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Subgrade Soil Support and Stabilization. O’HARE Airport Modernization Research Project. Research Progress Presentation – June 30, 2005. Co-PIs: Erol Tutumluer Marshall R. Thompson RA: H.S. Brar. P209. P154. Introduction.
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Subgrade Soil Support and Stabilization O’HARE Airport Modernization Research Project Research Progress Presentation – June 30, 2005 Co-PIs: Erol Tutumluer Marshall R. Thompson RA: H.S. Brar
P209 P154 Introduction • Subgrade performanceis a key factor in the overall pavement performance National Airport Pavement Test Facility - Atlantic City, NJ • This project provides testing and analysis to establish subgrade support and stabilization requirements for O’Hare airport pavements
Introduction (cont’d) • The preliminary concrete pavement design for the O’Hare Modernization Program (OMP): • 15 – 17 inches of PCC Surface • 6-inch Hot Mix Asphalt Base • 6-inch Asphalt Treated Permeable Base (!?) • “Stabilized” Subgrade Zone (SSZ) • Prepared Subgrade • North Runway (9L-27R, 7,500 ft) paving is scheduled first for the Spring 2006 (!?) • Stockpiles of local soil on runway centerline (excavated from the “Deep Pond” nearby) • Primarily fill and cut areas
Research Objectives • Consider pavement design inputs for subgrade support • Modulus of subgrade reaction, k • Consider subgrade support and stabilization requirements with respect to: • Need for subgrade stabilization • Stabilization admixture(s) stabilization • Stabilization depth • Estimate “subgrade support” for various combinations of subgrade stabilization treatments and prepared subgrade conditions
Project Tasks Task 1: Establish the Best Demonstrated Available Technology (BDAT) for subgrade soil evaluation and stabilization (Ongoing) Reports and publications collected & submitted as “Technical Notes” on: • Subgrade strength/stiffness evaluation techniques • Subgrade stability requirements & IDOT Manual • “Working platform” requirements for pavement construction
Project Tasks Task 2: Evaluate currently available data for the subgrade test sections constructed in the Fall of 2003 and the necessity/usefulness of constructing additional subgrade treatment test sections at O’Hare (Effort completed) Plate load tests conducted (8/04) on the test sections: • Plate 1: 12-inch stabilization/compaction – no admixture • Plate 2: 12-inch quicklime fine (40 lb/yd2) & fly ash (80 lb/yd2) stabilization • Plate 3: 12-inch quicklime fine stabilization (40 lb/yd2) • Plate 4: 12-inch lime kiln dust stabilization (40 lb/yd2)
Plate Load Tests Modulus of Subgrade Reaction, k
Project Tasks Task 3: Advise OMP on current and future test section monitoring and field test evaluation programs (Effort completed) Various field tests may be useful to characterize the treated subgrade (OMP will arrange for testing): • Dynamic Cone Penetrometer (8/04) • Light-Weight Deflectometer (8/04) • Clegg Hammer • Geogauge • Heavy Weight Deflectometer (HWD) • Ground Penetrating Radar (GPR) • Seismic Pavement Analyzer, SASW, etc.
Dynamic Cone Penetrometer Light-Weight Deflectometer
Project Tasks Task 4: Evaluate currently available geotechnical/subgrade data for the North Runway with emphasis on the stockpiled “Deep Pond” soils. Recommend further soil sampling & testing to be conducted (by an OMP designated testing firm) (Ongoing) Routine tests to establish representative soils existing for the runway subgrade • Grain size distribution (including hydrometer) • Atterberg limits (LL and PL for PI) • Moisture-density-CBR • PH value & calcareous content • If needed, organic matter content
Preliminary Geotechnical Report Soil sampling & testing conducted by Everest Engineering on OMP Runway 9L-27R - October 2004 Atterberg limits (LL and PL for PI) Boring Logs
Preliminary Geotechnical Report Soil sampling & testing conducted by Everest Engineering on OMP Runway 9L-27R - October 2004 Grain size distribution (including hydrometer)
Preliminary Geotechnical Report Soil sampling & testing conducted by Everest Engineering on OMP Runway 9L-27R - October 2004 Moisture-density-CBR
