Structural and geotechnical engineering assessment of Huaca de la Luna – A massive earthen Moche culture pyramid in Northern Peru

The present paper presents results of a comprehensive engineering analysis for understanding the current structural damage condition of a sector of one of the most representative archaeological complexes in Perú: the main Moche culture pyramid of Huaca de la Luna. It is estimated that this pyramid was built in stages with adobe masonry between 100 and 600 A.D. Severe structural damage was identified near the NW corner during the archeological excavation in the form of damaged walls, fissures, cracks, compressed adobe blocks, and incomplete geometry of perimeter walls. An interdisciplinary team carried out an engineering diagnosis involving: detailed surveying and mapping of the geometry of the complex, multi-scale characterization of the material components, geotechnical assessment of foundation conditions, and advanced numerical modeling to help evaluate the possible reasons for the observed structural damage. The results indicate that the origin for the observed damage is uneven foundation settlements related to a variable foundation layer thickness that is associated to the sloping bedrock at the site of this complex. The complex soil-structure interaction issues associated to the foundation conditions and high foundation pressures in the NW corner of the complex, coupled with the high internal stresses in the lower part of this structure that reach the strength capacity of this fragile material, appear to be the main reasons for the observed damage. This interdisciplinary study provided an effective approach to find a valid and scientific-based explanation for the observed archaeological evidence and open up new engineering and archaeological discussions for finding the most appropriate strategies for future conservation and structural consolidation works at this invaluable Moche culture heritage site.