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IMPACT DEFLECTOMETRY IN THE STRUCTURAL EVALUATION,
CENTRAL HIGHWAY KM 12 + 250 - KM 26 + 500, LIMA 2020
Carlos Abner Julca Vásquez
Graduate University School - EUPG - Federico Villarreal National University, (Perú).
E-mail: carlos.julcav@gmail.com ORCID: https://orcid.org/0000-0002-2817-9079
Vicenta Tafur Anzualdo
Graduate University School - EUPG - Federico Villarreal National University, (Perú).
E-mail: itafur@unfv.edu.pe ORCID: https://orcid.org/0000-0002-1888-7848
Doris Esenarro
Graduate University School - EUPG - Federico Villarreal National University, (Perú).
E-mail: desenarro@unfv.edu.pe ORCID: https://orcid.org/0000-0002-7186-9614
Recepción:
5/03/2021
Aceptación:
4/06/2021
Publicación:
14/06/2021
Citación sugerida:
Julca, C. A., Tafur, V., y Esenarro, D. (2021). Impact deectometry in the structural evaluation, Central Highway km
12 + 250 - km 26 + 500, Lima 2020. 3C Tecnología. Glosas de innovación aplicadas a la pyme, 10(2), 95-115. https://doi.
org/10.17993/3ctecno/2021.v10n2e38.95-115
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ABSTRACT
This research analyzes the incidence and eciency of impact deectometry to evaluate and design the
road reinforcements of a section of the central highway. For this study, a "non-destructive" methodology
has been used, based on the collection, processing, and interpretation of the deections measured on
the road surface with the impact deectometer equipment; these deections reect a response of the
structural package under a given load, its measurement is simple, fast and "non-destructive," that is, we
do not alter the structural package, and above all, we do not cause vehicular congestion as it would be with
the conventional methodology. The deections are analyzed using the back-calculation technique, which
allows us to know the total Structural Number in the function of the characteristics of rigid pavement,
obtaining a structural number Sn of 6.2 and 5.6 for the right and left the roadway, respectively. This
research presents the results of the current condition of the road under study. It proposes a technique for
calculating the Structural Number of an asphalt reinforcement on concrete from the back-calculation.
KEYWORDS
Deection, Deectometry, Non-Destructive, Structural Package, Structural Number, Reinforcement.
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1. INTRODUCTION
Within the international context of the standards applied for the analysis and evaluation required
to determine the structural condition of road pavement, applying the so-called destructive and non-
destructive methods or tests stands out.
It is considered that measuring the condition of an existing pavement requires the application of
destructive processes on the road, which altered the balance of the pavement-subgrade system.
However, through new technologies or state-of-the-art instruments that apply high-performance testing
techniques, known as Non-Destructive Testing (NDT), roadway monitoring has improved (Alderete &
Brizuela, 2014). Among these techniques, the use of the Falling Weight Deectometer (FWD), whose
function is to analyze the structural condition of pavements by interpreting the deections produced
under dynamic loads that simulate the eect of trac, stands out. Another characteristic of the non-
destructive evaluation methodology is that since the "test sample" is the pavement itself, it represents the
true reection of the complex interaction between its components (layers of materials and subgrade),
and this "sample" can be tested at any time during its life without disturbing or destroying it.
The use of the impact deectometer generates a deection basin which represents the response of the
structural package due to the application of a load which is produced by vehicular trac so that the
deection can be correlated with the structural capacity of pavement so that if the deection is high
in a structural model, the structural power of the pavement model is weak or decient. Conversely, if
the deection is low, it means that the structural model of the pavement has good structural capacity.
With the help of back-calculation, it is possible to determine the pavement modulus used to calculate
the pavement's structural capacity (Andrade et al., 2015). Therefore, the back-calculation methodology
(also called retro analysis) is a tool that is currently considered the most appropriate for the structural
evaluation of pavements, which allows the determination of the modulus of the layers that compose it
and of the subgrade based on the knowledge of the thicknesses and the initial modulus.
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Currently, in Peru, the alternative of evaluating the structural capacity utilizing the study of deections
in concrete and asphalt pavement using the impact deectometer is little known.