Preliminary Geotechnical Report Soil sampling & testing conducted by Everest Engineering on OMP Runway 9L-27R - October 2004 Unconfined Compressive Strength, Qu
Soil Sampling: Dec. 04 – Feb. 05 Current scheduled soil sampling & testing from the R9L-27R The Drilling Program • Auger borings, 17 boreholes, MT-1 to MT-17 • 10’ to 45’ depths through fill & cut areas • All reaching down to elev. 640’ in the natural subgrade • 3 North of runway, 3 North edge of runway, 4 under runway, 2 South edge of runway, 2 between runway and taxiway, and 3 under taxiway • SPT and soil sampling at 2.5’ • Moisture content, LL, PI, grain size distribution (%clay) • Shelby tube samples at each location (638’ to 642’) • At least 1 bucket for each major soil in each borehole • Two 5-gallon buckets (60-70 lbs./bucket) for each representative soil (composite sample) to test at the University of Illinois
Project Tasks Task 5: Based on the data and information gathered in Task 4, select (in consultation with OMP) the identified representative soils and recommend an admixture stabilization program (Ongoing) Tests to be conducted at the UIUC Advanced Transportation Research and Engineering Laboratory (ATREL)on both untreated & treated soils • Moisture-Density-CBR • Unconfined Compressive Strength • Resilient Modulus • Permanent Deformation @ 6-psi deviator stress
Project Challenges • Proper sampling of the R9L-27R stockpiled soils • Selecting & identifying representative soil samples • Adequately characterizing the representative soil samples by conductingtests at the UIUC ATREL for • Moisture-Density-CBR • Unconfined Compressive Strength • Resilient Modulus • Permanent Deformation @ 6-psi deviator stress
University of Illinois Laboratory Testing Program at ATREL Advanced Transportation Research & Engineering Laboratory (ATREL)
62 Buckets of OMP Soils Arrived at ATREL from the Drilling Program MARCH 2005
62 Buckets of OMP Soils Arrived at ATREL from the Drilling Program- cont’d MARCH 2005
Grouping of Soils at ATREL Grouping done primarily according to % clay content!..
Admixture Types / Sources • Carmeuse (potential supplier) • South Chicago (dolomitic lime) • Buffington, IN (high calcium lime) • Lime types • Lime Kiln Dust (LKD) • Quicklime fines • Buffington is the primary source (We will work with this & confirm with S. Chicago) so far used in lime treatment
Test Specimen Preparation Air Drying Pulverizing Mixing
Moisture- Density- CBR Results CBR (ASTM D1883) Untreated Proctor Compaction (ASTM D698, D1557)
Group 1 Results Moisture-Density
Group 1 Results California Bearing Ratio (CBR)
Group 2 Results Moisture-Density
Group 2 Results California Bearing Ratio (CBR)
60 50 OMC = 16% 40 CBR 30 20 OMC = 14.1% 10 0 10 12 14 16 18 20 22 24 0% Lime 125 5% Lime OMC =14.1% 120 OMC=16% 115 Dry Density (pcf) 110 105 100 95 10 13 16 19 22 25 Moisture Content % Group 2 Results
Group 3 Results Moisture-Density
Group 3 Results California Bearing Ratio (CBR)
OMC=18.8 % OMC=14.4 % OMC=14.4 % Group 3 Results
Group 4 Results Moisture-Density
Group 4 Results California Bearing Ratio (CBR)
Unconfined Compressive Strength Test Results Cohesive Soils (c, f=0) (ASTM D2166) t sd = s1 – s3(=0) failure C = (s1f)/2 = Qu/2 s3 = 0 s1f s1 s
Resilient Modulus (MR) Testing sd Unconfined: s3 = 0 2-in. in f MR = resilient modulus = sd / er sd : Deviator stress er : recoverable strain Conditioning:200 load applications at s3 = 0, sd = 41 kPa Testing:100 load applications sd = 14, 28, 41, 55, 69, 83, 96, 110 kPa
MR Tests – Soil Samples Cylindrical specimens, 2 in. f by 4 in. high Undisturbed soil samples – Shelby tube (f = 2.8, 4 in.)
s M = - 2.21248 + 29.696 R d 2 R = 0.9497 (ksi) R RESILIENT MODULUS M Typical MR Characterization Greensboro, NC Airport Subgrade Soils 28 24 A-4 soil at OMC A-4 soil at OMC+3 20 Bilinear or Arithmetic Model 16 s M = - 0.6274 + 1820 R d 2 R = 0.6617 12 8 4 s M = - 0.4203 + 8.351 s R d M = 0.0408 + 4.9412 R d 2 R = 0.8715 2 R = 0.8796 0 0 2 4 6 8 10 12 14 16 18 s APPLIED DEVIATOR STRESS (psi) d
Eri Group 2 MR Test Results