Influence of Suction on the Behaviour of Retaining Walls in the City of Naples, Italy

Abstract

The general principles of EUROCODE 2008 prescribe that new constructions are designed, tested and subjected to maintenance during their lifetime. Safety and performance under service conditions are evaluated through the limit states that may occur during the nominal life of the construction. As it is well known, limit states are the conditions beyond which the construction no longer meets the requirements for which the design has been made. In general, during its lifetime, a construction can experience a variation of the external loading. A clear example is the occurrence of a seismic event. Yet, when the soil is in a partially saturated condition, its hydro-mechanical properties can vary with time as a consequence, for example, of rainfall events and subsequent infiltration. A more complex approach is in this case required as a variation of both soil hydro-mechanical properties and external loading can occur. The present work deals with the above issue. In particular, it refers to the city of Naples where unsaturated pyroclastic soils are widespread. Gravity walls, made of tuff masonry, and retaining unsaturated pyroclastic backfills have been analyzed in terms of general behavior and potential damage induced by rainfall events. A Two-Phase Flow module - FLAC2D (Itasca, 2000) has been employed for the numerical analysis.