40th International Symposium on Automation and Robotics in Construction (ISARC 2023)

Evaluation of ground stiffness using multiple accelerometerson the ground during compaction by vibratory rollers
Y.Tamaishi1,2，K.Fukuda2，K.Nakashima3，R.Maeda2，K.Matsumoto3，R.Kurazume3
2

1
Tamaishi Juki Co., Ltd., Japan
Graduate School of Information Science and Electrical Engineering, Kyushu University, Japan

3
Faculty of Information Science and Electrical Engineering, Kyushu University, Japantamaishi@irvs.ait.kyushu-u.ac.jp, k_fukuda@irvs.ait.kyushu-u.ac.jp, k_nakashima@irvs.ait.kyushu-u.ac.jp,
maeda@irvs.ait.kyushu-u.ac.jp, matsumoto@irvs.ait.kyushu-u.ac.jp, kurazume@ait.kyushu-u.ac.jp

Abstract –Soil compaction is one of the most important basic
elements in construction work because it directly
affects the quality of structures. Compaction work
using vibratory rollers is generally applied tostrengthen ground stiffness, and the method that
focuses on the number of compaction cycles is widelyused to manage the ground stiffness by vibratoryrollers. In contrast to this method, the continuouscompaction control (CCC) using accelerometers
installed on the vibratory rollers has been proposed
as a quantitative evaluation method more suited toactual ground conditions. This method quantifies the
distortion rate of the acceleration waveform of thevibratory roller. However, this method based on
acceleration response has problems in measurement
discrimination accuracy and sensor durability
because the accelerometer is installed on the vibrationroller, which is the source of vibration. In this paper,
we propose a new ground stiffness evaluation method
using multiple accelerometers installed on the groundsurface. The proposed method measures theacceleration response during compaction work by
vibratory rollers using multiple accelerometers on the
ground surface. Experiments show the proposed
method has a higher discrimination than theconventional methods.
Keywords –Vibratory rollers, Ground stiffness evaluation

1

Introduction

Vibratory rollers are used for compaction tostrengthen the ground stiffness. To manage the groundstiffness using vibratory rollers, the number ofcompaction cycles is widely used as a compaction work
management method.
In contrast, the continuous compaction control (CCC)
method utilizing acceleration response during262

compaction has been proposed as a quantitativeevaluation method that reflects actual ground conditions[1] [2] [3] [4] [5]. This method uses accelerometers
installed on a vibratory roller to quantitatively evaluatechanges in ground stiffness owing to compaction.
Performance was compared between CCC measurements
and location-specific in-situ test results. By including theeffect of moisture content using multivariate regression,
the consistency between the CCC and in situ test data sets
was higher than without inclusion [6].
This method uses the phenomenon in which theacceleration waveform of a vibratory roller is disturbed
as the stiffness of the compacted soil increases andquantifies the distortion rate of the waveform. Thisphenomenon is caused by the vibratory rollers bouncing
up and impacting against the stiffened ground.
However, this method based on acceleration response
has problems in terms of measurement discrimination
accuracy and sensor durability because accelerometers
are attached to the vibratory rollers that are the source ofvibration.
This paper proposes a ground stiffness evaluation
method with a higher discrimination than that in theconventional method using multiple accelerometers
installed on the ground surface to measure theacceleration response during compaction by a vibratoryroller.
In the experiment, the embankment was compactedusing a vibratory roller, and the acceleration signals of
the ground surface vibration were measured during
compaction using accelerometers installed on the ground(proposed) and on the vibratory roller (conventional).
The compaction control value (CCV) [7] was used as anindex to evaluate the ground stiffness. The CCV obtainedby the proposed method which utilizes the multiple
accelerometers on the ground was compared with theconventional CCV obtained by the accelerometer on thevibratory roller. In addition, the coefficient of the groundreaction force was measured using a light falling weightdeflectometer (LFWD) test and its relationship with the40th International Symposium on Automation and Robotics in Construction (ISARC 2023)

CCV obtained using the proposed method was also
verified.

Figure 1 shows the comparison image of theconventional method and the proposed method.

