483
Site characterization by seismic dilatometer (SDMT): the Justice Court of
Chieti
Caractérisation du site par dilatomètre sismique (SDMT): la Cour de justice de
Chieti
Amoroso S., Totani F., Totani G.
University of L’Aquila, Italy
ABSTRACT: A detailed investigation of several seismic dilatometer (SDMT) tests was performed in 2011 on Chieti hill to restore the
Justice Court, an historical building damaged by the April 6, 2009 L’Aquila earthquake. Moreover, boreholes were carried out to
investigate foundation base level and cyclic simple shear tests with double sample were realized to analyze the seismic site res- ponse.
The paper illustrates the potential of the seismic dilatometer to efficaciously approach a geotechnical problem by the inter- pretation
of SDMT parameters, as the shear wave velocity
V
S
, the constrained modulus
M
and the horizontal stress index
Kd
. Fi- nally, the
paper combines SDMT results with laboratory data to analyze the site response of the Justice Court.
RÉSUMÉ : Une étude détaillée de plusieurs sismiques dilatomètre (SDMT) tests a été réalisée en 2011 sur la colline de Chieti pour
restaurer la Cour de justice, un bâtiment historique endommagé par le tremblement de terre qui a eu lieu le Avril 6 2009 à L'Aquila . En
outre, des sondages ont été effectués pour étudier le niveau de base de fondation et cycliques essais de cisaillement simple avec
échantillonnage double ont été réalisées pour analyser la réponse sismique du site. Cet article montre efficacement le potentiel de la
dilatomètre sismique à l'approche d'un problème géotechnique par l'interprétation des paramètres SDMTs, comme la vitesse de
l'onde de cisaillement
V
S
, le module
M
et l'indice de contrainte horizontale
Kd
. Enfin, le document combine les résultats SDMT aux
données de laboratoire pour analyser la réponse du site de la Cour de justice.
KEYWORDS: seismic dilatometer, horizontal stress index, shear wave velocity, site response analysis, local site effetcs.
1
INTRODUCTION
The April 6, 2009 L’Aquila (Italy) earthquake (
M
W
= 6.3)
caused heavy damages not only in the city of L’Aquila basin but
also in few cities, as Chieti, approximately 100 km far from the
epicenter. In this respect, a detailed investigation of several
seismic dilatometer (SDMT) tests (Marchetti et al., 2008) in
virgin soils and inside boreholes backfilled with sand (Totani et
al. 2009), foundation boreholes and cyclic laboratory tests were
performed in 2011 on Chieti hill to restore the Justice Court, an
historical building damaged by the above mentioned earth-
quake. The geotechnical campaign allowed to characterize the
subsoil, to investigate foundation base level and to analyze the
seismic site response of this construction. In particular, the pa-
per illustrates the potential of the seismic dilatometer to effica-
ciously approach a geotechnical problem by the interpretation of
SDMT parameters, as the shear wave velocity
V
S
, the constrai-
ned modulus
M
and the horizontal stress index
Kd
, even combi-
nig SDMT results with laboratory data for the evaluation of the
local site effects (e.g. topography, soil conditions) with modo-
dimensional (1D) and bidimensional (2D) seismic site response
analyses.
2 GEOTECHNICAL INVESTIGATION ON CHIETI HILL
A detailed investigation of eleven SDMT tests, six in virgin
soil, each 10-20 m in depth, and five inside boreholes backfilled
with sand, each 30-50 m in depth, were performed in 2011 on
Chieti hill to restore the Justice Court, an historical building
damaged by the April 6, 2009 L’Aquila earthquake. Moreover,
boreholes were carried out to investigate foundation base level
and cyclic simple shear tests with double sample were realized
to analyze the seismic site response. The historical centre was
built on sandy and arenaria deposits (45 m in depth), while
moving towards the bottom of the slope the colluvial cover start
to emerge over the OC silty clay, as shown in Figure 1 together
with the shear wave velocity V
S
profiles.
Figure 2 emphasizes the main reason of the damage due to the
seismic action on the construction. As shown by the inspection,
the structure appears to be considerably fissured in its Southern
part, while in the Northern area it seems to be intact (Figure 2a).
This aspect can be justified referring to the four SDMTs per-
formed along the perimeter of the building (Figure 2b). SDMT1
and SDMT4, as well as SDMT3 and SDMT2 profiles, can be
coupled. In fact, in the Northern part of the Justice Court the
constrained modulus
M
reaches on average values over 100
MPa and the horizontal stress index
Kd
indicates OC soils. In-
stead, in the Southern area, until about 8.00 m in depth,
M
as-
sumes very low values (under 50 MPa) and
Kd
is about equal to
2 and thus
Kd
individuates NC layers (TC16, 2001). In both the
cases
V
S
appears less sensible to the stress history and the stiff-
ness of the deposits compared to
M
and
Kd
. In addition, the
boreholes on the foundations illustrate that in the Southern part
