effect of matric suction on resilient modulus of compacted recycled pavement material
DESCRIPTION
Effect of Matric Suction on Resilient Modulus of Compacted Recycled Pavement Material. Kongrat Nokkaew (Presenter) James M. Tinjum , Tuncer B. Edil. Research Motivations. Recycled pavement m aterial (RPM) crushed asphalt surface mixed with underlying base course - PowerPoint PPT PresentationTRANSCRIPT
Effect of Matric Suction on Resilient Modulus of Compacted Recycled Pavement Material
Kongrat Nokkaew (Presenter) James M. Tinjum, Tuncer B. Edil
Mid-Continent Transportation Research Symposium 2013
Research Motivations
Recycled pavement material (RPM) crushed asphalt surface mixed with underlying base course (i.e. subgrade and subbase)
Advantages Excellent mechanical properties (e.g. high modulus, low moisture susceptibility) Life-cycle benefit
(e.g. low transportation needs, no landfill cost) Environment-friendly
(reducing green house gas emissions, energy and natural aggregate consumption)
Mid-Continent Transportation Research Symposium 2013 Slide No. 2University of Wisconsin-Madison
Premature failure due to moisture in base layer
Base course: Moisture increases, modulus decreases Few studies on modulus-moisture for RPM
Mid-Continent Transportation Research Symposium 2013 Slide No. 3University of Wisconsin-Madison
Mid-Continent Transportation Research Symposium 2013 Slide No. 4University of Wisconsin-Madison
Unsaturated Zone
Saturated ZoneGround water table
βPavements are compacted near optimum water content unsaturated, and place above the ground water table. As a result, Pavement are unsaturated most of service lifeβ
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Soil-Water Characteristic Curves (SWCC)
Soil Suction in log scale
Volu
met
ric W
ater
Con
tent
(q)
ya
A relationship between soil suction and volumetric moisture content/degree of saturation
Matric Suction = negative pore water pressure (Ua β Uw)
ππ
ππ
Air entry pressure
Residual volumetric water content
Soil Particle
Menisci water
Mid-Continent Transportation Research Symposium 2013 Slide No. 6University of Wisconsin-Madison
Impact of moisture on Mr in the Mechanistic-Empirical Design Guide (M-EPDG)
Adjusting factor determined from degree at optimum degree of saturation
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Objectives
To evaluate the influence of matric suction on Mr for
compacted RPM in comparison to conventional crushed
limestone
To established a model for predicting Mr from matric suction
and the soil-water characteristic curve (SWCC)
To compare Mr from proposed model to those from M-EPDG
equation
r
drM
Where, d : deviatoric stress r : recoverable strain
Resilient modulus (Mr) Primary input for Mechanistic-Empirical Pavement Design Guide (M-EPDG) Impact to all quality and performance of pavement
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Background
Summary resilient modulus (SRM)
Mr representing stress state in the filed
SWCC fitting equation used in M-EPDG
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Ξ=πβππ
1βππ=[1β ππ(1+ π
π π )ππ(1+ 106
π π ) ][ 1
{ππ [π+ (Ο /a )π] }π ]
where = effective degree of saturation = degree of saturation;
= residual degree of saturation; is soil suction; , , , and are
fitting parameters; and is the base of the natural logarithm
Mid-Continent Transportation Research Symposium 2013 Slide No. 10University of Wisconsin-Madison
SWCC parameters estimated by the M-EPDG equation
πΌ=0.8627 π60
β 0.751
6.895n=7.5
π=0.1772 πππ60+0.7734 ππ
πΌ = 1π60+9.7πβ 4
SWCC parameter estimated based on d60
Parameter n: fixed at 7.5
where d60 is particle size in mm at percent finer 60%
Materials
0
20
40
60
80
100
0.010.1110100
RPM-MILimestone-WI
Per
cent
Fin
er (%
)
Particle Size (mm)
Properties RPM-MI Limestone-WI
USCS designation GW GP-GMAASHTO designation A-1-b A-1-a
Unit weight (kN/m3) 20.3 20.2
Water content (opt) (%) 6.4 8.1Percent absorption 1.7 2.5
Basic properties and soil Classification
Grain size distributions
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Limestone-WIRPM-MI
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MethodsHanging column test
Large-scale testing cell (305 mm x 76 mm)
Hanging column(y, 0.05 - 25 kPa)
Vacuum aspirator(y, 25 - 80 kPa)
Large-scale testing cell Matric suction:
Hanging column (y, 0.05 to 25 kPa) Air aspirator (y, 25 to 80 kPa)
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Outflow Reading
Air Aspirator1 kPa to 75 kPa
Bottom Platenwith Ceramic Plate
Water Pressure Transducer
Air Pressure Transducer
Latex membrane
Internal LVDT
External LVDT
Permeable Geotextile
Plunger
Mr test with suction control
Specimen
Modified Bottom Platen-with ceramic plate
Test performed according to NCHRP 1-37A Procedure Ia
Mid-Continent Transportation Research Symposium 2013 Slide No. 14University of Wisconsin-Madison
Mr test with suction control (Cont.β)
Outflow Column
Material preparation: Type I material (150 mm in diameters and 305 mm in height) Prepared at optimum wn and 95% of rd (modified Proctor effort)
Suction conditioningy supplied by vacuum aspirator y verification by checking the equilibrium outflow water
Sample saturation: To remove residual suction from sample compaction Assumed to be saturated when K is constant and outflow
is more than 3 pore volume of flow (PVF)
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π π=π1ππ( π+ππππ )π2(ππππ‘
ππ+1)
π3
Proposed resilient modulus model
Mr prediction for unsaturated base course (Liang et al. 2008)
where , , = fitting parameters; = matric suction;
= atmospheric pressure (101 kPa); = bulk stress;
and = octahedral shear stress; is Bishopβs effective stress
parameter
π=( ππ
π’πβπ’π€)
0.55
(Khalili and Khabbaz 1998)
Log y
S
Proposed resilient modulus model (Cont.β)
π π=π1ππ( π+Ξπ ππ
ππ)π2
(ππππ‘
ππ+1)
π3
assumed that
where = effective degree of saturation = fitting parameter;
= degree of saturation; = residual degree of saturation
π=Ξπ =(πβππ
1βππ)π
For summary resilient modulus ( = 208 kPa and = 48.6 kPa).
