Fracture Mechanics Characterization of an AnisotropicGeomaterial

Argillites are considered worldwide as potential host rock for high level radioactive waste given the low permeability and strong adsorption potential. However, the excavation of the galleries of a repository would produce a disturbed zone around the boundaries rich of new fractures which may enhance the conductivity of the rock along the gallery axis. Several mine-by experiments have been performed in underground rock labs to investi- gate the features of the disturbed zone. In Mont Terri URL (Kanton Jura, Switzerland) the EZ-B experiment was specifically conceived for the measurement of excavation induced fractures around a small chamber. The host rock of the URL is a particularly compact and resistant argillite, known as the Opalinus Clay (OPA) excavated and OPA samples were subjected to fracture mechanics tests at the rock mechanics lab of IGAG-CNR in Torino, Italy. The tests aimed at the understanding aspects of the fracturing process occurring in OPA of Mont Terri, which may be considered a transversely isotropic geomaterial, whose planes of isotropy coincide with the beddin

A Hydrometeorological Study of Groundwater Level Changes during the {COVID}-19 Lockdown Year (Salento Peninsula, Italy)

The monitoring data of a micrometeorological station in Lecce (Southern Italy, Puglia region, Salento Peninsula) were used with the aim of interpreting the variations in the groundwater level in a shallow aquifer as a function of hydrometeorological forcing. For this scope, the aridity index (AI) was calculated to evaluate the surface-water stress. Although the results indicated a moderate drought during the 2019–2020 hydrological year, a critical situation for the surface hydrological balance in the first quarter of 2020 did not occur. Therefore, the reduction in the groundwater level measured in April can be ascribed to the excessive domestic water consumption that occurred during the lockdown for COVID-19

Cambiamento climatico e protezione delle coste

Le aree costiere sono particolarmente sensibili al cambiamento climatico perché, oltre alle conseguenze legate alle variazioni di temperatura e precipitazioni, subiscono direttamente anche quelle dovute agli aumenti del livello medio del mare e dell'altezza delle onde. Le proiezioni dei modelli climatici prevedono che, entro la fine del XXI secolo, il livello medio del Mediterraneo potrebbe essere più alto di oltre mezzo metro rispetto all'attuale. Un altro effetto del riscaldamento dell'atmosfera terrestre nel Mediterraneo, ossia l'aumento dell'intensità e/o della frequenza di fenomeni meteorologici estremi, come i cicloni con caratteristiche tropicali (noti come medicane), potrebbe inoltre accelerare alcuni processi di erosione costiera. Tutto ciò comporterebbe notevoli impatti ambientali ed economici. Verranno qui illustrati alcuni esempi e discusse le conseguenze sulle opere e sulle attività dell'uomo

Assessment of Specific Yield in Karstified Fractured Rock through the Water-Budget Method

In this note, the Water Budget Method (WBM) is applied to estimate local values of the specific yield of the deep karst aquifer of Salento peninsula. A selection in a period of two years of relevant short precipitation events has been considered and the related localized recharges have been compared to the water table fluctuations measured at two selected wells. The recharge amounts have been corrected by using data of evapotranspiration and soil water storage available from a micrometeorological base. The results are very similar for both the wells and more consistent when the corrections are applied. A discussion involving frequency and apertures of the fractures in the rock mass of the aquifer suggests the effect of the karst dissolution to be dominant in determining these values of the specific yield

Analysis of Interaction of Multiple Cracks Based on Tip Stress Field Using Extended Finite Element Method

A new method is presented to study the interaction of multiple cracks, especially for the areas near crack tips by using the extended finite element method. In order to track the cracks, a new geometric tracking technique is proposed to track enriched elements and nodes along the crack instead of using the narrow band level set method. This allows to accurately determine enriched elements and nodes and calculate enrichment values. A method is proposed for constructing a multicrack matrix, which involves numbering enriched nodes of multiple cracks and solving the global stiffness matrix. In this approach, the stress fields around multiple cracks can be studied. The interaction integral method is employed to study the crack propagation and its direction by calculating the stress intensify factor. The developed model has been coded in MATLAB environment and validated against analytical solutions. The application of the model in the crack interaction study is demonstrated through a number of examples. The results illustrate the influence of the interaction of multiple cracks as they approach each other

Un metodo numerico per la previsione del regime di flusso idraulico in ammassi rocciosi con discontinuita'

Dottorato di ricerca in ingegneria geotecnica. 8. cicloConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Iterative coupling algorithms for large multi-domain problems with the boundary element method

A new Parallel Robin-Robin (P-RR) adaptive Iterative Coupling (IC) algorithm with dynamic relaxation parameters is proposed for the Boundary Element Method (BEM), and relaxation parameters are derived for other existing IC algorithms. The performances of the new algorithm and of the modified existing algorithms are investigated in terms of convergence properties with respect to the number of sub-domains, mesh density, interface mesh conformity and BEM element types. Results show that the number of sub-domains and the refinement level of the mesh are the two dominant factors affecting the performances of the considered algorithms. The proposed P-RR algorithm shows the best overall convergence behavior for the tested large problems, thanks to its effectiveness in handling complex boundary conditions and large number of sub-domains, thus resulting very promising for efficient parallel BEM computing and large coupling problems

Experimental tests for the assessment of the shear strength of marble waste dumps

The large dumps of waste material called ravaneti from marble quarrying activities in Alpi Apuane basin are distinguished features of the local landscape. They are strongly heterogeneous, never compacted and frequently subject to local instabilities. The access roads to the marble quarries cross the dumps; therefore, it is concern of the local authorities to hinder such phenomena. In this respect it is of paramount importance to evaluate the shear strength of the material comprising the dumps at the proper scale. In this note, the results of in-situ direct shear and tilt tests on samples of metric size are illustrated, together with the interpretation according to a strength criterion relative to rockfills. The results of a series of lab tests on the finer fraction of the waste material are also described and interpreted. Finally, qualitative considerations on the local and global stability of the waste dumps, related to their shear strength, are reported