2

3

Background

CCC (or the acceleration response method) uses anacceleration sensor fixed to the main body of a vibratoryroller to estimate the degree of ground compaction fromthe acceleration waveform during the compaction
process. The phenomenon used in this method is thatwhen compaction by the vibratory roller progresses, aspectrum appears in the amplitude spectrum of theacceleration waveform at a frequency other than thefundamental frequency of the compaction by thevibratory roller.
This phenomenon is considered to be caused by avibratory roller bouncing up against a rigid ground andimpacting it [8]. CCC evaluates the ground stiffness by
calculating the spectral turbulence using the compaction
meter value (CMV) [1], the resonance meter value(RMV), CCV [5], etc., which calculates turbulence ratio
based on the ratio of the spectra at multiple vibration
frequencies. CCC can manage the compaction conditionin 2-dimensions by combining the obtained spectral
disturbance with the positional information obtained by
the GNSS installed on the vibratory roller.
However, this conventional method has a problem
with measurement discrimination accuracy, particularly
in soils with a high water content. In such cases, thespectral turbulence becomes unclear, and evaluating thedegree of compaction is often difficult. In addition,
because the accelerometer is installed at the vibration
source, the measured values contain a significant amountof noise. Furthermore, the proximity of the sensor to thevibration source can cause the sensor to malfunction.
The ground stiffness evaluation method proposed inthis study is similar, in that it is based on the amplitude
spectrum ratio of the acceleration waveforms. The
difference is that the multiple accelerometers are
installed on the ground. The installation of theaccelerometers on the ground reduces sensor failures andthe signal-to-noise ratio; this is expected to improve themeasurement discrimination accuracy.
Conventional method

Accelerometer

Proposed method

Accelerometers

Evaluation method

In this study, the ground stiffness during compaction
by a vibratory roller is evaluated by integrating thevibration data obtained from several distributed
accelerometers on the ground. The vibration data fromeach sensor are obtained as triaxial acceleration signals
corresponding to the operation of the vibratory roller.
The Z-axis is vertical to the ground, and the X-Y axis
is horizontal to the ground. This study uses only the XY-axis component that is stably obtained because the Zaxis signal is suppressed when the wheel of the vibratoryroller passes over the ground.
First, the short-time Fourier transform (STFT) is
applied to acceleration signals 𝑎𝑖,x , 𝑎𝑖,y in the X-Y axis at
the 𝑖 -th sensor (𝑖 = 1 … 𝑁) ( 𝑁 is the total number of
sensors) to obtain spectrogram 𝑆𝑖,𝑥 , 𝑆𝑖,𝑦 . Next, composite
spectrogram 𝑆̃𝑖 is calculated as follows:22+ 𝑆𝑖,𝑦𝑆̃𝑖 = √𝑆𝑖,𝑥(1)

As explained above, ground stiffness is estimatedusing the obtained composite spectrogram, 𝑆̃𝑖 . In theevaluation of ground stiffness based on the roller
acceleration response, the acceleration waveform is
known to be disturbed as the ground stiffness increases.
Unlike conventional methods that directly measureacceleration signals of the vibratory roller, which is a
vibration source, this study measures the acceleration
signals of vibrations propagating on the ground surface.
This method is expected to reduce the signal-to-noise
ratio. In this study, CCV [7], defined by the following
equation, is used as the ground stiffness index.
CCV(𝑆) =𝑠0′ + 𝑠1′ + 𝑠1 + 𝑠2′ + 𝑠2
× 100
𝑠0′ + 𝑠0(2)

denotesthefundamental
component𝑠0
corresponding to oscillation frequency of spectrogram 𝑆(the vibratory roller frequency), 𝑠𝑛 denotes the highfrequency component corresponding to 𝑛 + 1 times thefrequency, and 𝑠𝑛′ is the 1/2 fractional harmoniccomponent corresponding to 𝑛 + 0.5 times the frequency.
As the ground stiffness increases, high-frequency andfractional harmonic components dominate, and the CCV
increases owing to turbulence in the acceleration
waveform. Finally, the CCVs obtained from N sensors
are averaged.
𝑁

CCV =

Figure 1. Comparison image of the conventional
method and the proposed method

1∑ CCV(𝑆̃𝑖 )
𝑁
𝑖=1

263

(3)

