Influence of Destructuration on the Compression Behaviour of a Weak Rock

The literature has highlighted the behaviour of several weak rocks and the role of structure in determining them. The need for understanding their behaviour is due to the instabilities or collapse that may involve human settlements built on these materials which are widespread all over the world. In previous studies, the authors highlighted that in Marsala, Sicily, underground calcarenite quarries have been involved in a number of collapses that have seriously damaged numerous overlying buildings. In order to investigate the influence of destructuration on the behaviour of the calcarenite of Marsala, this paper presents a preliminary investigation of the compression behaviour of the intact rock and of the same weak rock in a destructured state. A petrographic and physical characterisation of the material was carried out together with oedometer and isotropic compression tests. The investigation has highlighted behaviour not previously identified for other weak rocks in which the pores seem to play a key role; the destructured material can no longer be considered, as generally assumed for other weak rocks, as a reference

Influence of destructuration on the compression behaviour of a weak rock

The literature has highlighted the behaviour of several weak rocks and the role of structure in determining them. The need for understanding their behaviour is due to the instabilities or collapse that may involve human settlements built on these materials which are widespread all over the world. In previous studies, the authors highlighted that in Marsala, Sicily, underground calcarenite quarries have been involved in a number of collapses that have seriously damaged numerous overlying buildings. In order to investigate the influence of destructuration on the behaviour of the calcarenite of Marsala, this paper presents a preliminary investigation of the compression behaviour of the intact rock and of the same weak rock in a destructured state. A petrographic and physical characterisation of the material was carried out together with oedometer and isotropic compression tests. The investigation has highlighted behaviour not previously identified for other weak rocks in which the pores seem to play a key role; the destructured material can no longer be considered, as generally assumed for other weak rocks, as a reference

Flowable Mixtures of Treated Soils for Repairing Damage Caused by Burrowing Animals

The adoption of flowable mixtures of treated soils is suggested as a sustainable solution for repairing the damage caused by burrowing animals in the Po River embankments. Soil from damaged sites is proposed to be mixed with lime or cement, other additives, and water in order to obtain mixtures with an adequate compromise between viscosity—which is crucial for flowing the mixture into the hole with site machines—and shrinkage that might occur over time according to the hole boundary conditions. Injections of soil-treated mixtures must guarantee hydraulic and mechanical continuity with the existing embankment and reduce shrinkage phenomena that frequently occur with cement–bentonite grout, which is commonly used for this purpose. This study presents an interdisciplinary experimental programme in the search for the best formulation among several recipes of mixtures of soils, collected from four embankments of Po River or its tributaries and treated with lime or cement, different percentages of water, and other additives. The mixtures, after soil classification and viscosity determinations, were then used to create samples for which shrinkage and erosion susceptibility were estimated, respectively, through a non-standard volume measurement procedure and crumb tests. An abacus will be then proposed in order to give, as a first estimation, applicative indications on the best recipe among the investigated mixtures

Numerical modelling of slope–vegetation–atmosphere interaction: an overview

The behaviour of natural and artificial slopes is controlled by their thermo-hydro-mechanical conditions and by soil–vegetation–atmosphere interaction. Porewater pressure changes within a slope related to variable meteorological settings have been shown to be able to induce soil erosion, shrinkage–swelling and cracking, thus leading to an overall decrease of the available soil strength with depth and, ultimately, to a progressive slope collapse. In terms of numerical modelling, the stability analysis of partially saturated slopes is a complex problem and a wide range of approaches from simple limit equilibrium solutions to advanced numerical analyses have been proposed in the literature. The more advanced approaches, although more rigorous, require input data such as the soil water retention curve and the hydraulic conductivity function, which are difficult to obtain in some cases. The quantification of the effects of future climate scenarios represents an additional challenge in forecasting slope–atmosphere interaction processes. This paper presents a review of real and ideal case histories regarding the numerical analysis of natural and artificial slopes subjected to different types of climatic perturbations. The limits and benefits of the different numerical approaches adopted are discussed and some general modelling recommendations are addressed

CHARGE syndrome and congenital heart diseases: systematic review of literature

CHARGE syndrome (CS) is a rare genetic disease that affects many areas of the body. The aim of the present systematic review was to evaluate the prevalence and types of congenital heart diseases (CHDs) in CS and their impact on clinical outcome. A systematic review from 1981 to September 2022 was conducted. Clinical studies that reported the association between CS and CHDs were identified, including a case report of a rare congenital anomaly of the aortic arch (AA) with persistent fifth aortic arch (PFAA). Demographic, clinical and outcome data were extracted and analyzed. Sixty-eight studies (44 case reports and 24 case series; n=943 CS patients) were included. The prevalence of CHDs was 76.6%, patent ductus arteriosus (PDA) 26%, ventricular (VSD) 21%, atrial septal defects (ASD) 18%, tetralogy of Fallot 11%, aortic abnormalities 24%. PFAA has not been previously reported in CS. Cardiac surgery was performed in more than half of CS patients (150/242, 62%). In-hospital mortality rate was about 9.5% (n=86/900) in case series studies and 12% (n=5/43) in case reports, including cardiovascular (CV) and non-CV causes. CHDs and feeding disorders associated with CS may have a substantial impact on prognosis. CHDs were usually associated with CS and represent important causes of morbidity and mortality. PFAA, although rare, may also be present. The prognosis is highly dependent on the presence of cardiac and non-cardiac developmental abnormalities. Further studies are needed to better identify the main causes of the long-term outcome of CS patients

