International Journal of GEOMATE, July, 2017, Vol. 13, Issue 35, pp. 16-21
Geotec., Const. Mat. & Env., ISSN:2186-2990, Japan, DOI: http://dx.doi.org/10.21660/2017.35.6544

INFLUENCE OF PULLING OUT EXISTING PILES ON THE
SURROUNDING GROUND*Shinya Inazumi1, Tsutomu Namikawa1, Shuichi Kuwahara2 and Shin-ichi Hamaguchi31Shibaura Institute of Technology, Japan;
Marushin Co. Ltd., Japan; 3Yokohama Wright Industries Co. Ltd., Japan2*Corresponding Author, Received: 5 May 2016, Revised: 7 July 2016, Accepted: 22 Nov. 2016
ABSTRACT: 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 decreasein population. The number pile foundations being pulled out is now far greater than that being newly installed.
However, after a pile foundation is pulled out, the mechanical characteristics of the surrounding ground may
be affected by the existence of the resulting hole formed by pulling out. There are no regulations yet on injecting
fillers into pull-out holes, and the influence of filler strength on the surrounding ground is yet to be elucidated.
This study considers the influence of 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, Pull-out hole, Surrounding ground, Two-dimensional dynamic finite-element analysis
surrounding ground is yet to be elucidated.
This study considers the influence of the pull-out
holes of pile foundations on the static and dynamic
characteristics of the surrounding grounds using
two-dimensional dynamic finite-element analysis.
The special qualities required by fillers for being
injected into pull-out holes are also clarified in thisstudy.

1. INTRODUCTION
In Japan, many cities are located on soft ground,and many structures use pile foundations. Therefore,
for land to be reutilized 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 wastes in
the ground is a very difficult problem. In addition,
the presence of such piles remaining in the groundis 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 fromvibration, noise and environmental problems, andhence, the pull-out method is more widely used.
However, the pull-out method also has certain
problems; in particular, a hole is formed when anexisting pile is pulled out of the ground, and if thishole is left unattended, it is possible that the groundsurface 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 andinexpensive. However, as such materials cannot
ensure reliable filling or stable strength, the use ofprocessing 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 the2. DYNAMIC FINITE-ELEMENTANALYSIS
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 input
ground-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 theapplication configuration model and material
parameters in the initial stress analysis and thedynamic total stress elastic plastic analysis.
(4) Perform the initial stress analysis. The analysis
technique used is total stress analysis. In thisstudy, an HD model for the ground material andan elastic model for the hollow portion areapplied.
(5) Took over the calculated ground in stress at (4),perform dynamic total stress analysis. Again, aswith the initial stress analysis, the HD modelfor the ground material and the elastic modelfor the hollow portion are applied. Enter theseismic acceleration at the bottom of theanalytical model.
16International Journal of GEOMATE, July, 2017, Vol. 13, Issue 35, pp. 16-21

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 procedure(b) Filled pull-out hole

2.1 Analytical modelFig. 2 Sectional view

In the analysis, the analytical cross section hastwo 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 ofgravel serving as a support layer, for which the Nvalue is approximately 50. The width of theanalytical cross section is set at 50 m, the thicknessof the clay layer is 18 m, the thickness of the gravel
layer is 8 m and the total depth of the cross section
is 26 m. Two pull-out holes exist in the model at a
spacing of 4 m; the pore diameter is 1 m, depth is20 m and the depth of embedment in the gravel layeris 2 m. To improve the accuracy of the analysis, afiner mesh spacing is used near the pull-out hole.
This finer mesh continues to be used even when thepull-out holes are filled in order to examine thebehavior of the filling. As a boundary condition, inthe dynamic analysis, the bottom is a fixed fulcrum
and the lateral boundary is the equal-displacementboundary. When the moving node on the side of theleft side, node of the other side to the displacement
is the same movement as the node on the side of theleft. Therefore, it is possible to express whether thestratum 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-outholes and one where the pull-out holes are filled.
The analytical cross-sectional view of the ground isshown in Fig. 2. A similar analytical model isshown in Fig. 3. In the case of filled pull-out holesin Fig. 3, the portion surrounded by a red frame isthe pull-out hole portion. The parameters of the HD(a) Empty pull-out hole(b) Filled pull-out holeFig. 3 Analytical model17

International Journal of GEOMATE, July, 2017, Vol. 13, Issue 35, pp. 16-21

2.3 Input Ground-motion Waveform

Table 1 HD model parameters
Parameters
G0 (kPa)’m (kPa) (-)
c (kPa) (°)

Clay layer
27900
900.45250

In the analysis, the waveform of the El Centro
1940 NS earthquake (which was provided by theBuilding Center of Japan) is exerted on thesubstrate’s surface. The maximum acceleration is341.7 cm/s2.

