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www.intrans.iastate.edu
Evaluation of MASW and FWD Test for Measuring Multi-Layered Elastic Modulus of Chemically Stabilized Unpaved Roads
Cheng LiMajor Professors: Drs. Jeramy Ashlock and David White
Measuring the elastic modulus for each of the material layers of unpaved roads are important
• Evaluate performance and predict damage susceptibility.• Conduct mechanistic design for overlay or surface upgrade.
IOWA STATE UNIVERSITYCivil, Construction, and Environmental Engineering
(a)
(b)
(c)
The MASW test procedure: (a) data collection, (b) dispersion analysis, and (c) inversion
Falling weight deflectometer (FWD) test
• Kuab Model 150 2m FWD • Four impact loads: 6000, 9000, 12000, and 14000 lb.• Backcalculation method: combines the Boussinesq theory
and Odemark’s equivalent layer thickness assumption (AASHTO 1993).
(b)(a)
Surface conditions of an unpaved road test section: (a) prior to freezing and (b) post thawing
Multichannel analysis of surface waves (MASW) test
• A geophysical test method using wave propagation theory.• A phase-velocity and intercept-time scanning method for
dispersion analysis (Lin 2014).• A hybrid genetic-simulated annealing optimization
algorithm for improving inversion (Lin 2014).
In situ FWD measured deflection data were compared with theoretical calculated results
• KENLAYER software using theory of elastic layer systems (Huang 2004).
Conclusions• The FWD backcalculation method is reliable for determining
elastic modulus of two-layer unpaved road systems.• The MASW is capable of measuring the near-surface
material elastic modulus of unpaved roads. • The MASW measured elastic modulus values are higher than
the FWD measured results due to low testing strain levels.
A comparison of FWD measured and theoretical calculated surface deflections
References• AASHTO (1993). AASHTO guide for design of pavement structures 1993,
American Association of State Highway and Transportation Officials, Washington, D.C.
• Huang, Y. H. (2004). Pavement analysis and design, Pearson Education, Inc., Upper Saddle River, New Jersey.
• Lin, S. (2014). "Advancements in active surface wave methods: modeling, testing, and inversion." Doctor of Philosophy, Iowa State University, Ames, IA.
Comparisons of the MASW and FWD test results
As-constructed FWD and MASW backcalculated moduli for the test sections
The FWD and MASW test results conducted during curing and post-thawing period
A (a) photo of the FWD test device and (b) schematic of sensors setup
(a)
(b)
Distance from the Center of the Loading Plate (in.)0 12 24 36 48 60
Roa
dway
Sur
face
Def
lect
ion
(in.)
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
FWD Measured (6000 lb Load)FWD Measured (9000 lb Load)FWD Measured (12000 lb Load)FWD Measured (14000 lb Load)Calculated (Theory of Elasticity)
7-Day 20-Day 30-Day 171-Day
15% Fly Ash Section
EA
GG (k
si)
0
100
200
300
400
500
600
MASW TestFWD Test
ES
G (k
si)
0
5
10
15
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25
30
7-Day 18-Day 28-Day 169-Day
15% Fly Ash Section 6% Cement Section
Note: The FWD elastic moduli are calculated under 6000 lb applied load
EA
GG (k
si)
0
100
200
300
400
500
FWDMASW
Testing Point Locations
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
ES
G (k
si)
0
5
10
15
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Control Section 5% Bentonite15% Fly Ash 6% Cement
Note: The FWD elastic moduli are calculated under 6000 lb applied load