Terreni collassabili e processi di instabilità nella Valle dei Templi

Il complesso sacrale ellenistico della Valle dei Templi di Agrigento, Patrimonio UNESCO dell’Umanità, si snoda lungo la cresta di un banco di calcarenite, poggiante su un livello di sabbie. I costoni, in corrispondenza delle pareti calcarenitiche, risultano frequentemente in condizioni di equilibrio limite anche in prossimità delle principali strutture archeologiche, fra cui il Tempio di Giunone, il Tempio della Concordia, e il Tempio di Vulcano, le aree dei Donari e del Santuario Rupestre dedicato a Demetra, e la Necropoli Paleo–Cristiana. Tali strutture sono minacciate da fenomeni di instabilità e, in taluni casi, dall’arretramento del versante sino ad ora attribuito alla mesostruttura ed a fenomeni di erosione selettiva e scalzamento al piede. Recenti studi hanno individuato per le sabbie parzialmente sature, sovrastate dalle calcareniti, il tipico comportamento dei terreni collassabili caratterizzati da struttura aperta e metastabile, nei quali un incremento del contenuto d’acqua può innescare notevoli variazioni volumetriche. Sulla base di rilievi in sito, di prove di laboratorio e di analisi numeriche agli elementi finiti è stato possibile ipotizzare il ruolo attivo delle sabbie nei fenomeni di dissesto consentendo una nuova lettura e interpretazione dei fenomeni di instabilità

Influence of the Soil-atmosphere Interaction on the Collapse of Sand in the Valle dei Templi in Agrigento

AbstractThe sacral complex of the Valle dei Templi in Agrigento, belonging to the UNESCO Heritage Site List, stands over the crest of a stiff calcarenite bench, which overlies a layer of partially saturated carbonate sand. The retrogression of slopes and toppling phenomena that have occurred in the past, caused by the undermining combined with the discontinuity pattern, threaten some of the more relevant archaeological structures. Recent studies identified an open and metastable structure, typical of collapsible soils, for the sand layer under the calcarenite bench. In the sandy collapsible layer, significant vertical strains occur rapidly when the water content changes locally, decreasing suction and causing differential settlement and an increment of tensile stresses in the above calcarenites, where discontinuities might arise or increase their opening, resulting in possible progressive failure. By using meteorological and rainfall events data, the research presented here is focused on the study of the evapo-transpiration of a one-dimensional model of sand which was carried out in order to predict the water content change in the sandy layer. Successively, by calibrating the results through oedometer tests, the increments of water content were correlated to the amount of collapse. A first assessment of the influence of the soil-atmosphere interaction on the mechanism of collapse is then proposed

Evaluation of cliff recession in the Valle dei Templi in Agrigento (Sicily)

The sacral complex of the Valle dei Templi in Agrigento, added in the UNESCO Heritage Site List, stands over the crest of a rigid calcarenite cuesta, which overlies a layer of partially saturated (S = 6–12%) carbonate sand. In turn, the sand stratum lies on a thick stratumof clays. The environment is highly prone to landslides as highlighted by several previous studies that identify the undermining of slopes and the discontinuity pattern, occurred in the late Neotectonic phase, as causes of cliff failure. For wider and less exposed areas, where the undermining local instabilities can be present because of the specific morphology of the site, a recent research has proposed a new interpretation of the failure general mechanism. The new hypothesis here proposed would ascribe to the collapsible behaviour of the sand; both the failure mechanisms of the cliffs and the development of the discontinuities in the rock mass. A unitary framework is then proposed. A series of direct shear and oedometer tests was performed on the collapsible sand samples and values of collapse potentialwere estimated. As typical for collapsible soils when flooded, vertical strains occurred rapidly causing an increase of shear stresses in the upper calcarenite, characterised by low values of yielding and low values of tensile strength. As a consequence, additional discontinuities occur, volumes of rock fall and cliffs move back. Both by means of in situ surveys and the analyses of involved rock deformability and strength characteristics, a soilmodelwas considered and a modelling process developed. The model results were compared with measurements of displacements as well as dimensions of fallen blocks and consequently the comprehension of the effect of sand collapse was then possible. The identification of the new mechanism key factors allows the definition of the soil parameters that need to be monitored. In order to prevent the cliff recession for the archaeological site, the work proposes a plan of monitoring methods. These methods will be able to estimate the cliff recession, to localize “sensitive areas” and to quantify the parameters that could activate the instabilities

Meccanismi di collasso nelle Latomie di Siracusa

The aim of this work is to support, through geomechanical methods, the historical hypothesis proposed by the archaeologists according to which the latomiae of Syracuse, ancient Greek quarries, were originally mainly developed underground. In order to reach this objective, the finite elements numerical modelling was applied. The input data were inferred from the geologic history, from different archaeological reports and from the geomechanical characterization both of the intact rock and of the rock mass. The study highlighted the geotechnical events which modified the shape and the safety conditions of these amazing ancient quarries over the centuries.Il presente lavoro si propone di corroborare le ipotesi accreditate presso gli archeologi, secondo i quali l’attuale conformazione delle Latomie di Siracusa, cave greche risalenti al VII- V sec. a.C., ed in particolare della Latomia del Paradiso, sia imputabile a crolli che hanno interessato un imprecisato numero di ambienti ipogei oggi scomparsi. Attraverso una modellazione numerica, in cui i dati di input sono stati desunti dalla ricostruzione delle vicende geologiche dell’area di Siracusa, da ricerche bibliografiche e d’archivio relative alla storia delle latomie e dei manufatti presenti nel sito, dalla caratterizzazione geomeccanica della roccia e dell’ammasso, sono stati messi in luce gli eventi che possono avere determinato l’attuale configurazione delle cave storiche e l’insorgenza di fenomeni di instabilità