original Cam ClayModified Cam Clay

Page 11: Developing confidence in critical state soil … confidence in critical state soil mechanics 5. Modified Cam Clay (MCC) Mike Jefferies, PEng Dr. Dawn Shuttle, PEng January, 2015 ...

Mod Cam Clay

� “Improved theory” simply shows lack of understanding

� Work dissipation is unclear / unreasonable

� Mathematically “pathological” to implement

� Does not fit any known soil data

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