P13

EXPERIMENTAL INVESTIGATION ON SEISMIC RESPONSE OF ADJACENT STRUCTURESON LIQUEFIABLE GROUND〇Zhuocheng ZHANG, Kyohei UEDA, Yuko SERIKAWA
1. INTRODUCTION
During earthquakes, saturated sandy terrains canTable 1

Configuration of building model spacing and s/B

induce liquefaction, causing buildings in closevalues. *Parentheses denote the prototype values.

proximity to settle unevenly, crack, and tilt. Notable

Case

Gap

instances include the 1999 Adapazari earthquake inNo.

(s value)

Turkey and the 2018 Hokkaido Eastern Iburi

15 mm (0.25 m)

0.05

70.0

earthquake in Sapporo, Japan. Shallow foundation

240 mm (2 m)

0.4

72.2

structures, particularly vulnerable, exhibit excessive

370 mm (3.5 m)

0.7

70.0

settlement and tilting.

4100 mm (5 m)

173.3

Single--70.0

Numerical investigations by Konstantinos et al.1)

s/B

Dr

(%)

found that as the distance between two structures
decreases, they tend to rotate inwards. Increasing
distance leads to outward rotation, with the angle
decreasing as the distance grows. To validate thesefindings and explore seismic-induced soil liquefaction
behaviors, we conducted model shaking tests in acentrifugal field. Our experimental design aligns withsimplified models for shallow foundation design on(a) Twins structures caseliquefiable soils, extensively researched by Ishihara etal. and Tokimatsu et al.2)3)
2. METHODOLOGYThis chapter introduces the experimental model
dimensions on a 1/50 scale, subsequently expressed on
the prototype scale. The s/B value, representing thespacing-to-building breadth ratio, is crucial for data(b)

processing. Four spacing cases as shown in table.1 andFig. 1 Model configuration.

Single structure case

Fig.1 (5 mm, 40 mm, 70 mm, and 100 mm) correspondto s/B values of 0.05, 0.4, 0.7, and 1.0. The experimentaccelerometers and pore water pressure transducers,

involves two standardized steel models (100 mm × 100

monitor different aspects.

mm × 70 mm), with a constant model breadth of 100

A total of 37.2 kg of sand, deposited in four batches

mm. Silica Sand No. 6 and METOLOSE solution

using the air pluviation method, and the METOLOSE

simulate ground conditions. Various sensors, including

solution, 50 times more viscous than water, facilitatedFig. 2 Five-fold amplified Kobe wave.

Fig. 3 Relationship between s/B and relative tilting degree

saturation. Challenges with solution infiltration wereaddressed through repeated evacuations. The consistentsaturation method ensured successful liquefaction forspecific cases.
Seismic excitation gradually increased centrifugal
acceleration to 50g. The five-fold amplified Kobe wave
shown as Fig.2 was chosen based on its observed
effectivenessinpreliminary

testingtoensureliquefaction. Experiments with non-amplified andthree-fold amplified waves preceded confirming thefive-fold amplified Kobe wave. A systematic approachwith three-fold waves initially, followed by five-foldwaves,ensuredreliability

andconsistency

inexperimental outcomes.

(s/B = 0.1), structures tilt inward, transforming into
outward tilting as distance increases. The experimentaligns reasonably well with simulations, but real-world
conditions introduce asymmetry. For s/B = 0.4 and s/B= 0.7, asymmetry is observed with counterclockwise
and clockwise tilting. As distance increases to s/B = 1.0,
outward tilting decreases, consistent with simulations.
Soil-Structure-Soil Interaction (SSSI) enhances
stability but amplifies relative tilting. As distancedecreases, relative tilting increases until a critical point,
after which it decreases. When s/B < 0.05, structures
shift from outward to inward tilting. Analysis of single
structure cases aligns closely with s/B = 1.0.
Comparisons with Yasuda & Fukaya's4) data confirmalignment in most scenarios as shown in Fig.3, withinward tilting observed only when s/B < 0.1.

3. RESULTS ANALYSIS OF TILTING
In this experiment, tilting is defined by settlement
measurements (DL and DR) on the left and right sidesof the model, with the distance between laser
displacement sensors represented as L. Tilting (T) is
calculated considering counterclockwise as positiveand clockwise as negative (Equation 1). Relative tilting
between two structures is computed by subtracting left
structure tilting (TL) from right structure tilting (TR)
(Equation 2). The experiment explores tilting behaviors

The experiment suggests that as buildings approach,inner sides experience smaller settlement due tooffsetting shear stresses. Robust soil columns form
between structures, hindering shear deformations.
Smaller settlement on inner sides supports thisobservation.
REFERENCES
1)

for different distances (s/B values).
Konstantinos et al. observed that at close distances D − DR T = arctan  L
L


(1)

Relative tilting= TL − TR

(2)

2)
3)
4)

Kassas, K., Adamidis, O. and Anastasopoulos, I.:
Structure–soil–structure interaction (SSSI) of adjacentbuildings with shallow foundations on liquefiable soil,
Earthquake Engineering & Structural Dynamics, 51(10),2315-2334, 2022.
Ishihara, K. and Yoshimine, M.: Evaluation of settlements
in sand deposits following liquefaction during earthquakes,Soils and foundations, 32(1), 173-188, 1992.
Tokimatsu, K. and Seed, H. B.: Evaluation of settlements
in sands due to earthquake shaking, Journal of
geotechnical engineering, 113(8), 861-878, 1987.
Yasuda, S. and Fukaya, S.: Differential settlement ofadjacent two spread foundations due to soil liquefaction,
Environmental systems research, 28, 103, 2005.