revised s1120 – mixture design for chemically stabilized soil · revised s1120 –mixture design...

Revised S1120 – Mixture Design for Chemically Stabilized Soil

• Peter Narsavage, PE

2Rev. S 1120 - April 2010

+50 psi

4.7% 5.2%

+505.2 5.5%5.5 + 0.5 = 6%Use 6% in the field.

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Finding S 1120 on the web

• www.dot.state.oh.us

• Divisions > Construction Management > Online Documents > Proposal Notes, Supplemental Specifications, and Supplements

• Document Type: Supplement

• Scroll down to “more…”

Rev. S 1120 - April 2010

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Questions

Peter Narsavage, P.E.

State Construction Geotechnical Engineer, Office of Construction Administration

Ohio Dept. of Transportation

e-mail: [email protected]

ph:(614) 644-6638

cell:(614) 562-1529

Rev. S 1120 - April 2010

GB1/MOP204 Review/Revision

Christopher Merklin, ODOT-OGE

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Reasons for Review/Revision

• Consistency between design (GB1) and construction (MOP204)

• Incorporate base reinforcement (i.e., geogrid) option

• Verify chemical stabilization strength and depth requirements through engineering analysis

• Analyze Rubblize and Roll requirement N60

>15bpf

GB1/MOP 204 Review/Revision

10

Consistency Between Design (GB1) and Construction (MOP204)


0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16

Un

derc

ut

(in

.)

N60

ODOT New Construction

ODOT Re- Construction

GB1

11



12



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• Undercut Design Methodology

– Experience (current GB1, MOP204)

– Modified Steward (USACE, USFS)

– Giroud-Han


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• Inputs

– Subgrade strength

– Vehicle passes

– Equivalent axle loads (wheel loads)

– Axle configurations

– Tire pressure

– Rut depth

– Aperture stability modulus

• Unpaved AnalysisGB1/MOP 204 Review/Revision

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• Subgrade Strength

– Blow counts

– Unconfined compressive strength

– Rut depth

– CBR

Rev. S 1120 - April 2010

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N60 qu (tsf) qu (psi) CBR (qu/2/4.3) Rut Depth (in)

2 0.25 3.47 0.4 12+

4 0.5 6.94 0.8 9

6 0.75 10.42 1.2 8

8 1 13.89 1.6 6

10 1.25 17.36 2.0 4

12 1.5 20.83 2.4 2

14 1.75 24.31 2.8 1


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Rut depth = 1”

1000 passes

80 psi tire pressure

9000 lb wheel load

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0

10

20

30

40

50

60

0.0 1.0 2.0 3.0 4.0

Und

erc

ut

(in)

CBR

Unreinforced

Geogrid

Draft

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0

10

20

30

40

50

60

0 5 10 15

Und

erc

ut

(in)

N60L

Unreinforced

Geogrid

Draft

20



0

10

20

30

40

50

60

024681012

Und

erc

ut

(in)

Rut Depth (in)

Unreinforced

Geogrid

21



Design Charts/Graphs are not Finalized!

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Incorporate Base Reinforcement Option

• Supplemental Specification 861: Geogrid for Subgrade Stabilization (April 17, 2009, modified 7/17/09)

– Average NL < 5 bpf

– Avoid impact on utilities below subgrade

– Avoid difficult maintenance of traffic situations

– Granular thickness>14”, fabric on bottom, grid in middle


23



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• Modeled After FHWA-NHI-07-092, “Geosynthetics Design and Construction Guidelines”


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Chemical Stabilization Strength and Depth Requirements

• Analyze using AASHTO2002 4.4.7.1.1.7, Bearing Capacity of Layered Soils

– Undrained Loading (φ = 0) of a 2-layered cohesive soil system

– Stiff soil over soft soil; assume punching shear

– Assume FS=3


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0

2

4

6

8

10

12

14

16

18

0 0.5 1 1.5 2

Chem

ical T

hic

kness (in

)

qu (tsf)

Chemical Stabilization Thickness

(100 psi) vs qu

Analysis

GB1

MOP204

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0

2

4

6

8

10

12

14

16

18

0 5 10 15 20

Chem

ical T

hic

kness (in

)

N60

Chemical Stabilization Thickness

(100 psi) vs N60

Analysis

GB1

MOP204

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• Conclusions

– 100 psi strength for stabilized layer appears adequate

– May consider chemical stabilization for N60< 5bpf

– Current depth requirements are adequate


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Putting it All Together in the MOP204


0 2 4 8 15 20

0 0.25 0.5 1.0 1.5 2.0 3.0

9" 6" 4" 3" 2" 1" 1/2"Rut Depth from Proof RollerN (blows/ft)

HP (tsf)0

1'

2'

3'

4'

5'

Un

der

cut

Dep

th, f

eet

16" 14" 12" Depth of chemical stabilization

with geogrid& geotextile

with geotextile

DRAFT

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Analyze Rubblize and Roll requirement N60 >15bpf

• Much Rubblize and Roll on BUT/WAR-75-3.76/1.90

– Design CBR = 6

– Average NL = 16

– 19% of borings exhibited NL < 10

– All planned rubblize and roll was successful


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Analyze Rubblize and Roll requirement N60 >15bpf

• Rubblize and Roll on WAR-75-3.40

– 6<NL <10 for 36 of 117 borings

– 11<NL <15 for 35 of 117 borings

• Plan to observe 3,700 feet of R/R where average NL ranges from 10 to 13 bpf (in May 2010)


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GB1, MOP204 Review

Questions?
