Re-Evaluation of Current TxDOT PVR Procedure with A New - - PowerPoint PPT Presentation

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Re-Evaluation of Current TxDOT PVR Procedure with A New Suction-Based Approach Rifat Bulut, Ph.D. Texas Transportation Institute Texas A&M University System Foundation Performance Association Houston, Texas August 10, 2005 TxDOT Project

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SLIDE 1

Re-Evaluation of Current TxDOT PVR Procedure with A New Suction-Based Approach

Rifat Bulut, Ph.D. Texas Transportation Institute Texas A&M University System

Foundation Performance Association Houston, Texas August 10, 2005

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SLIDE 2

TxDOT Project Background (2002-2004)

TTI Project Name: Design Procedure for Pavements on Expansive Soils (3 Volumes)

  • Volume I – Theoretical Background
  • Volume II – Experimental Protocols,

Case Studies Site Descriptions

  • Volume III – Computer Programs Manuals

PI:

  • Dr. Robert L. Lytton

Co-PI:

  • Dr. Charles P. Aubeny
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SLIDE 3

Outline

  • TxDOT PVR Assumptions
  • Analysis Program (Flodef)
  • Design Program (Winpres)
  • Laboratory Testing (Diffusion Coefficient)
  • TxDOT Case Studies
  • PVR Comparison
  • Implementation
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SLIDE 4

TxDOT PVR Tex-124-E Assumptions

  • Soil at all depths has access to water in

capillary moisture conditions

  • Vertical swelling strain is one-third of the

volume change at all depths

  • Remolded and compacted soils adequately

represent soils in the field

  • PVR of 0.5 inch produces unsatisfactory riding

quality

  • Volume change can be predicted by use of the

plasticity index alone

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SLIDE 5

Analysis Program - Flodef

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SLIDE 6

Analysis Program - Flodef

Two-Dimensional Transient Analysis For the Effects of:

  • Vertical Moisture Barrier
  • Subgrade Material (Lime Stabilized / Inert Soil)
  • Median Condition (Paved / Non-Paved)
  • Shoulder Condition (Paved / Bare)
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SLIDE 7

Analysis Program - Flodef

  • 2D Cross Section
  • Soil Index Properties
  • Geographic Location
  • Vegetation
  • Moisture Controls
  • Drainage Conditions

Input Output

  • Shrink-Swell versus Time
  • Suction versus Time
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SLIDE 8

Analysis Program - Flodef

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SLIDE 9

Analysis Program - Flodef

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Analysis Program - Flodef

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SLIDE 11

Analysis Program - Flodef

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SLIDE 12

Analysis Program - Flodef

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SLIDE 13

Analysis Program - Flodef

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Analysis Program - Flodef

Vertical Displacement of Outer Wheel Path, Fort Worth Section C ,Initial Wet

  • 3
  • 2.5
  • 2
  • 1.5
  • 1
  • 0.5

200 400 600 800 1000 1200 1400 1600 1800 2000

Time ( Days) Vertical Displacement( cm, +: swelling;-: shrinkage)

Natural Subgrade Vertical Barrier 2 ft

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SLIDE 15

Analysis Program - Flodef

Vertical Displacement of Outer Wheel Path, Fort Worth Section A/B, Initial Wet

  • 3.5
  • 3
  • 2.5
  • 2
  • 1.5
  • 1
  • 0.5

200 400 600 800 1000 1200 1400 1600 1800 2000 Time (Days) Vertical Displacement (cm, +: Swelling, -: Shrinkage) Natural Subgrade Inert Soil 2 ft

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SLIDE 16

Design Program - Winpres

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SLIDE 17

Design Program - Winpres

Input

  • Soil Index Properties
  • Geographic Location
  • Site Drainage and Vegetation
  • Pavement Data
  • Moisture Controls
  • Traffic Data
  • Reliability Level

Output

  • Shrink-Swell versus Time
  • PSI versus Time
  • IRI versus Time
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SLIDE 18

Design Program - Winpres

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SLIDE 19

Design Program - Winpres

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SLIDE 20

Design Program - Winpres

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SLIDE 21

Design Program - Winpres

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SLIDE 22

Design Program - Winpres

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SLIDE 23

Design Program - Winpres

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SLIDE 24

Design Program - Winpres

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SLIDE 25

Design Program - Winpres

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SLIDE 26

Design Program - Winpres

2.0 2.5 3.0 3.5 4.0 4.5 5 10 15 20 25 30 Time (yrs) Serviceability Index (SI) SN 4.00 in, Barrier 8.0 ft SN 4.14 in, LTS 1.8 ft SN 4.40 in, LTS 2.0 ft Flexible Pavement FWD 10000 psi ACP 4.0 in Reliability 50 % ADT (T= 0) 42,850 ADT (T=30) 67,950 W18 8,415,520