40th International Symposium on Automation and Robotics in Construction (ISARC 2023)

4

Experiment

4.1

Experimental setup

In this study, an embankment was used as theexperimental environment. The ground rolling
experiment was conducted at an outdoor test site locatedon the Ito campus at Kyushu University. The experiment
was conducted using a vibration roller (SAKAI, SV512DV) and high-sensitivity 3-axis accelerometers (Onosokki,
NP-7310).
In the experiment, compaction and measurement
lanes were prepared on the embankment. Accelerometers
were placed at 5 m intervals at the top of the embankment,
and a vibratory roller ran along the compaction lane. The
compaction experiments were conducted on two layers(1st and 2nd layers). In the 1st layer, there were twocompaction lanes: the F-lane far from the accelerometers
and the N-lane close to them. Figure 2 shows thearrangement of the accelerometers and dimensions of theembankment on each layer, and Figure 3 shows theexperimental conditions. The experiments wereconducted as follows.

(2) The soil was rolled 12 times back and forth (24times in total) using a vibratory roller on themeasurement lane. After rolling the measurement lane,
four accelerometers were fixed to the ground surface ofthe measurement lane with stakes at intervals of 5 malong compaction lanes.
(3) Twelve round trips (24 times in total) of rolling by
the vibratory rollers were repeated on the compaction
lane, and the measured values of each accelerometer
were recorded.
(4) After removing accelerometers, a 0.3 m thick 2ndlayer of soil was spread on the former layer.
(5) The 2nd layer test was subjected to the sameprocedure (2) to (3) as the 1st layer to measureacceleration.
LFWD tests were conducted during compaction (2, 4,
6, 8, and 10 round trips) on each layer. In the LFWD test,
an impact load was applied by free-falling a weight on
the loading plate. The displacement caused by the impact
was measured at the center of the load and at the radial
position from the center of the load to obtain thecoefficient of the subgrade reaction [9].
𝐾P.FWD = (

𝑃X
𝐷Y1
)∙(
)
𝛿X
𝐷Y2

(4)

𝐾P.FWD ：Coefficient of subgrade reaction by LFWD
(MN/m3)
𝑃X ：Load stress at displacement X mm (MN/m3)
𝛿X ：Displacement X (mm)
𝐷Y1 , 𝐷Y2 ：Diameter of LFWD loading plate Y1 (cm),
Diameter of FWD loading plate Y2 (cm)4.2(a) 1st layer

Soil condition

Figure 4 shows the particle size distribution curve of
the fill material used in this experiment. The gravel
content was low, but the fine-grained (clay and silt)
content was high (> 50%), making the soil difficult tocompact. All uniformity coefficients were higher than 10,
and the grain size distribution was good. Table 1 shows
the result of particle component ratio.

(b) 2nd layer

Percent(%)
finer (%)

Figure 2. Arrangement of accelerometers

Figure 3. Experimental setup in the outdoor field(1) A 0.3 m thick layer of soil was spread onto a wellcompacted base. (1st layer)

264

100
Fine-grained90
content
80
70
60
50
40
30
20
10
0
0.001
0.01

0.1

1
(mm)
Particle size (mm)10Figure 4. Particle size distribution curve10040th International Symposium on Automation and Robotics in Construction (ISARC 2023)

Table 1 Particle component ratio
Parameters used forclassification
Coarse gravel %Medium gravel %Fine gravel %Coarse sand %Medium sand %Fine sand %Silt %
Clay %
Maximum grain sizemmCoefficient of
uniformity
Coefficient of curvature

Sample
No.1

No.2

No.3

2.4
11.3
9.6
0.5
8.4
16.4
42.1
9.3

3.9
10.1
9.9
25.2
12.6
9.8
23.1
5.6

8.0
8.4
9.2
0.2
4.3
18.7
43.5
7.7

26.5

37.5

53.0

30.0

104.2

21.5

0.8

0.5

0.8

4.3

Dry density (g/cm3)

The dry density versus moisture content curve for thesame fill material is shown in Figure 5. The samples used
for the measurements were prepared using the dry
method and were us ed in the repeat method. Table 2
presents the number of times the samples were rammed
and the other test parameters.

