1,721,105 research outputs found
Sulla subsidenza dell'abitato di Sarno
No full textNel Comune di sarno si sta verificando un fenomeno di subsidenza che ha causato gravi danni a alcuni edifici. Per individuare le cause sono state eseguite numerose indagini di sito e di laboratori
Emungimento delle acque e cedimenti nell'abitato di Sarno: analisi preliminare
No full textNel Comune di Sarno (SA) si sta verificando un fenomeno di subsidenza che ha già causato gravi danni ad alcuni edifici. Per individuarne le cause e seguirne l’evoluzione sono state intraprese indagini in situ e in laboratorio. Nel presente lavoro si riporta un inquadramento delle problematiche sulla base dei dati disponibili. I risultati, ancorché preliminari, permettono d’individuare una stretta correlazione fra lo sfruttamento delle acque sotterranee praticato intensamente in tutto il comprensorio e gli abbassamenti dei livelli di falda. Questi ultimi, pur
essendo contenuti, hanno prodotto cedimenti notevoli del sottosuolo a causa della presenza di torbe molto deformabili che, sottoposte a prove di laboratorio, hanno mostrato caratteristiche di marcata viscosità e grande sensibilità alla composizione del fluido interstiziale
Influence of grass roots on shear strength of pyroclastic soils
No full textThis paper investigates the effects of indigenous vegetation on the shear strength of loose pyroclastic soils of the Campania region (southern Italy); these soils are frequently affected by shallow landslides 1–2 m deep that experience static liquefaction during the post-failure stage. Perennial graminae grasses were seeded in a one-dimensional column 2 m high and filled by pyroclastic soils, allowing the root to grow under atmospheric conditions. A noninvasive sampling procedure was adopted to take the vegetated soil samples, in which the roots were in their natural geometrical distribution. For each rooted sample, the root biomass, RM, was measured and the root volume density, RVD, was calculated. Isotropic consolidated triaxial tests in both drained and undrained conditions were performed on the rooted specimens, as well as on bare specimens as a control. The obtained results showed that the roots generally provided an increment to the soil strength. In drained conditions a reduction in the volumetric deformation was observed, which, under undrained conditions, was reflected in a general reduction of the excess pore-water pressures with a possible inhibition of the static liquefaction occurrence. This study highlights the potential role of grass roots as bio-engineering practice for stabilizing shallow covers of pyroclastic soils
Typical displacement behaviours of slope movements
No full textUnderstanding and quantifying the evolution of landslides are research topics that have always engaged researchers. Indeed, scientific literature provides a large number of contributions introducing and/or applying procedures, which are based on mechanical or phenomenological methods. The first ones are usually implemented to analyse the mechanical behaviour of a single complex phenomenon for which a consistent dataset is available. Phenomenological models are aimed at identifying common characteristics of landslides to be used for different purposes, such as forecasting the time of failure. This paper presents the implementation of a phenomenological model that allows the identification and quantification of well-defined dimensionless displacement trends for a large number of phenomena that are well documented in the literature. The analysed landslides involve different materials and are characterized by different stages of activity induced by seasonal and/or occasional triggering factors. The case studies include the well-known Vajont landslide, for which the obtained results show that the displacement trend was different from those usually characterizing occasionally reactivated landslides, since the beginning of the paroxysmal phase
LiABlock_3D: A Software Tool for Collapse Mechanism Analysis of Historic Masonry Structures
No full textA rigid block model is proposed for collapse mechanism analysis of three-dimensional historic masonry structures subjected to point live loads, seismic-induced lateral loads and settlements. The model is made of polyhedral rigid blocks interacting at no-tension, frictional contact interfaces and can be used to represent complex assemblages and bond patterns. The formulation and the solution procedure of the underlying limit equilibrium analysis problem were implemented in LiABlock_3D, a MATLAB based tool with Graphical User Interface (GUI). The software was designed to import the geometric model from commercial Computer Aided Design (CAD) tools, thus allowing high flexibility of structural configurations and masonry patterns. The graphical interface is also used to define material properties as well as boundary and loading conditions. Numerical and experimental case studies from the literature were analyzed to show the ability of the model developed in predicting the collapse behavior of a variety of structural typologies. Those include arches, vaults, and domes under vertical and horizontal live loads and spreading supports. A two-story masonry building with a barrel vault at first level is also analyzed under variable lateral loads and support movement. Potentialities and limitations of the proposed formulation and tool are discussed on the basis of the results obtained and also in terms of computational efficiency
Application of Liablock_3D to the analysis of failure modes in masonry structures subjected to seismic action
No full textThe paper deals with the application of LiABlock_3D, a novel software tool developed at the University of Naples Federico II, to the case study of an historic masonry viaduct listed by UNESCO as World Heritage Site. LiABlock_3D analyses masonry structures under seismic lateral loads and automatically predict the potential failure modes of complex assemblages in terms of local and global collapse mechanisms. The numerical formulation is based on limit equilibrium analysis and mathematical programming is used to solve the contact problem. Masonry structures are represented as a collection of three-dimensional rigid blocks. Once the geometry of the construction has been generated (i.e. using different CAD tools or MATLAB® scripts for parametric analysis), the numerical model requires few parameters as input data, such as the unit weight of materials and the friction coefficient. Several loading conditions can be considered, assuming different loading axis and load distribution (uniform and/or concentrated loads can be applied). With respect to failure condition, LiABlock_3D considers no-tension, frictional contact interfaces with infinite compressive strength. Opening and sliding failure conditions are considered. In order to show the potentialities and limitations of the developed software, a comparison of the outputs provided by LiABlock_3D with those obtained by Finite Element Analysis is presented and discussed as well
Sperimentazione sulla risposta idraulica di terreni piroclastici radicati con graminacee.
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