PSI versus Time

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SLIDE 27

Design Program - Winpres

60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 5 10 15 20 25 30 Time (yrs) International Roughness Index (IRI) (in/miles) SN 5.06 in, ACP 4.0 in, LTS 2.5 ft, Inert 2.5 ft SN 5.28 in, ACP 4.5 in, LTS 2.5 ft, Inert 1.5 ft SN 5.50 in, ACP 5.0 in, LTS 2.5 ft, Inert 1.5 ft SN 5.72 in, ACP 4.0 in, LTS 3.0 ft, Inert 1.5 ft Flexible Pavement FWD 10,000 psi Reliability 90 % ADT (T= 0) 42,850 ADT (T=30) 67,950 W18 8,415,520

IRI versus Time

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SLIDE 28

Laboratory Testing–Diffusion Coefficient

Apparatus

  • Thermocouple Psychrometers
  • Sling Psychrometer
  • Temperature Control Unit
  • A drill-bit, knife, spatula, tape, sealing

material (aluminum foil, plastic wrap, etc.)

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SLIDE 29

Laboratory Testing–Diffusion Coefficient

Laboratory Diffusion Test Setup

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SLIDE 30

Laboratory Testing–Diffusion Coefficient

Temperature Control System

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SLIDE 31

Laboratory Testing–Diffusion Coefficient

Thermocouple Psychrometer

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SLIDE 32

Laboratory Testing–Diffusion Coefficient

Psychrometer Calibration Solutions

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SLIDE 33

Laboratory Testing–Diffusion Coefficient

Thermocouple Psychrometer: S.N.43311

y = 1.4318x - 1.8953 R2 = 0.9976 Note: 1 bar = 100 kPa = 1019.8 cm pF = log(cm H2O) 10 20 30 40 50 60 5 10 15 20 25 30 35 40 45 Microvolt, µV Total Suction, bar

Osmotic Suction (bar) Linear (Osmotic Suction (bar))

Psychrometer Calibration Curve

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SLIDE 34

Laboratory Testing–Diffusion Coefficient

Sling Psychrometer

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Laboratory Testing–Diffusion Coefficient

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SLIDE 36

Laboratory Testing–Diffusion Coefficient

CR 7 Datalogger

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SLIDE 37

Laboratory Testing–Diffusion Coefficient

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SLIDE 38

Laboratory Testing–Diffusion Coefficient

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SLIDE 39

Laboratory Testing–Diffusion Coefficient

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SLIDE 40

Laboratory Testing–Diffusion Coefficient

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SLIDE 41

Laboratory Testing–Diffusion Coefficient

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SLIDE 42

Laboratory Testing–Diffusion Coefficient

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SLIDE 43

Laboratory Testing–Diffusion Coefficient

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SLIDE 44

Laboratory Testing–Diffusion Coefficient

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SLIDE 45

Laboratory Testing–Diffusion Coefficient

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SLIDE 46

Laboratory Testing–Diffusion Coefficient

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SLIDE 47

Laboratory Testing–Diffusion Coefficient

Diffusion Coefficient for BHC 2

3 3.5 4 4.5 5 5.5 6 100 1000 10000 100000 Drying Time (minutes) Suction, u (pF)

L = 15.93 cm x = 14.23 cm ua = 5.91 pF u0 = 3.51 pF he = 0.54 cm-1 α = 0.001 cm2/min

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SLIDE 48

Laboratory Testing–Summary

Suction Measurements

Thermocouple Psychrometer Filter Paper Method

Diffusion Coefficient Atterberg Limits # 200 Sieve

  • 2 micron (Hydrometer Test)
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SLIDE 49

TxDOT Case Studies

  • Fort Worth District
  • Atlanta District
  • Austin District
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SLIDE 50

TxDOT Case Studies

Fort Worth District - North Loop 820

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SLIDE 51

TxDOT Case Studies

Atlanta District - US 271

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SLIDE 52

TxDOT Case Studies

Austin - Loop 360

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SLIDE 53

TxDOT Case Studies

Index Properties

  • Atterberg Limits
  • Clay Fraction (Hydrometer analysis)
  • Fines Fraction (Wet Sieve)