Natural moisture
content

Water content (%)

Figure 5. Moisture–density curve for fill materials
Table 2 Dry density versus moisture content test
conditions
Type of soil
Mass of rammer (kg)
Falling height (m)Number of times tampered
per layer
Number of layers tampered
Inner diameter of mold (m)Height of mold (m)Volume of mold (m3)
Maximum grain size (m)The results of the experiment on the samples from thethree sites showed that the average optimum moisture
content was approximately 10.9%, average maximum
dry density was approximately 1.96 g/cm3, and natural
moisture content at the time of the experiment wasapproximately 8.7%.

Decomposed granite
2.5
0.3
25
3
0.1
0.1273
0.001
0.019

265

Experimental results

Figure 6 shows the CCV. In each figure, the CCV foreach position on the forward journey (left), CCV for eachposition on the backward journey (center), and CCV rateof change averaged over the travel section (right) are also
shown. Results of N-lane on the 1st layer are shown in
Figure 6 (a), and 2nd layer are shown in Figure 6(b). In
these figures, #1 ~ #4 indicate the positions ofaccelerometers.
The CCV rate of change is defined as relative rate ofchange 𝑟𝑛 with respect to the CCV𝑛 at the 𝑛th time ofcompaction. The 𝑟𝑛 is calculated separately for each caseof forward and backward journey, thus 𝑛 is 3 ≤ 𝑛 ≤ 24
when determining the 𝑟𝑛 .
𝑟𝑛 =CCV𝑛 − CCV𝑛−2
CCV𝑛−2(5)

As shown in Figure 6, the CCV of the proposed
method increased with the number of compaction cycles,
showing a convergence trend on each layer. However, theCCV of the conventional method increased anddecreased irregularly and did not converge. This isconsidered to be owing to the reduction in the signal-tonoise ratio by the separation of the vibration source andthe measurement device that improves the convergenceand discrimination of the proposed method.
In addition, Figure 7 shows the relationship between
CCV and the number of compaction cycles when thevibratory roller passed at the position A on the N-lane andA′ (midway position, 7.5m) in Figure 2. The relationshipbetween the rate of change of CCV and the number ofcompaction cycles with same condition is also shown in
Figure 7.
The conventional method has a large variation in
CCV. The CCV increased when the number ofcompaction cycles was small, but decreased when thecompaction had progressed on each layer.
On the other hand, the CCV measured by the
proposed method tended to increase and converge as thenumber of compaction cycles increased. The CCV values
measured in the forward directions were larger than thosemeasured in the backward direction. It is possible that therear wheels block the vibrations propagating through theground when the rear wheels are ahead of the vibratory
wheels, but this should be verified in the future.

backward

CCV

30
20
10
0

0

4 8 12 16 20 24
Number of compactions
pa

200
160
120
80
40
0
-40
-80

forward0

backward

Proposed method

forwardRelative rate of change (%)

40

4 8 12 16 20 24
Number of compactions

Proposed method

Conventional method

The CCV rate of change varied widely with theconventional method and the trend was difficult to read,but with the proposed method, it decreased and showeda convergence trend on each layer.

Figure 8. CCVs evaluated on N-lane of the 1st layer oneach point

40

forward

CCV

30
20
10
0

4 8 12 16 20 24
Number of compactions

200
160
120
80
40
0
-40
-80

forward0

backward

4 8 12 16 20 24
Number of compactions

Proposed method0backward

Relative rate of change (%)(a) CCVs and 𝑟𝑛 evaluated on N-lane of the 1st layer
Conventional method

Conventional method

40th International Symposium on Automation and Robotics in Construction (ISARC 2023)

The results of this experiment were obtained underlimited soil conditions. It is well known that the change
of CCV tends to become unclear with increasing
moisture content [10]. A similar trend may be obtainedwith the proposed method, and this will be discussed in
the future.
To investigate the effect of the distance from theaccelerometers to the vibratory roller, an additional
experiment was conducted in which the vibratory roller
compacted the compaction lane on the far side (F-lane)
and more than 4 m away from the accelerometer.
Figure 9 shows the CCVs of the F-lane and N-lane.
Although the CCV is larger on N-lane than on F-lane,
the CCVs of both lanes clearly converge. This indicatesthat the proposed method is effective even when thevibration roller is more than 4 m away from theaccelerometer.

