Behavior Prediction and Monitoring of a Deep Excavation in the Historic Center of Brescia

The construction of a new underground car park in the historic center of Brescia (Northern Italy) required the execution of a 130m long, 23m wide and 15-20m deep excavation which was supported by concrete multi-anchored diaphragm walls. The site is located between two facing ancient walls (15-16th century) that support 3-4 storey buildings in precarious conditions. The soil stratigraphy comprises a superficial layer of made ground over a clayey to sandy soil deposit supporting a perched water table. A comprehensive monitoring system was set up before construction that included inclinometers, precise leveling and automatic structural monitoring by means of a high-precision total station. A number of finite element numerical analyses were conducted using different constitutive laws for the soil to evaluate the behavior of the retaining structure and safety of adjacent buildings. The simple linear elastic-perfectly plastic constitutive law predicted unrealistic soil behavior and unreliable effects on adjacent structures. The result of numerical analyses performed with soil models that include isotropic hardening with stress and strain stiffness dependency compared well with measurements

Compression and Creep of Venice Lagoon Sands

A laboratory test program was conducted to evaluate the one-dimensional (1D) compression and creep properties of intact sand (and silty-sand) samples from a deep borehole at the Malamocco Inlet to the Venice Lagoon. The tests were performed with a constant rate of strain consolidometer and included special procedures for trimming the frozen samples and measuring strains during thawing and backpressure saturation. The specimens had variable fine fractions ranging from 6 to 21% and mica contents ranging from 1 to 10%. The results confirmed that there is a strong correlation between the creep rate coefficient and the compressibility index and between the swelling index and mica content. The compression behavior in all tests is well described by a nonlinear compression model with a unique limiting compression curve and a variable transition parameter that reflects the fines and mica content. Creep tests performed at different confining pressures are also well represented by a simple two-parameter model

On the Swelling Behaviour of Weak Rocks Due to Gypsum Crystallization

AbstractThe paper describes the case of an industrial pavement in Northern Italy, subjected to significant uplift (up to 0.2-0.4 m) due to the response of the rock mass below the concrete floor. The study included monitoring the pavement for a long period of time, the execution of a geotechnical investigation campaign and a number of X-ray diffraction analyses. The results of the investigation suggested that a strong correlation exists between the uplift of the pavement, the swelling behaviour of the material exposed by the excavation and the chemical process of gypsum crystallization

Indagine metodologica per l'ottimizzazione dei programmi di intervento nell'Alpago (Belluno)

La conca dell'Alpago è situata in provincia di Belluno a oriente della Val Belluna e a settentrione del Passo di Fadalto. Pur sviluppandosi su un territorio di limitata estensione, la zona presenta una serie di problematiche di carattere scientifico, sociale ed economico di estremo interesse, tra le quali spicca la generale situazione di instabilità dei versanti. I movimenti franosi coinvolgono formazioni di natura flyshoide che dal punto di vista geotecnico possono essere classificate come strutturalmente complesse. Dopo aver brevemente illustrato la situazione geologica, idraulica e geotecnica della zona, gli Autori presentano le problematiche relative al piano di sistemazione del sottobacino idrografico del torrente Borsoia, confrontando le situazione antecedenti e successive ai lavori di sistemazione di un tratto significativo dell'asta torrentizia