2. Co-PIs: Erol Tutumluer Marshall R. Thompson RA: H.S. Brar Subgrade Soil Support and Stabilization O’HARE Airport Modernization Research Project

3. Introduction Subgrade performance is a key factor in the overall pavement performance Subgrade performance is 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 This project provides testing and analysis to establish subgrade support and stabilization requirements for O’Hare airport pavements P154 P209

4. Introduction (cont’d) The preliminary concrete pavement design for the O’Hare Modernization Program (OMP): The preliminary concrete pavement design for the O’Hare Modernization Program (OMP): 15 – 17 inches of PCC Surface15 – 17 inches of PCC Surface 6-inch Hot Mix Asphalt Base6-inch Hot Mix Asphalt Base 6-inch Asphalt Treated Permeable Base6-inch Asphalt Treated Permeable Base “Stabilized” Subgrade Zone (SSZ)“Stabilized” Subgrade Zone (SSZ) Prepared SubgradePrepared Subgrade North Runway (9-27) paving is scheduled first for the Spring 2006 North Runway (9-27) paving is scheduled first for the Spring 2006 Stockpiles of local soil on runway centerline (excavated from the “Deep Pond” nearby)Stockpiles of local soil on runway centerline (excavated from the “Deep Pond” nearby) Primarily fill and cut areasPrimarily fill and cut areas

5. Research Objectives Consider pavement design inputs for subgrade support Consider pavement design inputs for subgrade support Modulus of subgrade reaction, k Modulus of subgrade reaction, k Consider subgrade support and stabilization requirements with respect to: Consider subgrade support and stabilization requirements with respect to: Need for subgrade stabilization Need for subgrade stabilization Stabilization admixture(s) stabilization Stabilization admixture(s) stabilization Stabilization depth Stabilization depth Estimate “subgrade support” for various combinations of subgrade stabilization treatments and prepared subgrade conditions Estimate “subgrade support” for various combinations of subgrade stabilization treatments and prepared subgrade conditions

6. Project Tasks Task 1: Establish the Best Demonstrated Available Technology (BDAT) for subgrade soil evaluation and stabilization Reports and publications collected & submitted as “Technical Notes” on: Subgrade strength/stiffness evaluation techniquesSubgrade strength/stiffness evaluation techniques Subgrade stability requirements & IDOT ManualSubgrade stability requirements & IDOT Manual “Working platform” requirements for pavement construction“Working platform” requirements for pavement construction

7. 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 Plate load tests conducted (8/04) on the test sections: Plate 1: 12-inch stabilization/compaction – no admixturePlate 1: 12-inch stabilization/compaction – no admixture Plate 2: 12-inch quicklime fine (40 lb/yd 2 ) & fly ash (80 lb/yd 2 ) stabilizationPlate 2: 12-inch quicklime fine (40 lb/yd 2 ) & fly ash (80 lb/yd 2 ) stabilization Plate 3: 12-inch quicklime fine stabilization (40 lb/yd 2 )Plate 3: 12-inch quicklime fine stabilization (40 lb/yd 2 ) Plate 4: 12-inch lime kiln dust stabilization (40 lb/yd 2 )Plate 4: 12-inch lime kiln dust stabilization (40 lb/yd 2 )

8. Plate Load Tests Modulus of Subgrade Reaction, k

9. Project Tasks Task 3: Advise OMP on current and future test section monitoring and field test evaluation programs Various field tests may be useful to characterize the treated subgrade (OMP will arrange for testing): Dynamic Cone Penetrometer (8/04)Dynamic Cone Penetrometer (8/04) Light-Weight Deflectometer (8/04)Light-Weight Deflectometer (8/04) Clegg HammerClegg Hammer GeogaugeGeogauge Heavy Weight Deflectometer (HWD)Heavy Weight Deflectometer (HWD) Ground Penetrating Radar (GPR)Ground Penetrating Radar (GPR) Seismic Pavement Analyzer, SASW, etc.Seismic Pavement Analyzer, SASW, etc.

10. Light-WeightDeflectometer Dynamic Cone Penetrometer

11. 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) Routine tests to establish representative soils existing for the runway subgrade Grain size distribution (including hydrometer)Grain size distribution (including hydrometer) Atterberg limits (LL and PL for PI)Atterberg limits (LL and PL for PI) Moisture-density-CBRMoisture-density-CBR PH value & calcareous contentPH value & calcareous content If needed, organic matter contentIf needed, organic matter content

12. 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 Non-routine testing to be conducted at the UIUC Advanced Transportation Research and Engineering Laboratory (ATREL) on both untreated & treated soils Triaxial testing for Shear strengthShear strength Resilient modulusResilient modulus Permanent deformationPermanent deformation