(b) CCVs(b)
CCVs andand 𝑟𝑛 evaluatedevaluated onon thethe 2nd
2nd layer
layer
Figure 7. CCVs and 𝑟𝑛 when the vibratory roller
passed at the positions A and A′ in Figure 2
Figure 8 shows the comparison of CCVs at three points(5m, 7.5m and 10m) on the N-lane of the 1st layer for theconventional and proposed methods. Compared to theconventional method, CCVs of the proposed method arestable and the convergence trend is clearly observed.

(a) F-lane on the 1st layer

Figure 9. CCVs for varying distance fromvibration source to accelerometers266

40th International Symposium on Automation and Robotics in Construction (ISARC 2023)

Figure 9. CCVs on F-lane and N-lane.
The resulting coefficients of the subgrade reaction(MN/m3) are listed in Table 3 and Table 4. The LFWD
test was conducted at the fourth, eighth, 12th, 16th, and20th of compaction on each layer. The heat map for thecase where the embankment traveled in the longitudinal
direction is shown in Figure 10.
Table 3 Coefficients of subgrade reaction on 1st layer
with LFWD. (MN/m3) (n = 24)
4th
118
155
88
15.4

Ave.
Max.
Min.
SD

8th
137
160
112
14.4

12th
139
180
118
14.7

16th
139
189
110
17.4

20th
155
210
112
23.5

Rate of change of coefficient(b) N-lane on the 1st layer

The results confirmed that the coefficients of thesubgrade reaction tended to increase as the number ofcompaction cycles increased.
The rate of change of the coefficients of the subgrade
reaction obtained by the LFWD was also calculated.
Because LFWD measurements were obtained at 4th, 8th,
12th, 16th, and 20th compaction, the unmeasured
coefficients of the subgrade reaction were linearlycomplemented, and the average rate of change wasobtained. Figure 11 shows the results and same
convergence trend as the CCV rate of change shown in
Figure 6.
Because the LFWD is measured over a long period oftime at the surface of the compacted ground, it is difficult
to measure at construction sites. The acceleration
response method proposed in this study can be measured
at a location off the compaction ground and is considered
to be useful at construction sites.

Table 4 Coefficients of subgrade reaction on 2nd layer
with LFWD. (MN/m3) (n = 11)
4th
119
133
109
8.7

Ave.
Max.
Min.
SD

8th
137
152
125
8.9

12th
155
189
139
15.9

16th
157
185
139
15.5

20th
163
187
113
21.5

2nd

4th

6th

8th

10th

(b) Coefficients of subgrade reaction on 2nd layer
Figure 10. Coefficients of subgrade reaction with LFWD

267

6%
4%
1st layer
2nd layer

2%
0%
-2%
-4%

0

4

8

12

16

20

24

Number of compations

Figure 11. Rate of change of coefficient ofsubgrade reaction with LFWD

4.4(a) Coefficients of subgrade reaction on 1st layer

8%

Simulation results

Simulations were conducted to find out thecharacteristics of the conventional and proposed methods.
The acceleration of the roller was varied so that the
impact amplitude between the roller and the groundincreased as the compaction cycles increased. In addition,a low-pass filter was applied to smooth the vibration as it
passed through the ground in the proposed method. Since
damping decreases as the stiffness of the groundincreased, it was assumed that the cutoff frequency
increased as the number of compaction cycles increased.
Figure 12 shows the CCVs when the impact
amplitude and the cutoff frequency of the low-pass filter
were increased in the conventional and proposed
methods, respectively. In both cases, the CCVs increase
when the impact amplitude or the cutoff frequency
increases. In particular, the proposed method showed anonlinear relationship between the cutoff frequency andthe CCVs. From this non-linearity, it is expected that the40th International Symposium on Automation and Robotics in Construction (ISARC 2023)

CCVs change gradually during initial compaction cycles.
On the other hand, the CCVs increase uniformly for any
compaction cycles for conventional method. This may
cause the different characteristics and may be one of thereasons why the proposed method has higher
discriminability than conventional method.

