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Subgrade Soil Support and Stabilization. O’HARE Airport Modernization Research Project. Research Progress Presentation – January 12, 2006. Co-PIs: Erol Tutumluer Marshall R. Thompson RA: H.S. Brar. Introduction.

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slide1

Subgrade Soil Support

and Stabilization

O’HARE Airport Modernization Research Project

Research Progress Presentation – January 12, 2006

Co-PIs: Erol Tutumluer Marshall R. Thompson

RA: H.S. Brar

slide2

Introduction

  • The strength and performance of an airport pavement related to the structural design and the subgrade soil characteristics
  • This project provides testing and analysis to establish subgrade support and stabilization requirements for O’Hare airport pavements
slide3

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
slide4

Research Objectives

  • Consider pavement design inputs for subgrade support
      • Modulus of subgrade reaction, k
  • Consider/Establish subgrade support and stabilization requirements with respect to:
      • Need for subgrade stabilization
      • Selection of lime and other suitable admixture stabilization considerations
      • Stabilization depth
  • Estimate “subgrade support” for various combinations of subgrade stabilization treatments and prepared subgrade conditions
slide5

Progress Made In 2004-05

Technical Notes have been prepared and submitted to the OMP throughout the project duration to:

  • Establish the Best Demonstrated Available Technology (BDAT) for subgrade soil evaluation and stabilization
  • Communicate specific findings and recommendations to OMP
  • engineers
  • TN5: K-150 Considerations for RW 9-27
  • TN6: Subgrade Strength/Stiffness Evaluation
  • TN7: “Working Platform” Requirements for Pavement Construction
  • TN8: Subgrade Stability Manual (IDOT)
  • TM13: Moisture Limitations for Lime Stabilization
  • TN14: Admixture Stabilization (Lime Treatment of Subgrades)
slide6

Progress Made In 2004-05

Subgrade test sections constructed in the Fall of 2003 and the plate load tests conducted in August 2004 on these test sections indicated that 12-in. quicklime and lime kiln dust (LKD) stabilizations were satisfactory

      • Plate 3: 12-inch quicklime fine stabilization (40 lb/yd2) 
      • Plate 4: 12-inch lime kiln dust stabilization (40 lb/yd2)
  • For characterizing the treated subgrade, Dynamic Cone Penetrometer and Light-Weight Deflectometer tests were performed by OMP designated firms

It was decided not to construct any new field test sections for this purpose

slide7

Progress Made In 2004-05

  • Sampling of the R9L-27R stockpiled soils
      • Grain size distribution (including hydrometer)
      • Atterberg limits (LL and PL for PI)
      • PH value & carbonate content
  • Selecting & identifying representative soil samples
  • Characterizing the representative soil samples by conducting tests at the UIUC ATREL for
      • Moisture-Density-CBR
      • Resilient Modulus
      • Unconfined Compressive Strength
      • Lime Treatment Effectiveness
  • Final Report summarizing Laboratory Soil Test Program & Year 1 research activities / findings
slide8

Soil Sampling: Dec. 04 – Feb. 05

Everest Engineering - Soil sampling & testing from 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
slide11

Progress Made In 2004-05

  • June 2005 technical report prepared on the Laboratory Soil Test Program presented preliminary results of the virgin and lime-treated soil testing efforts at ATREL focused on determining moisture-density-CBR relationships, unconfined compressive strengths, and resilient modulus properties
  • The need for soil stabilization was established from these preliminary test results
  • A 5 % LKD treatment was considered a feasible stabilization choice for increasing the strength/ modulus of the North Runway 9L-27R subgrade soils
slide12

Progress Made In 2004-05

  • A conference paper was submitted & accepted for presentation and publication in the conference proceedings

“Characterizing Subgrade Soils and Establishing Treatment Needs for a New Runway at the Chicago’s O’Hare Airport”

by H.S. Brar, E. Tutumluer, M.R. Thompson, L. Gosain, and R. Anderson

2006 ASCE Airfield and Highway Pavement Specialty Conference, Atlanta, GA, April 30 – May 3, 2006

slide13

University of Illinois Laboratory Testing Program at ATREL

Advanced Transportation Research & Engineering Laboratory (ATREL)

slide14

Grouping of Soils at ATREL

Grouping done primarily according to % clay content!..

slide16

Test Specimen Preparation

Air Drying

Pulverizing

Mixing

slide17

Moisture-

Density-

CBR Results

CBR

(ASTM D1883)

Untreated

Proctor Compaction (ASTM D698, D1557)

slide18

Group 1 Results

Lime Source:

High Calcium

Lime Kiln Dust (LKD)

slide19

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

Lime Source:

High Calcium

Lime Kiln Dust

(LKD)

slide20

OMC=18.8 %

OMC=14.4 %

OMC=14.4 %

Group 3 Results

Lime Source:

High Calcium

Lime Kiln Dust

(LKD)

slide21

Group 4 Results

Lime Source:

