Sixth International Conferenc e on Geotechnique, Construction Materials andEnvironment, Bangkok, Thailand, Nov. 14-16, 2016, ISBN: 978-4-9905958-4-5 C3051

ANALYTICAL EVALUATION OF THE INFLUENCE OF HOLESFORMED BY PULLING OUT PILE FOUNDATIONS ON
THE MECHANICAL CHARACTERISTICS OF
THE SURROUNDING GROUND
Kazuki Nosho1, Shinya Inazumi2, Suttisak Soralump3, Shuuichi Kuwahara4 and Yusuke Torigoe51Advanced Course of Architecture and Civil Engineering, Akashi College, National Institute of Technology,Japan; 2Department of Civil Engineering, Akashi College, National Institute of Technology, Japan;
3
Department of Civil Engineering, Kasetsart University, Thailand; 4Marushinn Co., Ltd., Japan;
5Department of Earth Sciences, Okayama University, JapanABSTRACT

Teardowns of social infrastructure, including civil structures, have been increasing in number in recent years
because these structures have aged and their utilization has decreased along with the decrease in population. The
number pile foundations being pulled out is now far greater than that being newly installed. However, after a pilefoundation is pulled out, the mechanical characteristics of the surrounding ground may be affected by the existenceof the resulting hole formed by pulling out. There are no regulations yet on injecting fillers into pull-out holes, andthe influence of filler strength on the surrounding ground is yet to be elucidated. This study considers the influenceof a pull-out hole on the static and dynamic characteristics of the surrounding ground using two-dimensional
dynamic finite-element analysis. The special qualities required by fillers injected into such holes are also clarified.
Keywords: existing pile foundation, pull-out hole, surrounding ground, two-dimensional dynamic finite-element
analysis
as such materials cannot ensure reliable filling orstable strength, the use of processing soil and cement–
bentonite has increased in recent years. However,there are no regulations yet on the filler that are
injected into pull-out holes, and the influence of filler
strength on the surrounding ground is yet to beelucidated.
This study considers the influence of the pull-out
holes of pile foundations on the static and dynamic
characteristics of the surrounding grounds using twodimensional dynamic finite-element analysis. The
special qualities required by fillers for being injected
into pull-out holes are also clarified in this study.

INTRODUCTION
In Japan, many cities are located on soft ground,and many structures use pile foundations. Therefore,for land to be reutilised in places where existing
structures are present, it is necessary to remove theexisting piles supporting the structure as well as thestructure itself for construction of a new structure.
Further, existed piles and concrete husk become
industrial waste, be left of these industrial waste in theground is a very difficult problem. In addition, thepresence of such piles remaining in the ground is seen
as a hidden defect in land transactions [1].
Accordingly, it can be said that the removal ofexisting piles is essential.
Methods of removing existing piles include thepull-out method and the crushing-removal method [2].
The crushing-removal method suffers from vibration,
noise and environmental problems, and hence, thepull-out method is more widely used. However, thepull-out method also has certain problems; inparticular, a hole is formed when an existing pile ispulled out of the ground, and if this hole is leftunattended, it is possible that the ground surface may
subside as earth and sand collapse into the hole.
Therefore, it is necessary for filler to be injected into
the pull-out hole. Conventionally, mountain sand or
sand recycled from construction is used as filler, as
these materials are simple and inexpensive. However,

SUMMARY OF THE STUDY OF THE
DYNAMIC BEHAVIOUR OF THE PULL-OUT
HOLE AND THE ORIGINAL GROUND
The tasks involved in this study are described inpoints (1) to (5) (as shown in Fig. 1).
(1) Select the study cross section and the inputground-motion waveform.
(2) Create an analytical model based on the crosssection selected in point (1), and set the meshdivision of the analytical area.
(3) Select an analytical constant. Set the application
configuration model and material parameters in
the initial stress analysis and the dynamic total
129

GEOMATE- Bangkok, Nov. 14-16, 2016

START(1) Select the study cross section andthe input ground-motion waveform(2) Create an analytical model and mesh(3) Select an analytical constant(a) Empty pull-out hole(4) Perform the initial stress analysis.
(5) Perform dynamic total stress analysis

END
Fig. 1 Analytical procedurestress elastic–plastic analysis.
(4) Perform the initial stress analysis. The analysis
technique used is total stress analysis. In this study,
an HD model for the ground material and anelastic model for the hollow portion are applied.
(5) Took over the calculated ground in stress at 4 ,perform dynamic total stress analysis. Again, aswith the initial stress analysis, the HD model forthe ground material and the elastic model for thehollow portion are applied. Enter the seismic
acceleration at the bottom of the analytical model.

