Revised S1120 – Mixture Design for Chemically Stabilized Soil · Revised S1120 –Mixture Design...
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Transcript of Revised S1120 – Mixture Design for Chemically Stabilized Soil · Revised S1120 –Mixture Design...
6
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
7
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
9
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)
GB1/MOP 204 Review/Revision
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
13
Consistency Between Design (GB1) and Construction (MOP204)
• Undercut Design Methodology
– Experience (current GB1, MOP204)
– Modified Steward (USACE, USFS)
– Giroud-Han
GB1/MOP 204 Review/Revision
14
Consistency Between Design (GB1) and Construction (MOP204)
• 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
15
Consistency Between Design (GB1) and Construction (MOP204)
• Subgrade Strength
– Blow counts
– Unconfined compressive strength
– Rut depth
– CBR
Rev. S 1120 - April 2010
16
Consistency Between Design (GB1) and Construction (MOP204)
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
GB1/MOP 204 Review/Revision
17
Consistency Between Design (GB1) and Construction (MOP204)
GB1/MOP 204 Review/Revision
Rut depth = 1”
1000 passes
80 psi tire pressure
9000 lb wheel load
18
Consistency Between Design (GB1) and Construction (MOP204)
GB1/MOP 204 Review/Revision
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
19
Consistency Between Design (GB1) and Construction (MOP204)
GB1/MOP 204 Review/Revision
0
10
20
30
40
50
60
0 5 10 15
Und
erc
ut
(in)
N60L
Unreinforced
Geogrid
Draft
20
Consistency Between Design (GB1) and Construction (MOP204)
GB1/MOP 204 Review/Revision
0
10
20
30
40
50
60
024681012
Und
erc
ut
(in)
Rut Depth (in)
Unreinforced
Geogrid
21
Consistency Between Design (GB1) and Construction (MOP204)
GB1/MOP 204 Review/Revision
Design Charts/Graphs are not Finalized!
22
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
GB1/MOP 204 Review/Revision
24
Incorporate Base Reinforcement Option
• Modeled After FHWA-NHI-07-092, “Geosynthetics Design and Construction Guidelines”
GB1/MOP 204 Review/Revision
25
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
GB1/MOP 204 Review/Revision
26
Chemical Stabilization Strength and Depth Requirements
GB1/MOP 204 Review/Revision
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
27
Chemical Stabilization Strength and Depth Requirements
GB1/MOP 204 Review/Revision
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
28
Chemical Stabilization Strength and Depth Requirements
• Conclusions
– 100 psi strength for stabilized layer appears adequate
– May consider chemical stabilization for N60< 5bpf
– Current depth requirements are adequate
GB1/MOP 204 Review/Revision
29
Putting it All Together in the MOP204
GB1/MOP 204 Review/Revision
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
30
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
GB1/MOP 204 Review/Revision
31
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)
GB1/MOP 204 Review/Revision