Publication Date:
2021-06-07
Description:
The diagnosis of the conservation state of monumental structures from constraints to the spatial
distribution of their physical properties on shallow and inner materials represents one of the key
objectives in the application of non-invasive techniques. In situ, CRP and 3D ultrasonic
tomography can provide an effective coverage of stone materials in space and time. The intrinsic
characteristics of the materials that make up a monumental structure and affect the two
properties (i.e., reflectivity, longitudinal velocity) through the above methods substantially differ.
Consequently, the content of their information is mainly complementary rather than redundant.
In this study we present the integrated application of different non-destructive techniques i.e.,
Close Range Photogrammetry (CRP), and low frequency (24 KHz) ultrasonic tomography
complemented by petrographycal analysis based essentially on Optical Microscopy (OM). This
integrated methodology has been applied to a Carrara marble column of the Basilica of San
Saturnino, in Byzantine-Proto-Romanesque style, which is part of the Paleo Christian complex of
the V-VI century. This complex also includes the adjacent Christian necropolis in the square of San
Cosimo in the city of Cagliari, Sardinia, Italy. The column under study is made of bare material
dating back probably to the first century A.D., it was subjected to various traumas due to
disassembly and transport to the site, including damage caused by the close blast of a WWII
fragmentation bomb.
High resolution 3D modelling of the studied artifact was computed starting from the integration of
proximal sensing techniques such as CRP based on Structure from Motion (SfM), with which
information about the geometrical anomalies and reflectivity of the investigated marble column
surface was obtained. On the other hand, the inner parts of the studied body were successfully
inspected in a non-invasive way by computing the velocity pattern of the ultrasonic signal through
the investigated materials using 3D ultrasonic tomography. This technique gives information on
the elastic properties of the material related with mechanical properties and a number of factors,
such as presence of fractures, voids, and flaws. Extracting information on such factors from the
elastic wave velocity using 3D tomography provides a non-invasive approach to analyse the
property changes of the inner material of the ancient column. The integrated application of in situ
CRP and ultrasonic techniques provides a full 3D high resolution model of the investigated artifact.
This model enhanced by the knowledge of the petrographic characteristics of the materials,
improves the diagnostic process and affords reliable information on the state of conservation of
the materials used in the construction processes of the studied monumental structure. The
integrated use of the non-destructive techniques described above also provides suitable data for a
possible restoration and future preservation.
Description:
Copernicus
Description:
Published
Description:
On line
Description:
5T. Sismologia, geofisica e geologia per l'ingegneria sismica
Keywords:
Cultural Heritage
;
Monumental Structures
;
Non-Destructive Testing
;
Close Range Photogrammetry
;
3D Ultrasonic Tomography
;
High resolution 3D modelling
;
Restoration
;
Conservation
;
05.04. Instrumentation and techniques of general interest
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Abstract
