Geocells

Sundeep IntiVivek Tandon

Need for Reinforcement

• Shortage of Good Quality Material

• Pavement Thickness Limitations

• Reduced Financial Resources

Geocells Used

Presto

Tenex

Laboratory Evaluation Plan (Soils)

• Two Subgrade Types• Good (4.5 ksi)• Poor (2.5 ksi)

• Three Base Types• Good (15 ksi)• Marginal (12 ksi)• Poor (5 ksi)

Laboratory Evaluation Plan (Thickness)

• Subgrade Thickness 24 in.

• Base Thickness 10 in.

• Geocell Height 3, 4, and 6 in.

• Cover Thickness (7, 6 and 4 in.)

• Two Loading Plate Types (10 and 12 in.)

Laboratory Evaluation Plan(Box Dimension and Instrumentation)

Subgrade

Geocell

Cover

c

Pressure Cells

LVDT (vertical deformation)

Strain Gages

Box Size 3’ by 4’ by 5’

Finite Element Modeling

Load

Geocell

Geocell + infill

Section view

Subgrade

Cover

Geocell + infill

Quarter Model

Typical Laboratory Test Results

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100

150

200

250

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5

10

15

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30

35

40

0 2000 4000 6000 8000 10000

Stre

ss (k

pa)

Stre

ss (p

si)

Cycles

Stress on subgrade (unreinforced section)

LoadingRest

No Geocell Geocell

Subgrade

Base(9 ksi)

Geocell

Base Cover (9 ksi)

Subgrade

4”

6”

10” Unreinforced compared with 6” Geocell and 4” Cover

8 psi (reduction)

The stress on subgrade due to unreinforced section is 35% more than reinforced section

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50

100

150

200

250

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35

40

0 5000 10000

Stre

ss (k

pa)

Stre

ss (p

si)

Cycles

Stress on subgrade (reinforced section)

8.5 psi (reduction)

Comparison Between Laboratory and Finite Element Results

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50

100

150

200

250

300

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0 5 10 15 20

Stre

ss (k

pa)

Stre

ss (p

si)

Cycles

Loading

0

50

100

150

200

250

300

0.0

5.0

10.0

15.0

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30.0

35.0

40.0

45.0

50.0

0 5 10 15 20

Stre

ss (k

pa)

Stre

ss (p

si)

Cycles

Loading

8.3 psi (reduction)

Subgrade

Base(9 ksi)

Geocell

Base Cover(9 ksi)

Subgrade

6”

4”

10” Unreinforced compared with 4” Geocell and 6” Cover No Geocell Geocell

Design Approach

• Back-calculation of Geocell Reinforced Layer using Stress Analysis Tool of FPS-21.

Geocell (? Ksi)

Base (3 ksi) Cover

Subgrade (4.5 ksi)

6”

4”

Subgrade (4.5 ksi)

Base (3 ksi)

Geocell Reinforced Unreinforced Base

31.10 psi

20.20 psi

Base (70 Ksi)

Base (3 ksi) Cover

Subgrade (4.5 ksi)

6”

4”

Equivalent Base Modulus

Design Using Equivalent Modulus- Paris District

Surface Treatment (200 KSI) 0.5"

Surface Treatment (200 KSI) 0.5" Surface Treatment (200 KSI) 0.5"

3"

FLEXIBLE BASE 30 KSI 12"FLEXIBLE BASE 30 KSI 6"

196"

GEOCELL BASE 48 KSI 4"

SUBGRADE 9 KSISUBGRADE 9 KSI

HMA 500 KSI

CEMENT STABILIZED BASE (100 KSI) 7"

HMA 500 KSI

200" 200" SUBGRADE 9 KSI

3"

3"

HMA 500 KSI

Lamar County, Paris District (2015 ADT 1450, 2037 ADT 2030)

Current Design Alternative 1 Alternative 2

HMA 500 KSI 2"HMA 500 KSI 2"

HMA 500 KSI 2"

GEOCELL BASE 48 KSI 4"

SUBGRADE 4.5 KSI 196"

FLEXIBLE BASE 40 KSI 12"

HMA 500 KSI 3"

SUBGRADE 6 KSI SUBGRADE 6 KSI SUBGRADE 6 KSI

CEMENT TREATED BASE 35 KSI

FLEXIBLE BASE 40 KSI

GEOCELL BASE 48 KSI

FLEXIBLE BASE 40 KSI

200"

20"

200"

10"

4"

196"

8"

10"

