Rapid Soil Stabilization Technologies

J.Kent Newman, PhD
2008-11-13
Engineer Research and Development Center; Joint Rapid Airfield Construction; Maricopa County DAQEM

Objective

To employ mats, soil stabilizers, fibers, geotextiles, etc… for rapidly constructing airfield facilities

  • Low logistical effort
  • Minimal stabilization         
  • Reduced cure/construction times
  • Weatherproofing/dust control
  • Repair

 

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Photo: Soil Improvement (with Heavy Equipment)

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Photo: Aircraft Parking

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Photo: Matting Systems

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Photo: ERDC HVS Test Facility, C-130 Wheel, 30,000 Lbs on 6” of Stabilized Soil

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Photo: Dust Control Application

 

APPROACH

 

  • Applied Research (6.2) – Development of promising technologies for soil stabilization
    • Polymer/Cement blends
    • Fiber/Cement blends
      • Synthetic
      • Wood/cellulose
    • Polyurethanes/Epoxies
      • Single and two-component mixtures
    • Cold-weather curing of cements
  • Demonstration Technology (6.3) - Utilize existing technology for military applications
    • Scale-up of polymer/cement and fiber/cement stabilization from laboratory to field
    • Testing of commercial mat systems for airfield applications

 

Products

 

  • Airfield Matting
    • Materials
    • Construction and design methodology
  • Dust Control
    • Materials
    • Application and Construction Methods
  • Soil Stabilization
    • Materials – Including Freeze-thaw areas
    • Aircraft Specific Thickness Design
    • Construction Methods

 

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Photo: Dust Control Application

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Photo: ERDC HVS Test Facility, c-130 Wheel, 30,000 Lbs on 6” of Stabilized Soil

Rapid Stabilization Work Unit Plan

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Table: Rapid Stabilization Work Unit Plan

 

Pertinent Work Units

 

  • C-17 Shear-Resistant Stabilizer Development – FY07 End
  • Dust Control Technologies – FY07 End
  • Stabilization of Thawing Soils – FY05 End
  • Rapid MOG Enhancement Technologies – Need Extension through FY06
  • Demonstration of Advanced Stabilizer Technologies (C-130) – FY05 End
  • Field Testing of Advanced Stabilizer Technology (C-17) – FY06 End
  • Evaluation of Structural Requirements for Stabilized Airfields – FY06 End
  • Maintenance and Repair of Stabilized Layers – FY06 End
  • Demonstration of C-17 Stabilization Technology – FY06 New Start

 

Accomplishments Thru FY04

 

  • Progress:
    • Tested Commercial Mat Types Over Different Soil Strengths
      • C-130 contingency weights
    • Rapid Soil Stabilizers
      • Fibers and fast-setting cements
      • Polymers and fast-setting cements
    • Improved Dust Abatement
      • Best construction techniques
      • Best application equipment
      • Evaluated commercial products
    • Developed Cold Weather Stabilizers
      • Admixtures in cement for curing under freeze-thaw conditions
    • Ft. Bragg Demo

 

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Photo: Airfield Matting

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Photo: Soil Stabilization

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Photo: HUMVEE Sprayer

Ft. Bragg Demo – Mat testing for C-130 Loads

Test

Mat

6” Clay-Gravel Base (40-50 CBR)

Pressure Cell

Buckshot Clay 24” Subgrade (8-10 CBR)

Test

Mat

6” Base

Pressure Cell

Buckshot Clay 24” Subgrade (8-10 CBR)

Test

Mat

6” Base (3-5 CBR)

Pressure Cell

Buckshot Clay 12” Subgrade (8-10 CBR)

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Photo: 6” Clay Gravel Base

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Photo: Installing Pressure Cells at Top of Clay Subgrade

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Photo: C-130 Load Cart on Durabase

Ft. Bragg Demonstration – Materials

 

  • ACE Mat
    • Lightweight, easy to handle
    • Easy to install
    • Fiberglass
  • Polymers and Fibers - Why?
    • Reduced Logistics
      • Polymers and fibers weigh less than half of cement
    • Improved Performance
      • Less cracking means less FOD
  • Polymer/Cement Synergy
    • Polymer/fiber helps cement
    • Cement Helps polymer/fiber

 

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Table: Fort Bragg Soil Strengths

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Photo: Fibers

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Photo: Polymer

C-130 Load Testing of Stabilized Surfaces

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Photo: ERDC HVS Test Facility

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Graph: Rut Depth with Number of C-130 Wheel Passes

Ft. Bragg Demo Candidates – Testing

 

  • C-130 Wheel load 30,000 lb, 750 passes
  • One Day Cure
  • SM Soil

 

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Photo: Loaded C-130 Wheel on SM Soil

<Cracked at edge of wheel path, 5” rut>

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Photo: C-130 Testing on Emulsion Polymer/Cement

<Cracked at edge of wheel path, 3” rut>

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Photo: C-130 Testing on Fiber/Cement

