Mechanical behaviour of Palermo and Marsala calcarenites (Sicily), Italy

Abstract This paper aims at finding a framework for the Sicilian Calcarenites relating the strength and the deformability of these materials to their geological and structural features: fabric, bonding, initial and actual specific volume. In particular, this study sets out to separate the effects of fabric and of bonding on the mechanical response. The investigated lithotypes, Calcarenites from Palermo and Marsala, outcropping in many areas of southwestern Sicily, are characterized by sudden changes in their deformability, strength and permeability characteristics. The geotechnical identification, by means of computerized axial tomography and thin section petrographic analysis suggested a s…

The open metastable structure of a collapsible sand: fabric and bonding

This paper deals with the compositional and textural characteristics determining open metastable structures in the pleistocenic sand outcropping in the Agrigento district (Sicily). The aim of the study was to individuate the bonding types occurring between grains that could generate matric suction phenomena. The composition and microfabric were characterised by means of granulometry, porosimetry, permeability, optical and ESEM-EDS microscopy, thermogravimetry and XR diffractometry, electric conductivity, and ionic chromatography. The data thus acquired show that the skeleton of the sand is constituted mostly by bioclasts and microfossils, calcite and quartz monocrystalline grains. Moreover,…

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.

Comportamento meccanico di tipiche calcareniti della Sicilia: Risultati preliminari

Terreni collassabili e processi di instabilità nella Valle dei Templi

The sacral complex of the Valle dei Templi in Agrigento, included in the UNESCO Heritage Site List, stands over the crest of a rigid calcarenite cuesta, which overlies a layer of partially saturated carbonate sand. The environment is highly prone to landslides and the calcarenite stratum is often in limit equilibrium conditions. Toppling phenomena threaten some of the more relevant archaeological structures such as the Giunone's Temple, the Vulcano's Temple, the Santuario rupestre and the palaeochristian Necropolis. As highlighted by several previous studies, the instabilities and the recession of slopes have been caused by the undermining of slopes combined with the discontinuity pattern. …

Valutazione dei parametri della resistenza al taglio delle discontinuità con l’ausilio del laser scanner

Valutazione dell’alterazione con laser scanner negli ammassi a struttura orientata e nella diagnostica dei beni monumentali

The applications of laser technology in the field of Rock Mechanics are at a stage of development that allow a reliable use for the reliefs of the mesostructure and for the morphological reconstruction of monuments in place of traditional techniques such as, for example, photogrammetry. The most recent research suggests that the laser may also allow assessment of characteristics such as roughness, which is known to affect the shear strength of discontinuities. Assessing the ratio between the energy of the reflected ray and the one emitted by the instrument, called "reflectivity (I)", it seems possible, also get information on the status of surface discontinuities or areas of historic monume…

Role of particle characteristics in the compression behaviour of gap-graded sands

Abstract The compression in gap-graded mixtures of sands with combined mineralogy has been investigated in recent research, focusing on the key factors that might imply the occurrence of convergent or non-convergent paths in compression (i.e., transitional or non-transitional behaviour). From previous work, the mineralogy of a matrix composed of larger grains seems to determine the possibility of the occurrence of transitional behaviour. Hence, if there is a strong and stiff matrix made of quartz sand particles, which are either larger than or at least of similar size to the other component, then non-convergent compression paths (i.e., transitional behaviour) are likely to occur. As a furth…

Collapsible intact soil stabilisation using non-aqueous polymeric vehicle

Abstract This paper presents the results of an experimental study that had the goal of understanding the effects of treatment with polyethylene glycol (PEG)/nanolime mixtures on collapsible soil behaviour. In a previous study, the use of pure PEG offered a good improvement in the stability of collapsible soil, but the stabilisation effect only lasted for a limited time. To investigate the stabilisation potential of PEG/nanolime systems for collapsible sand, different mixtures were prepared at increasing nanolime weight ratios. The suitability of the stabilised soil was examined on the basis of collapsibility, oedometer, shear, and water vapour permeability tests, and through optical microsc…

The Effects of Structure on the One Dimensional Compression Behaviour of a Porous Calcarenite

Human settlements built on weak rock deposits are often characterized by instabilities or collapse that may involve the underground cavities and consequently the above buildings. Underground calcarenite quarries in Marsala have been involved in a number of collapses that have seriously damaged numerous buildings. Unfortunately proper engineering solutions have not yet been identified according to the different and special cases and to the properties of this structured material. In order to investigate structure effects on the behaviour of the porous calcarenite of Marsala, this paper presents a comparison between the one dimensional compression behaviour of the intact rock and of the same w…

