Assessment of Excavated Tunnels Stability in the Maya Archeological Area of Copán, Honduras

Archaeological buried structures have received less attention than aboveground historical structures, which seems evident given the visual impact of the latter. Archaeological structures present specific issues related to stability during excavation and after being exposed. This paper addresses a UNESCO world heritage site in Honduras (Copan), which has about 4 km of tunnels in a complex organization that were dug, in the last 100 years, for the purpose of investigation of buried structures under a temple complex. The objective of this work is to assess the safety of the tunnels, helping on the decision of back-filling the tunnels, adding new masonry linings and allowing access in current conditions (possibly with measures to avoid water infiltration). First, the long network of tunnels was categorized into different sections either in an earthen fill only or in presence of a masonry lining. Then, the stability of these sections was discussed as a function of the increase of soil saturation. It was found that unlined tunnels safety is likely to be compromised for a saturation higher than 70%, whereas lined tunnels do not fail when the soil becomes fully saturated, as far as drainage is ensured. Finally, this work allowed to issue recommendations on actions related to the site.