High Calcium

Lime Kiln Dust

(LKD)

slide22

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

slide23

MR Tests – Soil Samples

Cylindrical specimens, 2 in. f by 4 in. high

Undisturbed soil samples – Shelby tube (f = 2.8, 4 in.)

slide24

Group 1 MR Test Results

LEDFAA (FAA-AC No. 150/5320-6D, 2004) requires MR input

Bilinear or

Arithmetic

Model

Eri

15 to 20 ksi

slide25

Eri

Group 2 MR Test Results

Bilinear or

Arithmetic

Model

15 to 20 ksi

slide26

Eri

Group 3 MR Test Results

Bilinear or

Arithmetic

Model

15 to 20 ksi

slide27

Group 4 MR Test Results

Bilinear or

Arithmetic

Model

Eri

15 to 20 ksi

slide28

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

slide30

Group 1 with 5% Lime

without

lime

Lime Source:

High Calcium

Lime Kiln Dust (LKD)

slide31

Group 4 with 5% Lime

without

lime

Lime Source:

High Calcium

Lime Kiln Dust (LKD)

slide32

Lime Reactivity

Lime Source:

High Calcium

Lime Kiln Dust (LKD)

slide34

Summary of Results (1)

Moisture Density CBR Tests:

  • Optimum moisture contents of the natural soils were always lower those of the same soils treated with 5% lime kiln dust (LKD)
  • Similarly, maximum dry densities were always higher for the natural soils without lime treatment
  • The unsoaked CBR values obtained from testing the compacted specimens tend to drop sharply after the optimum moisture contents for the soils without lime
  • The treated soils with 5% lime always gave much higher unsoaked CBR values than the natural soils with no lime
  • In general, the 5% lime treatment was effective for increasing sufficiently the strength of the North Runway 9L-37R subgrade soils tested
slide35

Summary of Results (2)

Resilient Modulus (MR) Tests:

  • MR decreased with increasing applied deviator stresses; typical stress-softening fine grained soil behavior
  • All soil groups tested at the OMC gave high MR values at 6 psi deviator stress, in the range of Eri = 15-20 ksi

Unconfined Compressive Strength Tests:

  • Large increases in unconfined compressive strengths observed for all groups when 5% lime was added
  • Lime reactivity (Qu lime treated - Qu natural) is greater than 50 psi for all the groups except for Group 1
  • Minimum lime treated Qu = 119 psi was recorded for Group 1 soils with the lowest clay contents & the least reactivity with lime
slide36

Recommendation

From the results of all tests performed, “Green Light” is given to the 5% lime kiln dust (LKD) treatment at the new North Runway 9L-27R of O’Hare International Airport

  • seems to be working quite well in increasing the soil strengths
  • the improvements are sufficient to serve as a stabilized subgrade zone and alleviate wet soil conditions
slide37

FY 06 Year 2 Project Tasks

Task 1:

Conduct additional soil-lime testing in the laboratory for soil samples with different lime percentages and lime sources

  • Establish subgrade support for various combinations of subgrade stabilization treatments and prepared subgrade conditions
  • The data will also be helpful for considering the thickness design of the shoulder flexible pavements
slide38

Admixture Types / Sources

  • Carmeuse (potential supplier)
    • South Chicago (dolomitic lime)
    • Buffington, IN (high calcium lime)
      • Buffington is the primary source and primarily
      • worked with in year 1
  • Lime types
    • Lime Kiln Dust (LKD)
    • Quicklime fines
slide42

350

Sample 1

Sample 2

300

Sample 3

250

200

Axial Stress, psi

150

100

50

0

0

1

2

3

4

Axial Strain, %

Group 2 with 3% BLKD

slide47

FY 06 Year 2 Project Tasks

Task 2:

Provide OMP with guidelines and support for monitoring field soil lime stabilization and construction of the 9L-27R subgrades

  • The research team will provide recommendations on the various field tests such as automated dynamic cone penetrometer, Clegg hammer, Light-Weight-Deflectometer, etc.
slide48

FY 06 Year 2 Project Tasks

Task 3:

Evaluate the 9L-27R runway/taxiway soil lime stabilization and modification for meeting the subgrade support (k-value) requirements

  • The research team will support the activities of OMP in the evaluation of completed lime stabilization
  • Project Staff will cooperate with the OMP Project – Field Validation of Constructed Subgrade and Pavement Layers in this effort
slide49

FY 06 Year 2 Project Tasks

Task 4:

Evaluate currently available geotechnical/subgrade data for the South airfield of the O’Hare International Airport with particular emphasis on the stockpiled soils

  • Advise on the soil sampling needs and if considered essential, develop recommendations for additional soil exploration/sampling activities
  • The need to construct additional subgrade treatment test sections will be considered
  • Provide non-routine laboratory testing, such as the resilient modulus test, for the soils obtained from drilling and sampling and recommend and conduct (as time and budget permit) a lime-treatment testing program
slide50

Project Schedule & 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
  • 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
  • Continue to work with OMP on current and future subgrade soil support and stabilization needs for all O’Hare runways/taxiways. This will be in the form of sustained support for working with OMP on subgrade soil support issues
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