Destructuration of typical Sicilian calcarenites

The paper discusses some interesting features of Sicilian fine grain calcarenites. Uniaxial, triaxial, oedometer and isotropic compression tests were undertaken on intact specimens of two types of calcarenite in order to investigate their mechanical characteristics. It was found that the strength and deformability is significantly influenced by the structure (fabric and bonding) and by the destructuration processes. A better understanding of fracture development behavior is gained through a combination of acoustic emission and photographic monitoring on non-homogeneous samples with natural pre-existing heterogeneities due to cementation or to density. The results show that the destructurati…

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

Abstract 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 stratum of 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 in…

Rock decay phenomena and collapse processes in the “Latomiae del Paradiso” in Syracuse (Sicily)

The Latomiae (origin: Greek latomia, from laas, las stone plus –tomia tomy ) del Paradiso in Syracuse are Magna Graecia rock quarries, located in the coastal areas of Southern Italy and internationally renowned for their impressive environment. The few historical technical records do not help clarify the events that led to their current configuration since a series of instability phenomena occurred due to decay processes over time. Through a geotechnical back-analysis, this work highlights the failure phenomena, which may have led to the current configuration of the easterly side of the Latomiae del Paradiso. The back-analysis process was carried out by means of numerical modelling, support…

Problemi di conservazione delle camere ipogee in calcarenite nella Fossa della Garofala (Palermo)

La Fossa della Garofala è una stretta valle chiusa da pareti subverticali, incisa dal Torrente Kemonia nella placca calcarenitica che costituisce il sottosuolo di Palermo. Il valore storico monumentale della valle risiede, oltre che nella significatività geologica e geomorfologica del sito, anche nella presenza di cavità ipogeiche artificiali utilizzate dal periodo punico fino al XIX sec. La conservazione nel tempo di questo significativo patrimonio culturale è minacciata da fenomeni di dissesto sempre più frequenti. Il lavoro presenta una caratterizzazione geologica e geotecnica dell’ammasso calcarenitico e propone indirizzi progettuali per gli interventi di consolidamento.

Fossa della Garofala (Palermo): analisi del degrado dell'ipogeo del "Gazebo" e proposte per la conservazione e il recupero

INFLUENZA DEL FABRIC E DEL BONDING SULLO STATO CRITICO E SULLO SNERVAMENTO DELLE CALCARENITI

The research has been devoted to the theoretical interpretation and to the modeling of the mechanical behavior of Quaternary structured soils in the Western South-Western Sicily belonging to the complex calcarenitic-sandy-clayey. After a review about the state of knowledge on the influence of textural characteristics such as fabric and bonding on mechanical behavior, this note presents the results of an experimental analysis by mean of textural identification tests, oedometer tests, triaxial and isotropic tests. For each lithotype critical state conditions and yield strength are defined.

Influenza dei "difetti" strutturali nella formazione di fessure nelle calcareniti

Caratterizzazione geotecnica di tipiche rocce tenere di Palermo

Laser scanner terrestre per la caratterizzazione geotecnica degli ammassi a struttura orientata

Influenza delle anomalie strutturali sulla tensione di danneggiamento e sulla resistenza delle calcareniti

Vengono analizzati i fenomeni di innesco e di propagazione delle fessure in calcareniti non omogenee valutando l’influenza sulla tensione di danneggiamento e sulla resistenza delle anomalie strutturali dovute per lo più o a differenti gradi di cementazione o di addensamento dei grani. L’indagine viene sviluppata utilizzando tecniche non convenzionali di monitoraggio ottico e acustico descritte negli aspetti fondamentali.

Measure of a limestone weathering degree using Laser Scanner.

The weathering degree of the building materials and natural stones is generally quantified as the decrement of some mechanical features that can be measured experimentally by means of compressive tests or point load tests in the laboratory or Schmidt hammer tests carried out in situ. Such destructive or damaging tests are unacceptable in case of cultural heritage since even small amounts of damage must be avoided. This work shows a correlation between Schmidt hammer rebound values and the reflectivity that is detected by means of terrestrial scanner laser; therefore it allows assessing the weathering degree of buildings or stones in situ. The results demonstrate that such an investigation c…

Petrographic and textural characteristics and mechanical behaviour of Sicilian calcarenites

Durability of calcarenitic hypogea in the underground cultural heritage of Palermo (Sicily)

The paper deals with the stability conditions of hypogea, several hundred m 2 wide, dating from the Punic period to the XIX century, dug out of the calcarenitic table that makes up the bedrock of the Plain of Palermo in the Fossa della Garofala. This work concerns the influence that the shape of the hypogea and the characteristics of the lithotypes wields on the instability and decay phenomena taking place, by mean of laboratory tests on the calcarenite and parametric numerical models. The comparison between the numerical models and the actual instability phenomena validated the use of the empirical formula of Hoeck to the mechanical characterization of complex structured rock-mass in soft …