13. Project Challenges Properly sampling the “Deep Pond” stockpiled soils Properly sampling the “Deep Pond” stockpiled soils Selecting & identifying representative soil samples Selecting & identifying representative soil samples Adequately characterizing the representative soil samples by conducting non-routine tests at the UIUC ATREL for Adequately characterizing the representative soil samples by conducting non-routine tests at the UIUC ATREL for Shear strengthShear strength Resilient modulusResilient modulus Permanent deformationPermanent deformation

14. Project Deliverables Technical Notes will be prepared and submitted to the OMP throughout the duration of this project to communicate specific findings and recommendations to OMP engineers as needed Technical Notes will be prepared and submitted to the OMP throughout the duration of this project to communicate specific findings and recommendations to OMP engineers as needed A Final Report will be prepared at the end of the one-year study A Final Report will be prepared at the end of the one-year study Several of the Project Tasks are already pursued simultaneously, and the specific delivery of results will be contingent upon availability of OMP data and other factors that depend on coordination with OMP Several of the Project Tasks are already pursued simultaneously, and the specific delivery of results will be contingent upon availability of OMP data and other factors that depend on coordination with OMP

15. Advanced Transportation Research & Engineering Laboratory (ATREL) - University of Illinois:

16. Mechanical Behavior of Subgrade Soils Strength: Maximum level of stress soil can sustain before it fails or excessively deforms Strength: Maximum level of stress soil can sustain before it fails or excessively deforms Shear strength,  max = c +  normal *tan  c: cohesion &  : internal friction angle Stiffness: Stress obtained for a unit strain Stiffness: Stress obtained for a unit strain Resilient (M R ) modulus, Poisson’s ratio ( ) Resistance to Permanent Deformation: Ability to resist a large number of load cycles without accumulating excessive deformations Resistance to Permanent Deformation: Ability to resist a large number of load cycles without accumulating excessive deformations  p = f (N, confinement, cyclic  or ,  /  max )

17. Sample Preparation - Compaction Improve strength, reduce deformation, and prepare specimens close to field construction conditions (OMC: Optimum moisture content) Laboratory Compaction Methods Static – Standard for soils (AASHTO T-307-99), typically 5 layers Static – Standard for soils (AASHTO T-307-99), typically 5 layers Impact – Proctor type ( AASHTO T-99/180 ), several layers Impact – Proctor type ( AASHTO T-99/180 ), several layers Vibratory – Typically used for granular materials Vibratory – Typically used for granular materials  Vibration in several layers (vibratory hammer)

18. Std & Modified Proctor Compaction (ASTM D698, D1557) 110 114 118 122 126 130 56789101112131415 Gravimetric Moisture Content (%) Dry Unit Weight (pcf) w opt  dmax Moisture-Density Relationship

19. 85 90 95 100 105 110 115 120 10141822263034 Moisture Content, % Dry Density, pcf ASTM D-1557 Intermediate ASTM D-698 100 % Sr (Gs = 2.71) 90 % Sr Dupont Clay Typical Moisture-Density Results

20. STRENGTH BEHAVIOR

21. Load stress distribution Subgrade AC Base  c = Confining stress =   d = Deviator stress = v - c v = Vertical stress = c + d    c  c  c  c =  v +  d  3 Triaxial Conditions/Tests  1 =

22. Triaxial Testing Equipment - CapabilitiesMonotonic/Cyclic Axial Load (haversine load shape) Constant/Variable Cell Pressure (air or liquid) Radial Strain Measurement Axial Strain Measurement CylindricalSpecimen Test requires: Pneumatic to servo- hydraulic loadingPneumatic to servo- hydraulic loading Data acquisition system with feedback controlData acquisition system with feedback control Personal computer with an integrated software packagePersonal computer with an integrated software package Modern equipment, good technician, careful equipment calibration!..Modern equipment, good technician, careful equipment calibration!.. 3 1

23. Strength Tests Using Triaxial Setup  C = (  1f )/2 = Q u /2  1111  1f  3 = 0  d =  1 –  3 (=0) failure Cohesive Soils (c,  =0)Cohesive Soils (c,  =0) –Modified Proctor Procedure A (ASTM D1557) –Unconfined Compression (ASTM D2166) Sandy Soils (c,  )Sandy Soils (c,  ) –Modified Proctor Procedure C (ASTM D1557) –Rapid Triaxial Shear (UI Procedure)

24. 50 60 051015 Axial Strain, % Axial Stress, psi MC = 28.5 % DD = 93.5 pcf CBR = 4 MC = 23 % DD = 103.5 pcf CBR = 14 MC = 26 % DD = 98 pcf CBR = 8 MC = 30.5 % DD = 92.5 pcf CBR = 2.5 Dupont Clay Typical Unconfined Stress-Strain Data Q u = unconfined compressive compressive strength strength = peak  1 = peak  1

