Nonlinear 2D and 3D Finite Element Static and Dynamic Analyses of the Main Pyramid of Huaca de la Luna, Peru

Huaca de la Luna is a monumental earthen complex near Trujillo in north coastal Peru built from 200 AD to 850 AD by the Moche civilization. Its principal structure – a stepped pyramid built with millions of adobe bricks on sloping bedrock and soft soil – presents severe structural damage at the NW corner. The static and dynamic response of the pyramid is systematically analyzed using 2D and 3D nonlinear FE models derived from a detailed evaluation of archaeological, material, and geotechnical data. The analyses are performed in Abaqus/CAE Explicit using concrete-damaged plasticity and Mohr-Coulomb formulation for adobe construction and soft soils, respectively. The time-evolution of elastic strain and dissipative plastic energy is used to follow the development of local damage conditions up to structural collapse. A critical cross-sectional configuration is identified through 2D FE plane strain sensitivity analysis of the static and lateral capacity to (a) pyramid stepped west side profile, (b) underlying bedrock configuration, and (c) adobe tensile strength. 3D models derived from the 2D critical configuration are then evaluated in terms of static stability, lateral capacity, and failure mechanisms. Results indicate that horizontal accelerations produce large structural failure at the pyramid northwest corner similar in extent and location to the present damage.