Embankment on Vertical Drains - Pore Pressures During Construction

Excess pore pressures and consolidation settlements observed during the construction of a trial embankment placed on four different types of vertical drains are examined with the aim of evaluating: undrained pore pressure response, field coefficient of consolidation and drain performance

Leaning Tower of Pisa — Updated Information

The paper is aimed at giving information on the present situation of the Leaning Tower of Pisa and on the activities undertaken for its safeguard by the International Committee appointed in May 1990 by the Italian Government. After a brief review of the subsoil conditions of the structural features and of the observed movements of the Tower, the activities undertaken by the Committee are also summarized

Effects of 2012 Earthquake on the behavior of Ghirlandina tower in Modena

Collapse events, that occurred in the past (such as the Venice Bell Tower in 1902 and the Civic Tower in Pavia in 1989) claimed for the need to assess the long-term behavior of such monuments. A significant effort has been therefore devoted to clarify the reasons for these collapses after many centuries from the construction date. In addition, recent earthquakes in Italy have once again put into evidence the seismic vulnerability of the cultural heritage. To assess this aspect, in many cases the soil-structure interaction cannot be neglected. In this context, a simple but consistent framework for soil-structure interaction analysis is here presented with reference to a case history. It is discussed how the difference in the fundamental frequency observed during seismic events can be associated to non-linearity in soil response, leading to a rotational stiffness of the soil-foundation system consistent with the shear strain level derived from the seismic ground response analysis. Thereafter, the validated soil-structure interaction model has been used to define an equivalent SDOF model of the structure that explains the differential settlements suffered by the Ghirlandina tower in Modena during the 2012 seismic events as well as its behavior since those events

Dynamic Response of Cantilever Retaining Walls Considering Soil Non-Linearity

For many decades the analysis of earth retaining structures under dynamic or seismic conditions has been carried out by means of standard limit equilibrium (Coulomb, M-O) or elastic methods (Wood, Veletsos and Younan). These approaches are simplified, as they make use of considerable approximations which are often applicable only under particular conditions. A different and perhaps more realistic approach is possible using established computer codes, which integrate numerically the governing equations of the soil and wall media. Since these problems may involve significant levels of strain in the backfill, material non-linearity should be taken into account to realistically simulate the response of the system. In the herein-reported study, a parametric analysis is carried out through the finite-difference code FLAC 5.0. Starting from simple cases involving elastic response, and moving gradually towards more realistic conditions, salient features of the dynamic wall-soil interaction problem are addressed. The case of non-linear hysteretic behaviour of soil and flexibility of wall is considered at a second stage. Results indicate that with increasing levels of acceleration, there is a clear transition from elastic behaviour (in which the aforementioned V-Y type methods are applicable), to plastic behaviour in which M-O methods are thought to be more suitable under pseudo-static conditions. The results of the parametric analyses are reported in terms of pertinent normalized parameters, to provide a general framework for the assessment of wall-soil dynamic interaction under strong seismic excitation

The Garisenda Tower in Bologna: Effects of degradation of selenite basement on its static behaviour

The Garisenda tower in Bologna, a 48 m tall structure with a square base of 7.45 meters per side, is characterized by an overall out of plumb of 3.32m in the South-East direction. Its construction dates back to the XI century and, due to its impressive leaning, in 1350–1353 the original height of 60m was reduced to the 48m of the present day (Cavani 1903; Giordano 2000). The tower can be seen as partitioned in a lower portion, with walls composed by two external leaves of selenite stones filled with rubble conglomerate, and an upper portion where the external leaves are made of masonry bricks. Recent investigations have proved that selenite blocks of the basement have been altered as a result of (a) exposition to high temperatures during important fires, that took place at the end of XIV and XVII centuries, and possibly because of the presence of forges (that were demolished at the end of the XIX centuries) and (b) high level of humidity in the inner lower part of the tower. This process has produced a gradual local disintegration of the selenite stones, leading in some case to a reduction of the original 50 to 60 cm thickness by an amount of about 20 cm. The contribution submitted to this conference is aimed at clarifying this important aspect, linked to the ageing and damage of structural stones and the related consequences in terms of stress distribution and concentrations that could induce fracture propagation and sudden collapse of the tower basement