(b) Filled pull-out holeFig. 2 Sectional view

DYNAMIC BEHAVIOUR OF THE PULL-OUT
HOLE AND THE ORIGINAL GROUND, THE
ANALYTICAL MODEL AND THE INPUTGROUND-MOTION WAVEFORM(a) Empty pull-out holeAnalytical model
In the analysis, the analytical cross section has
two layers. The upper layer has clay as a soft stratum,
for which the N-value is approximately 4. The lower
layer consists of a strong formation of gravel serving
as a support layer, for which the N-value isapproximately 50. The width of the analytical crosssection is set at 50 m, the thickness of the clay layer
is 18 m, the thickness of the gravel layer is 8 m andthe total depth of the cross section is 26 m. Two pullout holes exist in the model at a spacing of 4 m; thepore diameter is 1 m, depth is 20 m and the depth ofembedment in the gravel layer is 2 m. To improve theaccuracy of the analysis, a finer mesh spacing is usednear the pull-out hole. This finer mesh continues to beused even when the pull-out holes are filled in order
to examine the behaviour of the filling. As a boundary(b) Filled pull-out holeFig. 3 Analytical model

condition, in the dynamic analysis, the bottom is a
fixed fulcrum and the lateral boundary is the equaldisplacement boundary. When the moving node on
the side of the left side, node of the other side to the130

GEOMATE- Bangkok, Nov. 14-16, 2016

γt represents the weight per unit volume of soil; γwrepresents the weight per unit volume of water; G0represents the initial shear stiffness; σ’m represents theinitial average active confining pressure; ν represents
Poisson’s ratio; c represents the adhesive force; φrepresents the internal friction angle; qu represents thecompressive strength; and E represents the elastic
coefficient.

Table 1 HD model parameters
Parameters
(kPa)
(kPa)
ν (-)
c (kPa)φ (°)

Clay layer
27900
900.45250

Gravel layer
298485
234
0.40
050

Input ground-motion waveform

Table 2 Elastic model parameters
Parameters
qu(N/mm2)
E (kN/m2)ν (-)

filler 1

Pull-out holes (filler)
filler 2
filler 3

0.1

0.5

1.025280
0.48

1264000.46252800
0.44

In the analysis, the waveform of the El Centro
1940 NS earthquake (which was provided by theBuilding Centre of Japan) is exerted on the substrate’ssurface. The maximum acceleration is 341.7 cm/s2.
ANALYTICAL RESULTS AND STUDY OF
THE DYNAMIC BEHAVIOUR OF THE PULLOUT HOLE AND THE ORIGINAL GROUND

Table 3 Element parameters
Parameters(kN/m3)(kN/m3)
Constitutivelaw

Clay layer

Gravellayer

Pull-out
holes(filler)

152115

The results of the dynamic analysis for the three
types of ground are shown as follows.
Results of the dynamic analysis

9.8
HD modelHD model

Figure 4 shows the diagrams of the maximum
displacement for each of the three ground types. Inaddition, Fig. 5 shows the X-direction displacement
contour diagrams, and Fig. 6 shows the Y-direction
displacement contour diagrams. Figure 7 shows thetime history view of the X-direction displacement of
the ground centre in the cases where no pull-out holes
are present and where the pull-out holes have been
filled.

Elastic
model

displacement is the same movement as the node on
the side of the left. Therefore, it is possible to express
whether the stratum has spread to the left or right.
Analysis is performed on three types of ground:
one with no pull-out holes, one with empty pull-out
holes and one where the pull-out holes are filled. The
analytical cross-sectional view of the ground is shownin Fig. 2. A similar analytical model is shown in Fig.
3. In the case of filled pull-out holes in Figure 3, theportion surrounded by a red frame is the pull-out holeportion. The parameters of the HD model in the clay
and gravel layers are shown in Table 1. Table 2 shows
the parameters of the elastic model of the pull-outhole.