FLEXIBLE BASE 25 KSI

Current Design Alternative 1 Alternative 2 Alternative 3

Ellis County , Dallas District (2017 ADT 1700, 2037 ADT 2400)

Design Using Equivalent Modulus-Dallas District

Design Using Equivalent Modulus-Fort Worth District

4"

HMA 500 KSI

6"

4"

20"

CEMENT TREATED BASE 120 KSI

GEOCELL BASE 48 KSI

FLEXIBLE BASE 30 KSI 8"

CEMENT TREATED BASE 120 KSI

HMA 500 KSI 4"

6"

4"

HMA 500 KSI

Cement Treated 120 KSI 15"

SUBGRADE 4.5 KSI SUBGRADE 4.5 KSI200" 200"

SUBGRADE 4.5 KSI200"

FLEXIBLE BASE 30 KSI

Current Design Alternative 1 Alternative 2

Tarrant County, Fort Worth District (2010 ADT 22990, 2030 ADT 33220)

Life Cycle Cost Analysis (Paris)

Current Design Description Units Unit Price No of Lanes Thickness (in) Width (feet) Length (miles) Quantity (Yd.3) Total Cost

Surface Treatment (200 ksi) CY 115 2 0.5 12 1 196 $22,489 Hot Mix Asphalt (500 ksi) CY 115 2 3 12 1 1173 $134,933 Cement treated Base (100 ksi) CY 75 2 7 12 1 2738 $205,333 Subgrade (9 ksi) CY 2 2 200 12 1 78222 $156,444

Cost $519,199

Design With GeocellDescription Units Unit Price No of Lanes Thickness (in) Width (feet) Length (miles) Quantity (Yd.3) Total Cost

Surface Treatment (200 ksi) CY 115 2 0.5 12 1 196 $22,489Hot Mix Asphalt (500 ksi) CY 115 2 3 12 1 1173 $134,934Flexible Base (30 ksi) CY 52 2 6 12 1 2347 $122,027Geocell Base CY ? 2 4 12 1 1564 ?Subgrade (9 ksi) CY 2 2 196 12 1 76658 $153,316

Alternative Cost $410,276Difference Compared with Current Design $108,923

Geocell Cost Per Square Yard $8

Life Cycle Cost Analysis (Dallas)

Current Design Description Units Unit Price No of Lanes Thickness (in) Width (feet) Length (miles) Quantity (Yd.3) Total Cost

Hot Mix Asphalt (500 ksi) CY 115 2 2 11 1 717 $82,459 Flexible Base (40 ksi) CY 56 2 8 11 1 2868 $160,616 Cement treated Base (35 ksi) CY 60 2 10 11 1 3585 $215,111 Subgrade (6 ksi) CY 2 2 200 11 1 71704 $143,407

Cost $601,593

Design With GeocellDescription Units Unit Price No of Lanes Thickness (in) Width (feet) Length (miles) Quantity (Yd.3) Total Cost

Hot Mix Asphalt (500 ksi) CY 115 2 2 11 1 717 $82,459Flexible Base (30 ksi) CY 52 2 10 11 1 3585 $200,771Geocell Base CY ? 2 4 11 1 1434 ?Subgrade (4.5 ksi) CY 2 2 196 11 1 70270 $140,359

Alternative Cost $423,769Difference Compared with Current Design $177,824

Geocell Cost Per Square Yard $14

Site Selected for Implementation-Paris (Texas)

Pavement Sections

Instrumentation Unreinforced

Section

Instrumentation Reinforced

Section

Soil Removal

Installation Help

Geocell Spreading

Final Geocell Layout

Geocell Infill Process

Unreinforced Section

Reinforced Section

-90

-80

-70

-60

-50

-40

-30

-20

-10

0D1 D2 D3 D4 D5 D6 D7D

efle

ctio

n (m

ils)

Deflection of Spot 3

Non-Geocell

Geocell

-70

-60

-50

-40

-30

-20

-10

0D1 D2 D3 D4 D5 D6 D7

Def

lect

ion

(mils

)

Deflection of Spot 5

Non-Geocell

Geocell

10/11/2018

Conclusions

• Use of Geocell Reduced Stress on Top of Subgrade Layer

• Life Cycle Cost Analysis (LCCA) Suggests Lower Overall Cost of Construction

• Pavement Can be Designed with Lower Quality Base and Subgrade Material and Still Reduce Overall Thickness of Pavement System

• Sustainable Solution to Material Problem

Thanks TxDOT for the Support

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