Tunnel static behavior assessed by a probabilistic approach to the back-analysis

Problem statement: The steps of the validation procedure of the project of a tunnel are briefly illustrated in this study, starting from the geological and structural surveys on the excavation walls and the measurement of the physical and mechanical parameters during the excavation works. Unfortunately, however, the knowledge of the rock mass, which is fundamental to the project, is usually approximate before the study is started. This knowledge improves considerably once construction of the tunnel is started, when it is possible to have direct access to the rock and analyze its behavior in relation to the excavation and support works. Approach: The measurement of displacements and stresses in the rock mass and in the support structures represents a different methodology for the evaluation of the Geotechnical characteristics of a rock mass and therefore also of the support work conditions. To correctly interpret the measurements it is necessary to make use of a more complex procedure, called back-analysis, that, starting from an estimation of the unknown parameters of the rock mass obtained through a preliminary characterization, integrated and modified by sampling of the rock mass during the construction stage and by the performed stress and displacement measurements, is able to define the unknown parameters of the rock mass. Results and Conclusion: Back-analysis in engineering in the rock field occurs, however, in an uncertainty context, which complicates the problem. The preliminary estimation of the Geotechnical characteristics of the rock mass has in fact a degree of reliability that is a function of the intensity of the preliminary investigations. The performed measurements present a certain precision in relation to the various typologies of error that can occur. The final result of the back-analysis therefore also consists in the definition of the Geotechnical parameters of the rock mass that are considered to be of influence in the problem under examination, with a certain reliability and precision that is obviously greater than that relative to the initial estimation of the same parameters. The purpose of this study is to present a global approach to back-analysis in a probabilistic context that is aimed to obtain a reliable calibration of the parameters of the rock mass that are necessary to study the behavior of the support structure

Identificazione del rischio per fenomeni di caduta massi

La nota riferisce sulle modalità descrittive e di quantificazione del rischio in relazione ad eventi franosi localizzati, quali i fenomeni di caduta massi. Ponendo come base il riconoscimento delle caratteristiche geostrutturali e morfologcihe del versante, sono inquadrate le procedure per valutare il passaggio dalle condizioni di ricorrenza dei fenomeni al danno potenziale. Il rimando ad un esempio applicativo denota quali siano i margini di incertezza connessi allo studio di fenomeni per loro natura puntuali e discontinui

Analisi geomeccanoiche per la stabilità degli scavi in sotterraneo della Pietra del Cardoso

L'articolo decsrive sperimentazione, caratterizzazione e modellazione relative alla pietra del Cardoso, nella quale sono impostate cave sia a giorno sia in ostterraneo. In particolare lo studio è stato rivolto proprio al passaggio in sotterraneo della coltivazione

design of reinforced ground embankments used for rockfall protection

Abstract. The prediction of the effects of rockfall on passive protection structures, such as reinforced ground embankments, is a very complex task and, for this reason, both full-scale tests and numerical dynamic modelling are essential. A systematic set of numerical FEM models, developed in the dynamic field, has been implemented in this work to evaluate the conditions of an embankment that has been subjected to the impact of rock blocks of various sizes at different speeds. These analyses have permitted design charts to be obtained. Furthermore, a simplified analytical approach, based on an equilibrium analysis, has been proposed and its results are compared with numerical data in order to assess its feasibility. A good correspondence between the results has been obtained

Overburden management in open pits: options and limits in large limestone quarries

This is the 'In press corrected proof' version. The final version is available from Elsevier via the DOI in this recordThe management of overburden is an important task in open pit exploitations. Site topography and morphology as well as geological and geotechnical properties of natural and remoulded materials are the most important factors affecting the disposal phase. Economic and environmental requirements must be followed in order to achieve the best reclamation results, keeping into account site constraints such as slope stability, hauling and dumping issues, and interactions with groundwater. This paper deals with the above mentioned issues, illustrating a rational approach applied on the case of a large limestone quarry where the thickness of the overburden is relevant and the spoil material has to be dumped in a flooded pit. The proposed multidisciplinary approach led to the selection of most suitable methods for excavation, transportation and disposal. The selection was based on a detailed laboratory and site characterisation that defined favorable and adverse factors to be considered during the preliminary study of a large quarrying project.Thanks are due to Mr G. Torchio for the graphics of the 3D simulation of overburden disposal from fixed discharge points. Special and extended thanks are due to the technical and support staff of CCB in Gaurain (Belgium) and Italcementi CGT in Bergamo (Italy), which supported part of this research by means of a research contract with Politecnico of Turin, DIATI (coordinator A. Godio

Characterisation of geomaterials and non-conventional waste streams for their reuse as engineered materials

This is the author accepted manuscriptReusing bulk volumes of waste material is a requirement often encountered in mining and construction activities involving excavations. Spoils produced from these activities typically show high variability in terms of properties and behaviour, due to the local geology, adopted excavation method and further spoil treatments. A procedure for classifying the spoil from tunnelling was proposed in order to correlate ground type, possible muck destination and treatment type. With a similar approach in industrial and related sectors, the reuse of non-conventional materials (i.e. wooden chips, fragments, granulates, micronized glass, residual out of shape from manufacturing processes or coming from selection of other waste) has a great relevance as it is accompanied by savings in disposal costs and in the sourcing of raw materials. Characterisation tests derived from geotechnical engineering can support the assessment of the physical and mechanical properties of non-conventional materials, creating a feedback loop encompassing raw material description, required treatments, and possible utilisations as engineered materials. This paper describes the possible screening tests and treatment options for material recycling in the framework of a modified spoil classification system

Properties of non-conventional waste and geomaterials for reuse in excavation sites

This is the author accepted manuscript.Reuse and recycling of waste material from excavation and mining/quarrying activities is a global issue that received significant attention in the last decades. The links among local geology, excavation methods, spoil treatment and strategies for recycle have been identified as unavoidable in terms of early physical, chemical and mechanical characterisation of spoils. The emergence of a range of industrial waste streams and the environmental, economic and technical considerations arising from their recycle and reuse still need a comprehensive technical and validated procedure for acceptance. This paper describes the screening tests and treatment options for material recycling in the framework of an original spoil classification system, also for specific applications, such as drainage layers, covering of dumps, rehabilitation of abandoned sites. The experience learnt by the Authors from the development of suitable methodologies for characterisation and management of spoil waste can be extended to other waste such as glass waste, gypsum, rockwool, glasswool, granulates, chipping particles, polymeric cuttings which show similarities with soils and geomaterials in terms of ‘bulk behaviour

Un esempio di protezione di portali di gallerie autostradali: il ruolo delle indagini e dei monitoraggi

La nota illustra gli interventi realizzati a protezione delle strutture autostradali poste a ridosso del promontorio di Siestro, a Ventimiglia. In tale contesto la necessità di conseguire una pressoché totale eliminazione delle condizioni di rischio per l'utenza ha comportato una fase di studio preparatoria basata su indagini in sito, la scelta di interventi efficaci e il monitoraggio delle condizioni strutturali del versante

Improvements of safety conditions of unstable rock slopes through the use of explosives

The paper discusses operations aimed at creating a safer natural or man made rock slope by artificially inducing the displacement of unstable elements by blasting. A detailed analysis of the problems with the use of explosives present when conducting these activities is carried out focusing on the advantages and disadvantages of this technology. The results of two examples of demolition of instable rock elements are presented and discussed thus providing suggestions for future blasting designs