Identifying damaged areas inside a masonry monument using a combined interpretation of resistivity and ground-penetrating radar data

Abstract

The Bayon Complex in the Angkor heritage site, Cambodia, has been damaged by weathering. To plan its long-term preservation, it is essential to investigate its internal structure and the degree of damage within the masonry monument. This study shows results of ground-penetrating radar (GPR) and electrical exploration surveys, and an interpreted section of the internal structure and moisture distribution in the masonry monument. The GPR can detect boundaries between stone blocks and between stone blocks and compacted soil. Electrical resistivity can indicate moisture distribution with high reliability in combination with GPR sections. The top surface zone of the terrace structure of this monument is composed of three layers of stone blocks, and the zone below a depth of 55–60 cm is composed of compacted soil. Rainwater penetrates into the terrace through gaps between the stone blocks and drains from vertical walls through cavities in the top part of the compacted soil. Damaged areas are limited to a part of the terrace, and a large area has remained in good condition. This study shows that a combination of electrical resistivity and GPR data is useful for investigating the internal structures and classifying the degree of damage to old stone structures.

This study shows results of ground-penetrating radar and electrical exploration surveys, and an interpreted section of the internal structure and moisture distribution in the Bayon Complex in the Angkor heritage site, Cambodia. Rainwater penetrates into the monument through gaps between stone blocks and drains from vertical walls through cavities in the top part.

Key words::

• archaeological survey, Bayon Complex, electrical exploration, ground-penetrating radar, groundwater channel.

Acknowledgements

This survey received support from Dr K. Okuda of Waseda University and was performed as part of a research project of Conservation and Restoration of the Bayon Temple in the Angkor Thom Complex, which is a project of phase III of the Japanese Government Team for Safeguarding Angkor (JSA). The survey in the Angkor area received permission and cooperation from the Authority for the Protection and Management of Angkor and the Region of Siem Reap (APSARA). Some of the survey equipment was supplied by Dr T. Yokota of the National Institute of Advanced Industrial Science and Technology (AIST). Survey data in this paper were shown in an annual technical report on the survey of Angkor Monument 2006–2007, edited by Dr T. Nakagawa of JSA. Part of this paper was published as a conference proceeding of the Society of Exploration Geophysicists of Japan (SEGJ) in 2011. Comments and suggestions of editors, anonymous reviewers and Dr L. Thomas helped to improve the manuscript.