<1/2” rut @ 750 passes>

Ft. Bragg Demo – C-130 Parking Aprons

 

  • Two C-130 Parking Aprons – 40,000 sq. ft. each
    • Apron 1
      • Half ACE mat
      • Half polymer/cement
    • Apron 2
      • Fiber/Cement

 

• Sicily ALZ, Ft. Bragg, NC

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Photo: Apron 1 – ACE Mat/Polymer/Cement

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Photo: Apron 2 – Fiber/Cement

FY05 Activities

 

  • C-17 Load Testing – Contingency loads at 206 kips/gear
    • Commercial Mats
      • Soloco Durabase – Heavy Duty
      • Soloco Bravo – Lightweight
      • ACE mat – Lightweight
    • Stabilized Soil
      • Fiber/Cement
      • Synthetic
      • Wood/Cellulose ?
  • Laboratory Testing
    • Moisture-Cure Polyurethanes
    • Different fiber types
      • Monofilament vs. fibrillated
      • Wood/cellulose
    • Improve fiber/soil/cement adhesion

 

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Photo: Test Facility

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Graph: Stress vs. Strain

MATS

 

  • What have we learned so far?
    • Durabase is an excellent load-bearing mat
      • Logistically unwieldy
      • Heat resistance?
    • Bravo mat suffered mechanical failure
    • ACE Mat is an excellent lightweight mat for medium strength (CBR >8) soils
      • 1000 passes of C-17 at contingency operating weight (206 kips) with minimal damage over CBR 8-10 SM soil
      • Needs proper anchoring for wind loads

 

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Photos: Various Mats

 

Soil Stabilization

 

  • Laboratory Testing of Soil Stabilizers
    • Moisture-Cure Polyurethanes
    • Different fiber types
      • Monofilament vs. fibrillated
      • Wood/cellulose
    • Improve fiber/soil/cement adhesion

 

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Photos: Laboratory Testing of Fiber Types

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Graphs: Stress vs. Strain

Moisture Cure Polyurethanes – MCPUR

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Graph: Unconfined Compressive Stress vs. MCPUR, 1% Soil Moisture

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Graph: Unconfined Compressive Stress vs. MCPUR, 5% Soil Moisture

Moisture Cure Polyurethanes – MCPUR

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Graph: Toughness vs. MCPUR, 1% Soil Moisture

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Graph: Toughness vs. MCPUR, 5% Soil Moisture

MCPUR Cure Time - UCS

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Graph: Unconfined Compressive Stress vs. Cure Time (Days) 

MCPUR Cure Time - TOUGHNESS

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Graph: Toughness vs. Cure Time (Days)

So Why not MCPUR?

  • Advantages
    • Super stress and strain properties
    • Would be great with added fibers
  • Disadvantages
    • Hard to construct with
    • Viscosity like honey
    • Sticks to equipment
    • Difficult to clean
    • Very expensive
    • Poor shelf life
    • Hazardous

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Photos: Application Equipment

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Photo: Aircraft/Airfield 

Effects of Cement and Fibers on Soil

  • Stress/Strain Response – ¾” Fibers

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Graph: Stress/Strain Response, Load Lbs. vs. In.

Effects of Fiber Type and Concentration

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Graph: Unconfined Compressive Stress vs. Stabilizer Type

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Graph: Toughness vs. Stabilizer Type

 

Soil Stabilization

  • What have we learned so far?
    • Cement is hard to beat - Economical, ubiquitous, easy to use
      • FOD nightmare when it fails
    • Fibers are excellent in blends with binders such as polymers and cements
      • Fibers reduce cracking – less FOD
      • Too long and fibers are hard to construct with
    • Emulsion polymers are easy to use
      • Great for weatherproofing, dustproofing surfaces
      • Don’t perform as well as fibers in blends with cement
      • Slow to cure without ‘help’ (cement)
    • Fibers
      • Improving adhesion of fiber to cement/soil is beneficial- ongoing research
    • Curing Polymers - Epoxies/polyurethanes
      • Single Component Moisture Cure Polyurethanes (MCPUR)
      • Great Properties
      • Hard to control, construct with
      • Two-Component Polyurethanes/Epoxies
      • Great Properties
      • Strict mixing requirements – special equipment needed
      • Can be controlled better than MCPUR

FY06-07 Activities

  • FY06 – C-17 Loads
    • Field Studies
      • Soil Stabilization
      • SM Soil 6” Depth, CBR 8-10
        • Synthetic Fiber/Cement Blends
        • Wood/Cellulose/Cement Blends
      • Clay Soil
        • Candidate materials will be based on laboratory studies
      • Maintenance and repair will be accomplished during field studies
      • Mat testing over Clays
    • Laboratory Studies
      • Stabilization of Clay Soil
      • Cement, lime, fibers, ionic stabilizers
  • FY07 – C-17 Demonstration
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