1.1. LITERATURE REVIEW
Impact Deectometry
Impact Deectometry is a technology that allows evaluating the in-situ resilient modulus of pavement
and its component layers. This information is obtained by applying a dynamic load to the coating to
assess and record its deformation through sensors.
Impact Deectometer
The impact deectometer generates a deection basin. The characterization of the basin determines a
series of parameters that allow calculating the capacity of the subgrade of a pavement structure. Impact
tests are widely used to determine the subgrade strength with the Falling Weight Deectometer (FWD);
since they are non-destructive, they are a precious and fast technology, which, when adequately applied,
provides a wealth of information at a very reasonable cost and time.
It is provided with a variable number of geophones located at dierent distances from the load application
point, allowing for the deection basin. Due to its characteristics are used in the non-destructive
structural evaluation of already paved roads, generally when analyzing their rehabilitation requirements
with reinforcement layers. This use justies its high value since with an FWD, measurements can be
made continuously along several kilometers per day, being constantly moved to dierent sections under
analysis (Smith et al., 2017).
Structural Evaluation
The structural evaluation of pavements consists of determining the bearing capacity of the pavement-
subgrade system in an existing road structure. The back-calculation methodology (also called retro-
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analysis) is a tool that is currently considered the most appropriate for the structural evaluation of
pavements (Ávila et al., 2015).
2. METHOD
2.1. SITE ANALYSIS
The investigation was carried out on Route PE-22 - Emp. Lima - Chosica (Ricardo Palma Bridge) -
Matucana - Morococha, located between kilometers 12+250 to 26+500, where Santa Clara - Chaclacayo
is located.
It has a total length of 28.50 km as the section under study is made up of two carriageways, and each
carriageway has 2 to 3 lanes.
Figure 1. Geographical location of the section under study.
Source: own elaboration.
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Figure 1 shows the specic location of the section of the central highway under study, where the starting
point km 12+250 with coordinates (294768; 8671131) at an altitude of 417 masl and the endpoint at km
26+500 with coordinates (308077; 8675700) at the height of 671 masl (Homan & Thompson, 1981).
2.2. CHARACTERISTICS OF THE STUDY AREA
Climate and Meteorology
The climate is warm and temperate between Santa Clara and Chaclacayo with an average of 26.7°C,
January is the warmest month, and the lowest average temperatures of the year occur in June when it is
around 17.5°C. The climate in the area is hot and temperate. They have a signicant amount of rainfall
during the year, with averages of 1364 mm (Méndez et al., 2020).
2.3. MATERIALS
The evaluation of asphalt reinforcement on exible pavements using the FWD follows a methodology
proposed in the AASHTO 93 guide. Still, the mounts on a mixed pavement (concrete slab with asphalt
overlay) as is the case of the Central Highway from km 12+250 to km 26+500 would not be possible
to apply directly due to the type of rigid structure, so a methodology is proposed to determine the
Structural Number from the back-calculation parameters for the model of a rigid pavement (King &
Roesler, 2014).
For calculating concrete slabs, Homan and Thompson (1981) developed a method to transform the
deection data obtained from FWD tests of exible pavement into a deection basin area known as
AREA (1). This term, dened as AREA36, is calculated from normalized surface deections measured
0-in. (d0), 12-in. (d12), 24-in. (d24), and 36-in. (d36) oset from the center of the loaded plate (0, 30.5,
61.0 and 91.4 cm, respectively) (Alderete & Brizuela, 2014).
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FWD Impact Deectometer
The equipment used for the measurement of deections in the asphalt binder sections was the FWD
KUAB 150 impact deectometer (Figure 2), a dynamically loaded device coupled to a trailer, which is
transported by a van that meets all the requirements standardized by ASTM D 4694-96 and the SHRP
calibration protocol for this type of equipment. The deections produced are measured by a group of
seven (7) seismometers spaced every 0.30 m, allowing to obtain the complete curve of the deection
basin (William, 2014).
The results obtained for the deections are reported in the corresponding annex, where the deections
measured by the group of seismometers which are located at distances of 0, 0.30, 0.60, 0.90, 1.20, 1.50,
and 1.80 m from the center of the load disk are recorded; the temperature and the impact application
load are also shown.
