Geotechnical approaches on the seismic risk assessment for architectural heritages at historical sites using field and centrifuge tests

This paper describes a research methodology for the seismic risk assessment of architectural heritages at historical sites from a geotechnical engineering viewpoint. Field seismic tests, site-specific ground response analysis, and geotechnical centrifuge model tests with an earthquake simulator were used to determine the geotechnical characteristics of Cheomseongdae, which is a representative of Korean architectural heritage. This artifact is known to be the oldest astronomical observatory in Asia. According to historical records, the Gyeongju area where Cheomseongdae is located has suffered from numerous medium-scale earthquakes. Based on site investigation and ground response analysis of scenario earthquakes, the ground around Cheomseongdae is highly susceptible to site amplification. In addition, Cheomseongdae is a masonry structure that is apparently vulnerable to horizontal dynamic loads such as earthquakes. However, features such as the filler of the lower half, irregularly shaped inner stones that can induce high frictional resistance, eight long horizontal tie stones inside the artifact, and a grid of interlocking headstones are recognized to increase the structure’s resistance to horizontal dynamic loads despite its appearance. Through field and centrifuge tests, a geotechnical approach to the seismic risk assessment of architectural heritages at historic sites is established. The test results verify our ancestors’ “seismic design” technology.