ππ π=ππ΄( 208+π©π πππ
)ππ΅
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(Vanapalli and Fredlund 2000)
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SWCC of studied material fitted with Fredlund andXing (1994) Model
Results
0
0.2
0.4
0.6
0.8
1
0.01 0.1 1 10 100 1000
Deg
ree
of S
atur
atio
n (S
)
Matric Suction (kPa)
M-EPDG Prediction
RPM-MI
Limestone-WI
RPM-MI (R2 = 0.96)
Limestone-WI (R2 = 0.98) Unimodal SWCC for RPM-MI, bimodal
SWCC for Limestone-WI
ya < 1kPa
SWCC predicted from M-EPDG:
Low ya (< 0.6 kPa)
Rapidly drop of slope when y > ya
Low yr (> 10 kPa)
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0
100
200
300
400
500
0 0.2 0.4 0.6 0.8 1
RPM-MI
Limestone-WIS
RM
(MPa
)
Degree of Saturation
Relationship between degree of saturation and Mr
SRM decrease as degree of saturation increase
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R2 = 0.90RPM-MI
SRM versus matric suction
0
100
200
300
400
500
600
1 10 100
RPM_MIProposed ModelLiang et al. (2008)
SR
M (M
Pa)
Matric Suction (kPa)
kA
= 3.44, kB =15.35, = 1.92
Proposed model: R2 = 0.90
Liang et al. (20): R2 = 0.88
0
100
200
300
400
500
600
1 10 100
Limestone-WIProposed ModelLiang et al. (2008)
SR
M (M
Pa)
Matric Suction (kPa)
kA
= 0.1, kB =19.28, = 0.49
Proposed model: R2 = 0.65
Liang et al. (20): R2 = 0.63
Tested at y = 1.5 kPa, 10 kPa, 20 kPa, 40 kPa, and 65 kPa
RPM-MI: SRM 216 β 290 MPa
Limestone-WI:SRM 75 β 191 MPa
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0
200
400
600
800
0.1 1 10 100
RPM-MILimestone-WI
SR
M (M
Pa)
Matric Suction (kPa)
ya
yr
a = -0.31; = 0.30, ks = 6.81
SRMopt
of RPM-MI = 358.3 MPa
SRMopt
of Limestone-WI = 173.7 MPa91 MPa (Saturated)
333 MPa (Residual Wn)
185 MPa
688 MPa
SRM versus matric suction fitted to the M-EPDG prediction
Change as y corresponding to SWCC Start to increase rapidly
when y > ya
Tend to constant when y > ya
SRMres/`SRMsat = 3.7 (both materials)
SRMM-EPDG/`SRMmeasured:
1.9 β 2.9 for RPM-MI 1.7 β 4.2 for DGA-WI
SRM predicted from the M-EPDG Equation:
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0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800
Proposed ModelLiang 2008MEPDG
Pro
pred
icte
d S
RM
(MP
a)
Measured SRM (MPa)
Proposed Model: R2 = 0.93
Liang et al. (2008): R2 = 0.93
1:1 Line
Comparison between predicted versus measured SRM using proposed model in comparison to Liang et al. (2008) and M-EPDG Equation
Variation of measured and predicted SRM
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Conclusions
RPM-MI provides higher SRM than limestone-WI
SRM increases as matric suction increase
The proposed model fits the test results well (R2 = 0.93)
over the full range of studied suction
SRMs predicted from M-EPDG are not conservative during
measured range of y (1 β 100 kPa)
Liang, R.Y., Rababβah, H., and Khasawneh, M. Predicting Moisture-Dependent Resilient Modulus of Cohesive Soils Using Soil Suction Concept. Journal of Transportation Engineering, Vol. 134, No. 1, 2008, pp. 34-40.
Vanapalli, S.K., and Fredlund, D.G. Comparison of Different Procedures to Predict Unsaturated Soil Shear Strength. Proc., of Sessions of Geo-Denver 2000, Advances in Unsaturated Geotechnics, ASCE, Reston, VA, 195-209.
Guide for Mechnistic-Empirical Design for New and Rehabilitated Pavement Structure. Final Report, 2004, NCHRP Project 1-37-A. www.trb.org/mepdg/guide.html. Accessed July 23, 2013.
Khalili, N., and Khabbaz, M.H. A Unique Relationship for for the Determination of the Shear Strength of Unsaturated Soils. Geotechnique, Vol. 48. No. 5, 1998, pp. 681-687.
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References
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Acknowledgements James Tinjum (Advisor) Tuncer Edil (Dissertation Committee) William Likos (Dissertation Committee) Benjamin Tanko (Undergraduate Assistant) The Solid Waste Research Program (UW-Madison) Recycled Materials Resource Center-3rd Generations The Royal Thai Government GeoFriends
Especically Xiadong Wang, Mababa Diagne, Ryan Shedivy
and Jiannan Chen
Questions ?