Figure 2. Impact deectometer KUAB - 150 coupled to a trailer transported by a pickup truck, this device is dynamically loaded
and meets ASTM D 4694-96 requirements.
Source: own elaboration.
A B
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FWD Measurement Procedure
The measurement of deections in the pavement structure was performed on May 6 to 10, 2019,
alternately on the right and left lane of the roadway, every two hundred meters lane, equivalent to one
hundred meters roadway ten (10) points per kilometer (Ávila et al., 2020).
The test was carried out by applying a load of approximately 50 KN on the pavement; three (3) blows
or measurements were made at each measurement point to ensure the repeatability of the results within
an acceptable deviation range. The distance traveled by the equipment is registered by an odometer
that indicates the location of the point to be measured. The FWD has an infrared thermometer that
automatically registers the pavement surface temperature at each measurement point (Ministerio de
Transportes y Comunicaciones, 2013).
Figure 3. Inspection data collection.
Source: own elaboration.
Figure 3 shows the personnel in charge of data collection with the Impact Deectometer KUAB 150;
once the reading is done, the FWD equipment advances to its next data collection point.
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Structural Parameters
The structural capacity of a typical rigid pavement (without load transfer bars) and without other
additional layers is mainly given by the slab thickness (D), the Elastic Modulus of Concrete (EC), and
the Modulus of Subgrade Reaction (k). To know the thickness of the asphalt overlay, the slab thickness
has been cored, and therefore retro analysis allows determining EC and k from the FWD measurements.
Retroanalysis in rigid pavements is based on obtaining two basic parameters of the deection basin
(Figure 3): maximum deection and basin area.
Figure 5. Deection Basin.
Source: own elaboration.
• Maximum deection: Corresponds to the deection measured by the sensor located under the
load plate (d0)
• AREA: It is an indicator that considers the shape of the basin when incorporating more distant
deections, and in the case of rigid pavements, it is calculated as:
(1)
Where:
d₀= Maximum deection under load plate
d₁₂, d₂₄, d₃₆= Deection at 12, 24 and 36 inches from load plate
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On the other hand, both EC and k are related to each other according to the elastic theory developed
by Westergard in rigid pavements (Westergard, 1939) using a parameter called relative stiness (Lk)
according to the following relationship:
(2)
For the development of retro analysis in rigid pavements, it was determined that there is a relationship
between the relative stiness (Lk) and the AREA parameter:
(3)
Once determined (Lk), the value of k can be obtained according to the deection equation developed
by Westergard for rigid pavements:
(4)
Where:
P: Load in pounds
a: Load plate radius, inches
γ: Euler's constant, 0.57721566490
Finally, with the values of lK and k, the modulus of elasticity Ec of the concrete pavement can be cleared
from relation (2) (Homan & Thompson, 1981).
In case the model is used to evaluate asphalt overlays on concrete pavements, AASHTO considers that
the original deection basin must be corrected in its maximum deection due to the local compression
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eect that occurs in the asphalt layer when it is supported on a rigid layer (d0compress) according to the
following relation for bonded overlays:
(5)
Where:
D
ac: Thickness of asphalt overlay, in.
E
ac: modulus of elasticity of asphalt concrete, psi
The elastic modulus is determined as a function of temperature according to the following simplied
relationship proposed in AASHTO for the particular loading frequency conditions of FWD from a more
general relationship developed by Witczak for the Asphalt Institute.
(6)
Where:
T
p: Floor temperature, °F
Once the maximum deection has been corrected for the eect of localized compression, the ratios
developed by AASHTO for retro analysis in rigid pavements can be applied directly (Ubalde et al., 2020).
3. RESULTS
3.1. HOMOGENEOUS SECTORS
To establish working sectors with similar behavior and characteristics that facilitate the determination
of the design parameters per section in the road section, the cumulative dierence analysis method was
used.
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(7)
Where:
At: Sum of the cumulative area values obtained.
L: Length of the section under study (km)
3.2. DEFLEXION CHARACTERISTICS
After nding the homogeneous sectors and according to the road type classication, which refers to Table
12. 22 of the Roads Manual, Soils and Pavements section of the MTC, the characteristic deection is
calculated using the statistical factor 1.645 at reliability of 95% corresponding to the rst-class roads.
