Towers on the Earthen Foundation: New Insights by the Excavation and Boring Survey at the Bayon Temple

Bayon temple, built in the latter half of the 12th century, is one representative temple of the Angkor monuments. To shed light on the foundation structure of the central towers that stand on the elevated terrace, archaeological excavation and boring tests were conducted. Based on these surveys, a unique foundation structure was revealed under the central towers. It was confirmed that there is no laterite or sandstone support structure directly beneath the upper structure, and that there is only compacted soil at a thickness of approximately 16 m above the natural sedimentary soil. On the other hand, a laterite masonry 6 m thick and 7–9 m wide was confirmed from around the compacted soil. In other words, the heavy load of the central towers is supported by compacted soil that is constrained from the sides by a laterite structure. In addition, the boring surveys provided new insights into the low structural property of the backfilled soil after the past excavation survey below the central tower and the extension process of the elevated terrace supporting the central towers. Delivered information about the foundation structure and material of central towers, including soil property, water table, water contents, and bearing capacity will be valuable for the future structural assessment of this temple.