Field Activities for the Conservation and Sustainable Development of Ta Nei Temple in Angkor, Cambodia (Part XXⅡ) – Archaeological Investigation and Practical Workshop for Conservation and Restoration of Cruciform Terrace in front of the Central Complex
Tokyo National Research Institute for Cultural Properties (TOBUNKEN) and the Authority for the Protection and Management of Angkor and the Region of Siem Reap (APSARA National Authority) in Cambodia are continuing the conduction of a preliminary survey for the restoration of the Cruciform Terrace in front of the Central Complex of Ta Nei Temple as part of a cooperative project.
This Cruciform Terrace of Ta Nei Temple comprises a sandstone exterior wall with laterite substrate and sandstone paving, inside of which is filled with compacted soil layers. Much remains unknown regarding the function and structural characteristics of these inner soil layers, and various approaches for their stabilisation have been explored in the conservation of other monument structures at Angkor.
Therefore, archaeological and geotechnical surveys were conducted to clarify the configuration of the inner structure of the Cruciform Terrace and its construction process, as well as to examine the appropriate restoration methods of the Terrace during the mission from 20 May to 21 June 2026.
An archaeological excavation survey conducted at four trenches confirmed that the inner soil layers were constructed using different types of soils, and the stone masonry technique applied to this Terrace differs from the manner commonly used for other Khmer temple architecture. It was also clarified that intrusion of tree roots caused deformation of the side walls. Furthermore, several new clues were obtained regarding the construction process in relation to the adjacent rectangular terrace.
The geotechnical survey was carried out as the second session of “the practical workshop for the Cruciform Terrace restoration,” under the guidance of Professor KUWANO Reiko from the University of Tokyo. Three staff members from the APSARA National Authority participated, conducting dynamic cone penetration tests on-site targeting the soil layers of the Terrace, as well as laboratory tests on the collected soil samples, including dry density, particle size distribution, and compaction test. In addition, we visited the Institute of Technology of Cambodia in Phnom Penh to discuss the implementation of triaxial compression and permeability tests for those soil samples.
The survey results will be used in a structural assessment of the Terrace, followed by a discussion with the APSARA National Authority on appropriate restoration methods for the Terrace.