25. Strength Testing Slow, monotonic 1%/minute UI Rapid Shear: 12.5%/second  d = deviator stress stress  3 = cell pressure pressure dd 33 33 33 C L  max = c +  n *tan  at  3 levels 6.9 kPa = 1 psi FAA NAPTF P209 Aggregate

26. MODULUS BEHAVIOR

27. Elastic (Resilient) Behavior Due To Repeated/Cyclic Load Application MR = d / rMR = d / rMR = d / rMR = d / r  d = Repeated wheel load stress load stress  r = Recoverable (rebound) strain (rebound) strain M R = Resilient modulus Deformation Time Permanent Deformation RecoverableDeformation dddd 3333 3333 3333CL Elastic (Resilient) Modulus, E (M R ) Poisson’s ratio, Poisson’s ratio,

28. Resilient Modulus (M R ) is a fundamental material propertyResilient Modulus (M R ) is a fundamental material property –Simulates repeated application of wheel loads M R testing is a rational test and is an improvement over CBRM R testing is a rational test and is an improvement over CBR M R considers fundamental effects:M R considers fundamental effects: –Stress condition, density, grading, fines, water content Evaluates rutting - very importantEvaluates rutting - very important Resilient Modulus – Overview

29. Lab Testing: AASHTO T 307-99 (SHRP TP46)Lab Testing: AASHTO T 307-99 (SHRP TP46) –Undisturbed –Disturbed, remolded and compacted –Input to mechanistic based pavement design procedures Estimate from various proceduresEstimate from various procedures –Backcalculation from field FWD deflections –Soil properties –Unconfined compressive strength –CBR Determining Resilient Modulus

30. Repeatedly applied loadsRepeatedly applied loads –Similar to those from wheel loads Relates to elastic component of response onlyRelates to elastic component of response only –Resilient (= recoverable) deformation Resilient Modulus Test (AAHSTO T307-99) Type I: Unbound granular base and subbase materials Type II: Untreated subgrade soils, A-4, A-5, A-6, A-7

31.  1 -  3 = Repeated (Cyclic) Deviator Stress Deviator Stress =  d =  d 3333  2 =  3  3 = Confining Pressure (minor principal stress) (minor principal stress) Total Axial Stress,  1 Total Axial Stress,  1 (major principal stress) (major principal stress) Bulk Stress:  =  1 +  2 +  3 =  d + 3  3 =  d + 3  3 Shear Stresses  0   0 M R =  d /  r Vertical Specimen Deformations Measured Only!.. Repeated Load Triaxial Test Stress States

32. M R Tests – Type II Soil Samples Cylindrical specimens, 2 in.  by 4 in. high Undisturbed soil samples – Shelby tube (  = 2.8, 4 in.)

33. 33 dd 33 33   (kPa) 41 21 0 14 1 28 2 41 3 dddd (kPa) 55 4 69 5 14 6 28 7 41 8 55 9 69 10 14 11 28 12 41 13 55 14 69 15 1 : testing sequence 1 : testing sequencenumber Stress Sequence – Type II Soils Haversine load waveform (pulse load duration: 0.1 sec., 5 Hz) Haversine load waveform (pulse load duration: 0.1 sec., 5 Hz) Conditioning: 1000 load applications Conditioning: 1000 load applications at  3 = 41 kPa &  d = 28 kPa (  1 /  3 = 1.7 only!..) at  3 = 41 kPa &  d = 28 kPa (  1 /  3 = 1.7 only!..) Testing: 100 load applications at 15 following stress states: Testing: 100 load applications at 15 following stress states: AASHTO T307-99 - SHRP Protocol P46

34. Aggregate Subgrade soil Wheel AC Subgrade Deviator Stress P dddd  3 = low !..

35. dddd Haversine load waveform (pulse load duration: 0.1 sec., 5 Hz) Haversine load waveform (pulse load duration: 0.1 sec., 5 Hz) Conditioning: 200 load applications Conditioning: 200 load applications at  3 = 0,  d = 41 kPa at  3 = 0,  d = 41 kPa Testing: 100 load applications at 8 following stress states: Testing: 100 load applications at 8 following stress states:  d = 14, 28, 41, 55, 69, & also 83, 96, 110 kPa & also 83, 96, 110 kPa  d = Repeated Deviator Stress Unconfined:  3 = 0 University of Illinois M R Testing Procedure - Type II Soils 2-in. in 