(8)
Where:
Dc: Characteristic Deection.
Dm: Mean Deection.
ds: Standard Deviation
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Figure 4. Calculation of deections CZD.
Source: own elaboration
Figure 4 and Figure 5 show the deection readings of the right and left the roadway, respectively. The
calculation of the average deection Do and the characteristic deection Dc, calculated by equation
(8) (right road = 222.6, left road = 353.9), is a fundamental parameter in the structural evaluation of
pavements (Esenarro et al., 2021).
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Figure 5. Calculation of deections CZI.
Source: own elaboration.
3.3. ESTIMATE OF THE STRUCTURAL NUMBER
In the present investigation, the maximum deection must be corrected because we are dealing
with asphalt overlays on a mixed pavement (concrete slab with asphalt overlay). Once the maximum
deection is xed for the eect of localized compression using the equation, the relationships developed
by AASHTO for retro analysis in rigid pavements can be applied directly. Obtaining the bowl area from
the deection area as a function of the maximum deection and the deections at 12, 24, and 36 in.
we calculate the relative stiness using equations (1 and 3). We obtain the eective Modulus K using
equation (4) with the calculated area and relative stiness (Homan & Thompson, 1981).
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For the calculation of the Eective Structural Number (SN), we use back-calculation parameters with
the following expression:
(9)
Where:
SN: Eective Structural Number.
d₀: Deection at Center, in mm
K: Modulus of reaction of the subgrade, in Mpa
Now the modulus of subgrade reaction according to Hogg's model for a mixed pavement is calculated
with the following equation:
(10)
Where:
K: Modulus of subgrade reaction, in Mpa.
R: Resistance value Hvenn (R-value of the subgrade)
To determine the Hvenn resistance value, the method relies on the following expression developed by the
Washington Department of Transportation.
(11)
Where:
R: Hvenn's Resistance Value of the Subgrade.
Mr: Resilient modulus of the subgrade, in KSI
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Figure 6. CZD Structural Number.
Source: own elaboration
Figure 6 and Figure 7 show the calculation of the Structural Number for the right and left the roadway,
respectively, using equations (9,10, and 11) where the average SN = 6.2 for the proper street and SN =
5.6 for the left road are also observed (Smith et al., 2017).
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Figure 7. CZI Structural Number.
Source: own elaboration
Table 1. Structural parameters.
SECTION ROADWAY
CONCRETE
SLAB
THICKNESS
ASPHALT
LAYER
THICKNESS
EAC k
static
MODULUS
OF
ELASTICITY
Ec
STRUCTURAL
NUMBER
(cm) (pulg) (psi) (pci) (psi) SN
Km 12+250
a
km 26+500
Right 26.2 3.7 661,061.2 241.6 33,701.3 6.2
Left 20.0 3.4 704,625.0 266.0 28,661.3 5.6
Source: own elaboration
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Table 1 shows the average thicknesses of the asphalt overlay and the existing concrete slab. These were
obtained by taking core samples and calculating the structural parameters of the modulus of elasticity of
the asphalt and concrete, static K-modulus, and the structural number (Andrade et al., 2015).
4. CONCLUSIONS
The test was performed by applying a load of approximately 50 KN, generating three (3) blows in each
of the test points to know the behavior of the evaluated structure. The spacing between tests is 100 m.
To determine the thicknesses of the existing structural package (asphalt coating and concrete slab), core
samples were extracted.
The Structural Number obtained for the proper roadway is SN = 6.2 and for the left road is SN = 5.6.
With the information of the deection basin obtained with the impact deectometer, the structural
capacity of pavement in service can be calculated by means of the parameter called Structural Number
Sn.
The application of this methodology signicantly facilitates the controls and the structural evaluation of
the road reinforcements on mixed pavements with signicant advantages:
• No destructive evaluations.
• Reduction of time and ecient procedures to know the road reinforcement of a road.