Suction

  • Initial
  • Matric
  • Water Content-Suction Curve

Moisture Diffusion Coefficient

  • Diffusion Test

From filter paper test

}

(From filter paper test and pressure plate apparatus)

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SLIDE 54

TxDOT Case Studies

Sample No. Sample Depth (m) Liquid Limit (%) Plasticity Index (%) Percent Fines (%) Initial Total Suction (log kPa) Atmospheric Total Suction (log kPa) Laboratory Measurements αintact (cm2/sec) 1(A1) 3.35-3.66 45 22 84.2 2.38 5.06 5.90E-05 2(A5) 0.91-1.22 49 30

  • 2.02

5.21 7.86E-05 3(B2) 3.35-3.66 53 32

  • 2.30

4.93 9.66E-05 4(A1) 1.52-1.68 37 17 83.5 1.84 5.06 4.83E-05 5(C2) 2.74-3.35 37 15 89.9 2.43 4.76 13.1E-05 6(B1) 0.61-1.07 33 19 76.5 2.45 4.84 10.6E-05 7(B3) 2.89-3.35 50 29 95.9 2.77 4.76 4.66E-05

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SLIDE 55

TxDOT Case Studies

Sample No. Sample Depth (m) Liquid Limit (%) Plasticity Index (%) Percent Fines (%) Initial Total Suction (log kPa) Laboratory Measurements αintact (cm2/sec) Field Estimates αfield (cm2/sec) 1(A3) 2.74-3.04 63 43 93.6 2.25 5.05E-05 3.67E-03 2(B4) 3.96-4.26 45 21 99.4 2.56 1.08E-05 3.90E-03 3(C1) 0.61-0.91 62 36 99.7 2.28 3.73E-05 3.49E-03 4(C5) 2.13-2.43 42 19 98.2 2.81 1.73E-05 4.01E-03 5(B1) 1.07-1.52 47 29 75.3 2.53 5.65E-05 4.11E-03 6(B2) 1.98-2.43 68 48 91.8 2.39 6.30E-05 3.69E-03 7(B2) 2.89-3.26 68 48 90.6 2.21 1.07E-04 3.82E-03 8(B3) 1.07-1.52 49 29 84.9 2.46 3.21E-05 4.05E-03

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SLIDE 56

Subgrade Movements for the Pavement Design with Minimum Acceptable Predicted Performance, Austin, Loop 1

Movements at the Edge of Pavement (in) Movements in outer Wheel Path (in) PVR (in) Swell Shrink Tot Total Edge Outer+ Flexible ACP 4.0 in LTS 2.8 ft 0.78 0.66 1.44 0.93 2.40 1.93 Rigid CRCP 12.0 in LTS 2.0 ft 1.03 0.76 1.79 1.19 2.54 2.10 Flexible ACP 4.0 in LTS 2.0 ft I nert 2.0 ft 0.71 0.54 1.25 0.93 2.08 1.76 Rigid CRCP 11.0 in 2.03 1.00 3.03 2.28 2.97 2.37 Frontage Road Main Lanes Case Study Location Type of Pavemen t Acceptable Pavement Design*

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SLIDE 57

Summary

  • Total movement controls the rate of

increase in roughness

  • Shrink prediction alerts the designer

to longitudinal cracking

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SLIDE 58

Summary of Comparisons

PVR:

  • Over-predicts swell
  • Neglects shrink
  • Overly conservative designs
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SLIDE 59

IMPLEMENTATION

Three TxDOT Laboratories:

  • Dallas-Fort Worth
  • Austin
  • Bryan
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SLIDE 60

IMPLEMENTATION

Laboratory Testing Equipment

  • Filter Paper Method
  • Thermocouple Psychrometer
  • Transistor Psychrometer

Training Courses

  • Computer Programs
  • Analysis and Design
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SLIDE 61

ACKNOWLEDGEMENTS!

  • Dr. Robert L. Lytton
  • Dr. Charles P. Aubeny
  • Ms. Xiaoyan Long
  • Mr. Gyeong T. Hong
  • Ms. Eeshani Sood
  • Mr. Anshuman Thakur

and

  • TxDOT
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SLIDE 62

THANK YOU!

Rifat Bulut, Ph.D. Texas Transportation Institute Texas A&M University System (r-bulut@tamu.edu) (rifat.bulut@gmail.com)