Gravel layer
298485
234
0.40
050

3. RESULTS AND DISCUSSIONS
Figure 4 shows the diagrams of the maximumdisplacement 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 displacementof the ground center in the cases where no pull-out
holes are present and where the pull-out holes havebeen filled.
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. FromFig. 4, it can be seen that a large ground subsidence
occurs in the vertical direction when the pull-out
hole is empty. The maximum subsidence in groundsurface is approximately 60 cm, which is very
dangerous. However, this subsidence does notoccur in the case where the pull-out holes are filled.
Thus, it can be said that filling the pull-out hole isan effective way to prevent 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 behavior of the horizontal displacement underfiller 1 is different from that of the other cases.
In the other cases, displacement to the rightoccurs rapidly at approximately 5 seconds anddisplacement have continued while thedisplacement remained. However, if thedisplacement at 5 seconds is small, then the system
will soon return to its original configuration. From
this fact, it is believed that the behavior of thehorizontal displacement of the ground varies greatly
when the filling material strength is too small. FromFig. 5, it can be seen that the horizontaldisplacement is greatest in the case where filler 3 isused and the displacement is approximate in thecase where no pull-out holes and filler 2 are used.
Figure 8 shows a comparison of the horizontal
displacements of the ground center line. From Fig.
8, it can be seen that rapid displacement of the clay
layer bottom occurs in all cases. In addition, thebehavior of the ground with holes filled by filler 2
is considered to be closest to the behavior of theground without pull-out holes. In the verticaldirection, bulging occurs on the left side of thefilling portion and subsidence occurs on the rightside when fillers 2 and 3 are used. Furthermore, it
can be seen that the displacement increases as theTable 2 Elastic model parameters
Parameters
qu (N/mm2)
E (kN/m2)
 (-)

Pull-out holes (filler)
Filler 1
Filler 2
Filler 3
0.1
0.5
1.0
25280
126400252800
0.48
0.46
0.44

Table 3 Element parameters
Parameters

Claylayer

Gravellayer

t (kN/m3)1521

w (kN/m3)
Constitutivelaw

Pull-outholes(filler)
15

9.8
HD
modelHDmodel

Elasticmodel

model in the clay and gravel layers are shown inTable 1. Table 2 shows the parameters of the elastic
model of the pull-out hole.
2.2 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,
a fluidization treated 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 analyzed 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].
t represents the weight per unit volume of soil;
w represents the weight per unit volume of water;
G0 represents the initial shear stiffness; ’mrepresents the initial average active confiningpressure;  represents Poisson’s ratio; c represents
the adhesive force;  represents the internal friction
angle; qu represents the compressive strength; and Erepresents the elastic coefficient.
18

International Journal of GEOMATE, July, 2017, Vol. 13, Issue 35, pp. 16-21(a) No pull-out hole(b) Empty pull-out hole(c) Filler 1(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
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International Journal of GEOMATE, July, 2017, Vol. 13, Issue 35, pp. 16-21(a) No pull-out hole(b) Filler 1(c) Filler 2(d) Filler 3Fig. 6 Y-direction displacement contour diagrams(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 center20

International Journal of GEOMATE, July, 2017, Vol. 13, Issue 35, pp. 16-21

filler strength increases.

5. REFERENCES

4. CONCLUSIONS[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.166-167, 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 fluidizedprocessing soil”, Summaries of TechnicalPapers of Annual Meeting Architectural
Institute of Japan, 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),“PublicBuildingConstruction Standard Specification (BuildingWork) 2013 Edition”, MLIT, 2014.

In this study, two-dimensional dynamic finiteelement analysis was used to elucidate the effect ofpull-out holes of foundation piles on the dynamic
behavior of the ground.
The results obtained from the analysis are shownbelow.
(1) Ground subsidence occurs in the vicinity of apull-out hole when the hole is left empty,
particularly in the area sandwiched between
two pull-out holes. A very large subsidence
occurs in a wide range of ground surfaces if
earthquake ground motion occurs.
(2) When the pull-out holes are filled, groundsubsidence does not occur in the dynamic or
static analyses. For this reason, it is clear thatfilling pull-out holes is effective.
(3) When the filling strength is too small relative tothe strength of the original ground, the ground
may behave in a significantly different way
from the case with no pull-out holes. For thisreason, it is necessary to change the filler
strength to suit the ground conditions.
This study has not taken account of the influenceof different compounding filler materials or
different hole shapes. Therefore, there is a need toinvestigate these conditions as the subject of future
analysis.

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