36. University of Illinois – Repeated Load Triaxial Test System

37. Primary Factor Applied stress states,  d and  3Applied stress states,  d and  3 Secondary Factors – soil properties Moisture content, w (or Saturation, S R, %)Moisture content, w (or Saturation, S R, %) –Suction = f(depth to groundwater table) Plasticity index, PIPlasticity index, PI Clay content, % (smaller than 2  m)Clay content, % (smaller than 2  m) Dry density,  dDry density,  d Freeze-thaw effectsFreeze-thaw effects Factors Affecting M R of Type II Soils Fine-grained subgrade soils: silts and clays

38. Nonlinear stress dependent behavior – Stress softening (fine-grained soils) – Stress hardening (coarse-grained, aggregates) Stress Dependent M R Behavior   cohesive soils aggregates linear elastic M R = f (  ) pp

39. M MKKK Rd =+- 132 ( )  when when  d < K < K 2 M MKKK Rd =-- 142 ()  when when  d > K > K 2 dddd K3K3K3K3 K4K4K4K4 1 1 K1K1K1K1 MRMRMRMR K2K2K2K2 Thompson and Robnett (1979) where  d =  1 -  3 Arithmetic or Bilinear Model M R = f(  d ), Mainly Shear Stress Cohesive Soils: K 1 = E ri = Breakpoint modulus K 2 =  db = Breakpoint deviator stress deviator stress = (2~6 psi) = (2~6 psi) Typical Fine-Grained Soil Stress Softening Behavior

40. 0 4 8 12 16 20 24 28 024681012141618 APPLIED DEVIATOR STRESS  d (psi) RESILIENT MODULUS M R (ksi) A-4 soil at OMC A-4 soil at OMC+3 M R = - 2.21248  d + 29.696 R 2 = 0.9497 M R = - 0.6274  d + 1820 R 2 = 0.6617 M R = - 0.4203  d + 8.351 R 2 = 0.8715 M R = 0.0408  d + 4.9412 R 2 = 0.8796 Typical M R Characterization for Soils Bilinear or ArithmeticModel Greensboro, NC Airport Subgrade Soils

41. M R (psi) = 1500 * CBR (Heukelom and Klomp, 1962) M R (psi) = 2555 * CBR 0.64 (2002 Design Guide Prepared for AASHTO) Limited application for up to CBR = 10-12 Empirical M R - CBR Correlations

42. Greensboro, NC Airport Subgrade Soils Empirical M R - CBR Correlations The empirical correlations may not always work !..

43. PERMANENT DEFORMATION BEHAVIOR

44. Permanent Deformation Load Repetitions Wheel Rutting!.. Permanent Deformation – Rutting PRIMARY PERFORMANCE INDICATOR Base/Subbase Materials and Subgrade Soils Permanent Deformation:  p

45. Permanent Deformation Testing  Much less advanced than resilient behavior  No well-established test procedure exists  Yet, soil performance is solely judged by its field permanent deformation or rutting potential  Cohesive Soils – U of I procedure  Stress Levels: 25, 50, 75 & 100% of Q u  Subgrade Stress Ratio (SSR) =  D /Q u  N = 1000 (Conditioning) up to 100,000  For a given stress level  Permanent strain  p ) is monitored   p versus N plots for various stress levels

46. 0.00 0.02 0.04 0.06 0.08 0.10 1101001000 No. of Load Applications Permanent Strain,  p 1.00 SSR 0.75 0.50 0.25 Dupont Clay q u = 28 psi = 28 psi  d = 98 pcf = 98 pcf w = 26 % = 26 % Typical  p Test Results - Soils

47. 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.000.250.500.751.00 Subgrade Stress Ratio Perm. Strain after N=1000 moisturecontents 23.0% 26.0% 28.5% 30.5% Typical  p Test Results - Soils Dupont Clay

48. Primary Factors Applied stress states,  d,  3, and strength (Q u or  max )Applied stress states,  d,  3, and strength (Q u or  max ) –Subgrade Stress Ratio, SSR ( =  d / Q u ) Number of Load cycles, NNumber of Load cycles, N Secondary Factors – soil properties Moisture content, w (or Saturation, S R, %)Moisture content, w (or Saturation, S R, %) –Suction = f(depth to groundwater table) Plasticity index, PI and clay content, % (<2  m)Plasticity index, PI and clay content, % (<2  m) Dry density,  dDry density,  d Freeze-thaw effectsFreeze-thaw effects Factors Affecting Permanent Deformation  p of Soils

49. 0.001 0.01 0.1 1101001000 23.00%26.00%28.50%30.50% Dupont Clay  p =AN B Permanent Deformation - Power Model Permanent Strain,  p No. of Load Applications moisture contents

50. 1.E-05 1.E-04 1.E-03 1101001000  d = 45 psi  3 = 15 psi  p = 1.4x10 -4 N 0.137 R 2 = 0.96 No. of Load Applications Permanent Deformation - Power Model Permanent Strain,  p Sand

51. Thank you for the Excellent the Excellent Pavement !.. Pavement !..