REFERENCES
Alderete, N., & Brizuela, L. (2014). Diseño de pavimentos urbanos por retrocalculo según guía
AASHTO 93 mediante la utilización del deectómetro liviano de impacto. Infraestructura Vial,
16(27), 4–14. https://dialnet.unirioja.es/servlet/articulo?codigo=5051931
3C Tecnología. Glosas de innovación aplicadas a la pyme. ISSN: 2254 – 4143 Ed. 38 Vol. 10 N.º 2 Junio - Septiembre 2021
113
https://doi.org/10.17993/3ctecno/2021.v10n2e38.95-115
Andrade Neto, I. C., Andrade Neto, D. I. I., & Runo, D. I. J. (2015). Metodología de análisis de
la condición del pavimento a partir del cuenco de deexión. Infraestructura Vial, 17(29), 24–32.
https://doi.org/10.15517/iv.v17i29.15270
Ávila, E., Albarracín, F., & Bojorque, J. (2015). Evaluación de pavimentos en base a métodos no
destructivos y análisis inverso. Maskana, 6(1), 149–167. https://doi.org/10.18537/mskn.06.01.11
Avila, L. A., Esenarro, D., Rodriguez, C., Paredes, P., & Metzger, L. (2020) Application of
Pavement Index for the Evaluation of the Running Surface of the Lima-Peru Roads. Journal of
Green Engineering, 10(10), 8129-8141. https://siis.unmsm.edu.pe/es/publications/application-of-
pavement-index-for-the-evaluation-of-the-running-s
Esenarro, D., Martinez, R., Miranda, M., Begazo, L., & Segovia, E. (2021). Sustainable
Construction of Ancasmarka and Its Functionality in the Pre-Inca and Inca Period, Calca - Cusco
– Perú. Journal of Green Engineering (JGE), 11(2). http://www.jgenng.com/volume11-issue2.php
Homan, M. S., & Thompson, M. R. (1981). Mechanistic Interpretation of Nondestructive Pavement Testing
Deections. UILU-ENG-81-2010. University of Illinois at Urbana–Champaign. https://trid.trb.
org/view/169968
King, D., & Roesler, J. R. (2014). Backcalculation procedure for bonded concrete overlays of asphalt
pavement. Transportation Research Record, 2457(2), 72–79. https://doi.org/10.3141/2457-08
Martínez, W., & Moyano, C. A. (2014). Evaluación Estructural Del Pavimento En Las Plataformas Norte Y
Sur Del Aeropuerto Internacional El Dorado. Universidad Católica de Colombia. https://repository.
ucatolica.edu.co/bitstream/10983/2571/1/Evaluaci%C3%B3n-estructural-pavimento-
plataformas-norte-y-sur-El-Dorado.pdf
3C Tecnología. Glosas de innovación aplicadas a la pyme. ISSN: 2254 – 4143 Ed. 38 Vol. 10 N.º 2 Junio - Septiembre 2021
114
https://doi.org/10.17993/3ctecno/2021.v10n2e38.95-115
Méndez, R., Esenarro, D., Amaya, P., & Rodriguez, C. (2020). Vulnerability of the soils of
Metropolitan Lima and their relationship with urban sustainability. 3C Tecnología. Glosas de innovación
aplicadas a la pyme. Edición Especial, Octubre 2020, 161-177. https://doi.org/10.17993/3ctecno.2020.
specialissue6.137-147
Ministerio de Transportes y Comunicaciones. (2013). Manual de Carreteras- "Especicaciones Técnicas
Generales para la Construcción". Lima.
Smith, K. D., Bruinsma, J. E., Wade, M. J., Chatti, K., Vandenbossche, J. M., & Yu, H. T.
(2017). Using Falling Weight Deectometer Data with Mechanistic-Empirical Design and Analysis, Volume I:
Final Report. Report No. FHWA-HRT-16-009. Federal Highway Administration, I(March), Report
No. FHWA-HRT-16-009. https://www.fhwa.dot.gov/publications/research/infrastructure/
pavements/16009/16009.pdf
Ubalde, R., Rodriguez, C., Petrlik, I., Esenarro, D., Lezama, P., & Sotomayor, J. (2020). Quality
model for Peruvian microenterprises of a software product Factory. Test Engineering and Management,
83, 13434.
