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

Unsaturated sand in the stability of the cuesta of the Temple of Hera (Agrigento)

In the Valle dei Templi in Agrigento seven Doric temples stand lengthwise the crest of a rigid calcarenite cuesta over a layer of carbonate sand which lies along a thick stratum of clays. The environment is highly prone to landslides since topplings of calcarenite blocks often occur. The rock slopes are moving back and the slope edge draw near to the foundation of the Temple of Hera Lacinia contributing to increase their perilous condition. To assess the role of unsaturated sands in the instability processes, after the compositional and textural analysis of the material, direct shear tests and oedometer tests have been carried out on sand samples initially at the natural state, with low or very low values of natural water content, and finally at full saturation. The mechanical behaviour of sands seems one of the main causes of the instability influenced by the presence of an open metastable structure, which develops through bonding mechanisms generated via suctions and/or through cementing material such as clay or salts

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 monuments. This note presents results of research about relationship between the index (I) and the hammer Schmidt rebound r both on stone surfaces and on historical artifacts characterized by different levels of alteration

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

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

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 inmany areas of southwestern Sicily, are characterized by sudden changes in their deformability, strength and permeability characteristics. The geotechnical identification, bymeans of computerized axial tomography and thin section petrographic analysis suggested a subdivision of these two calcarenites into five lithotypes as a function of their structural configuration. These calcarenites are metastable rockswhosemechanical behaviour depends on the fabric and bonding. Oedometer, triaxial and isotropic tests were conducted to analyzed interparticle bonding and/or fabric effects on themechanical behaviours. For each lithotype the yield limitwas defined and three distinct behavioural patterns were identified as a function of the confining stress level: 1) an initial linear elastic behaviour up to the yielding strength, 2) a yielding phase characterized by a strain-softening response, 3) a final phase of the destructured material. At yield state, bonding is the major factor contributing to the soil strength, while the effect of fabric comes into play at post-yield stress state. For the assessment of the yielding conditions the yield stress values obtained from various stress-paths were taken into accoun

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 rock