Study of the results of the dynamic analysis
It can be seen that the ground wave causes
significant horizontal displacement in all cases when
it is allowed to act on the base surface. From Figure
4, it can be seen that a large ground subsidence occurs
in the vertical direction when the pull-out hole isempty. The maximum subsidence in ground surface
is approximately 60 cm, which is very dangerous.
However, this subsidence does not occur in the casewhere the pull-out holes are filled. Thus, it can be said
that filling the pull-out hole is an effective way toprevent subsidence.
From Fig. 4, it can be seen that, using filler 1, themaximum horizontal displacement is on the left side,
unlike in the other cases. Figure 5 clearly shows thatthe behaviour of the horizontal displacement underfiller 1 is different from that of the other cases.
In the other cases, displacement to the right occurs
rapidly at approximately 5 seconds and displacement
have continued while the displacement remained.
However, if the displacement at 5 seconds is small,

Constitutive law and material parameters
The parameters in the clay and gravel layers usedin the analysis as well as the soil parameters in thepull-out hole are shown in Table 3. In this analysis, afluidising processing soil is used as a filler;
experimental values of its properties can be seen in
the literature [3], [4]. In addition, three fillers withdifferent elastic moduli and different Poisson ratios
are analysed in order to examine the effect of filler
strength on the ground. The strengths of the fillers
increase in the order filler 1, filler 2, filler 3.
Parameters used in the analysis is to determine theanamnestic literature reference [5].
131GEOMATE- Bangkok, Nov. 14-16, 2016(a) No pull-out hole(c) Filler 1(b) Empty pull-out hole(d) Filler 2(e) Filler 3

Fig. 4 Displacement diagram (The amount of displacement is three times)(a) No pull-out hole(b) Filler 1(c) Filler 2(d) Filler 3
Fig. 5 X-direction displacement contour diagrams(a) No pull-out hole(b) Filler 1(c) Filler 2(d) Filler 3
Fig. 6 Y-direction displacement contour diagrams132

GEOMATE- Bangkok, Nov. 14-16, 2016(a) No pull-out hole(b) Filler 1(c) Filler 2(d) Filler 3

Fig. 7 Time history view of the X-direction displacement of the ground centre

portion and subsidence occurs on the right side when
fillers 2 and 3 are used. Furthermore, it can be seenthat the displacement increases as the filler strength
increases.
CONCLUSIONSIn this study, two-dimensional dynamic finiteelement analysis was used to elucidate the effect ofpull-out holes of foundation piles on the dynamic
behaviour of the ground.
The results obtained from the analysis are shownbelow.
(1) Ground subsidence occurs in the vicinity of a pullout hole when the hole is left empty, particularlyin the area sandwiched between two pull-out holes.
A very large subsidence occurs in a wide range ofground surfaces if ground motion is applied .
(2) When the pull-out holes are filled, groundsubsidence does not occur in the dynamic or static
analyses. For this reason, it is clear that filling
pull-out holes is effective.
(3) When the filling strength is too small relative tothe strength of the original ground, the groundmay behave in a significantly different way fromthe case with no pull-out holes. For this reason, it
is necessary to change the filler strength to suit theground conditions.
This study has not taken account of the influenceof different compounding filler materials or different
hole shapes. Therefore, there is a need to investigate
these conditions as the subject of future analysis.

Fig. 8 Graph comparing the horizontal displacements ofthe ground centre line

then the system will soon return to its original
configuration. From this fact, it is believed that thebehaviour of the horizontal displacement of theground varies greatly when the filling material
strength is too small. From Fig. 5, it can be seen thatthe horizontal displacement is greatest in the casewhere filler 3 is used and the displacement isapproximate in the case where no pull-out holes andfiller 2 are used. Figure 8 shows a comparison of thehorizontal displacements of the ground centre line.
From Fig. 8, it can be seen that rapid displacement of
the clay layer bottom occurs in all cases. In addition,
the behaviour of the ground with holes filled by filler
2 is considered to be closest to the behaviour of theground without pull-out holes. In the verticaldirection, bulging occurs on the left side of the filling
133

GEOMATE- Bangkok, Nov. 14-16, 2016

processing soil”, Summaries of Technical Papersof Annual Meeting Architectural Institute ofJapan, pp.591-592, 2014.
[4] Furugaki Y, “Deformation properties of thebackfill material which has a fluidity and selfhardening”,
TowN-value-up
Management
Report, No.37, pp.41-44, 2011.
[5] Ministry of Land, Infrastructure, Transport andTourism (MLIT), “Public Building Construction
Standard Specification (Building Work) 2013
Edition”, MLIT, 2014.

REFERENCES[1] Murakami T, “Leaving the foundation pile,backfilling denied the defects of ground support
force of the part, agent of accountability violation
was also negative case”, RETIO, No.82, pp.166167, 2011.
[2] Marushicn Co., Ltd., “About the PG Methods”,
http://marushinn.jp/about_chacking.html, 2016.
[3] Furugaki Y, Nakasawa F, Utaka Y, Tokuda K,“Study on the Young's modulus of the fluidized134