Acknowledgement
The authors are grateful to Prof. Yasuhiro Mitani andProf. Hisatoshi Taniguchi for technical assistance withthe experiments. This work was supported by the JST[Moonshot R&D] [Grant Number JPMJMS2032].

References

Impact amplitude(a) Conventional(a)Conventional method
methodCutoff frequency
Cutofffrequency(b) Proposed method

Figure 12. CCVs of conventional and proposed
method obtained by the simulation

4.5

Advantages and limitations

The experimental results suggest that the proposed
method is more discriminative than the conventional
method. The proposed method also shows superiority in
failure resistance and signal-to-noise ratio compared tothe conventional method.
On the other hand, the proposed method has
disadvantages compared to the conventional method interms of labor and cost required to install sensors. It isalso necessary to consider the effects of vibrations
generated by surrounding machinery. Furthermore, sinceabsolute values vary depending on the distance from theroller to the acceleration sensor, evaluation by absolutevalues are currently difficult and can only be compared
relatively. Further discussion on this issue is needed in
the future.

5

Conclusions

This paper proposes a method for evaluating groundstiffness using multiple synchronous acceleration sensors
placed on the ground. The proposed method is superior
to the conventional method in terms of discriminationand convergence with respect to the number ofcompaction cycles, as confirmed by ground rolling tests
on embankments. The convergence tendency of the
proposed method was similar to that of the coefficient of
the subgrade reaction calculated using LFWD.
In a future study, experiments will be conducted on
soils with various moisture contents to clarify thecharacteristics of the proposed method.

268[1] Thurner H. and Sandstrom A. A New Device for
Instant Compaction Control. In International
Conference on Compaction, Vol. II pages 611-614,
France, 1980.
[2] Forssblad L. Compaction Meter on Vibrating
Rollers for Improved Compaction Control. In
International Conference on Compaction, pages
541– 546, Paris, France, 1980.
[3] Adam D. Continuous Compaction Control withvibratory rollers. In Geo Environment 97, pages
245-250, Rotterdam, Netherlands, 1997.
[4] Adam D. and Brandl H. Sophisticated roller
integrated continuous compaction control. In 12th
Asian Regional Conference on Soil Mechanics andGeotechnical Engineering, Vol. 1 pages 427-430,
Singapore, 2003.
[5] R. Anderegg and K. Kaufmann. Intelligent
Compaction with Vibratory Rollers: Feedback
Control Systems in Automatic Compaction andCompaction Control. Journal of the Transportation
Research Board, 1868(1):124-134, 2004.
[6] Christopher M, Daniel C, Faraz T and William B.
Assessing soil compaction using continuouscompaction control and location-specific in situ
tests. Automation in Construction, 73:31-44, 2017.
[7] Sakai Heavy Industries, Ltd. Vibrating roller typesoil compaction quality controller CCV(compaction control value), Operating &Maintenance Instructions, pages 1-5, 2007.
[8] Hashimoto T. Fujino K. and Tateyama K.
Suggestion of the ground stiffness estimative
method with the running speed of a plate compactor.
In International Symposium on Automation andRobotics in Construction, pages 1-6, Alabama,
USA, 2016.
[9] UniversityofMarylandCollege
Park.
Standardizing lightweight deflectometer modulus
measurements for compaction quality assurance,
pages 5-8, Final report for Maryland Department ofTransportation State Highway Administration
Research Report, 2017.
[10] Wei H, Pawel P, Xiaoyang J, Hongren G and
Baoshan Huange. Visualization and quantificationof lab vibratory compacting process for T aggregatebase materials using accelerometer. Transportation
Geotechnics, 25:1-8, 2020.

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40th International Symposium on Automation and Robotics in Construction (ISARC 2023)

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Conventional method(a) CCVs and 𝑟𝑛 evaluated on N-lane of the 1st layer(b) CCVs and 𝑟𝑛 evaluated on the 2nd layer
Figure 6. CCVs and 𝑟𝑛 evaluated results ("#𝑛" denotes the position of the n-th accelerometer)269