Subsurface water‐content identification in a crypt using GPR and comparison with microclimatic conditions

Abstract

The effects of climate, pollution and human negligence cause severe and sometimes irreversible damage to buildings and monuments of cultural interest. It is well known that the presence of water and/or moisture content in a porous material is the initial cause of deterioration. In a previous paper, the authors reported an integrated study on a building of cultural importance, namely the crypt of the Cattedrale di Otranto in Apulia, Italy, based on non‐destructive integrated biological and physical surveys. The method described was able to identify the ‘internal’ factors responsible for deterioration. It was discovered that the distribution of moisture in the stone depended mainly on adverse environmental conditions, and the presence of wet buried structures in the ground. The first aim of the present study was to identify subsurface water‐content in this same crypt using a ground‐penetrating radar (GPR) technique, and to compare these results with those of the previous microclimatic survey. In particular, the existence of underground discontinuities was verified; we located them and analysed their influence. Moreover, by means of velocity analysis, we obtained a quantitative estimate of the volumetric water‐content under the pavement of the crypt. This finding completes the results of the previous research, as it indicates the causes of the deterioration in the crypt and provides significant information, on the basis of which, effective decisions can be made for safeguarding the historic building.

Assessment of fractures in some columns inside the crypt of the Cattedrale di Otranto using integrated geophysical methods

“…Actually with ground penetrating radar explorations we assessed this presence. In particular the volumetric water content was determined from the dielectric properties of subsurface material, using properly relations [6,18].…”

“…This fact suggests us the existence of an important rising of water from the underground causing visible effects of deterioration in the Crypt [6,18]. Now we investigate the internal state of conservation of some columns focusing our attention on the influence of this evidence on the mechanics of fracturing of the columns itself.…”

“…Some causes of the phenomenon of deterioration of the stone were studied with previous different, non-destructive biological and physical researches [6,18] in the Crypt of the ''Cattedrale di Otranto'' (Apulia, Italy) (Fig. 1).…”

Close-Range Sensing and Data Fusion for Built Heritage Inspection and Monitoring—A Review

“…Since the (crucial for maintenance and damage repairing) inspection of historic buildings must, in many cases, be minimally invasive, making some common and valuable techniques' application not favorable, GPR has acquired great importance as a technique for revealing both historical and structural information [4,[192][193][194][195][196][197][198][199][200][201][202][203][204]. Particularly, some issues of structural interest are the probable presence of fractures [205][206][207], voids [208], infiltrations of humidity [209,210], or metallic bars [211] due to previous restoration works, often not sufficiently documented. GPR evaluation is well advised, especially if new restoration interventions are planned [212,213].…”

Ground Penetrating Radar detection of unmarked historic graves at the Fairlawn Cemetery in Stillwater, Oklahoma

“…The receiving antenna detects the reflected or scattered EM waves off buried objects, and the displayed images can indicate the location and depth of the buried object (Leckebusch, 2005). GPR has become a common geophysical method for detecting un-marked graves at cemeteries (Leucci et al, 2003(Leucci et al, , 2006(Leucci et al, , 2007(Leucci et al, , 2011Thompson et al, 2011). Geophysicists routinely use GPR at sites of burials to locate old graves and generate accurate maps for surveyed sites for safe excavation and restoration of graves (Bristow et al, 2007;Buck, 2003;Conyers, 2006aConyers, , 2006bDoolittle & Bellantoni, 2010;Goodman, 2008;Grasmueck et al, 2004;Hansena et al, 2014;Sutton & Conyers, 2013).…”