geocells - texas a&m...
TRANSCRIPT
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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50
100
150
200
250
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5
10
15
20
25
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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10
15
20
25
30
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
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
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
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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