Improvment 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 design

Underground Quarrying for Marble: Stability Assessment through Modelling and Monitoring

This paper presents the approach for assessing the stability of underground quarries through the numerical modelling and the monitoring of the stress-strain state of the rock mass and of the support structures. On the basis of the practical experience and long term observation on different case histories, the key issues for a safe and profitable exploitation are given. The procedure is focused on the Candoglia cavern (named Cava Madre), a large mining void due to the exploitation of an high quality marble used for the Milan Cathedral (Duomo di Milano). The importance of the monitoring system for the back analysis of uncertain rock mass parameters and for the operation controls is discussed and emphasized, in order to provide practical design suggestion

PROPERTIES OF NON-CONVENTIONAL WASTE AND GEOMATERIALS FOR REUSE IN EXCAVATION SITES

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

Reinforcement design and control of rock slopes above tunnel portals in Northern Italy

The stability features of slopes located above the portals of tunnels along important roads are here presented, together with two examples for reinforcement and protection works. The investigation phase and the reinforcement works have considered also the purpose of avoiding the interruption of the traffic when this would cause unacceptable consequences. The first case refers about the construction of a portal along a narrow and steep valley in a volcanick rock formation. The control of the vibration of the blasting action has been carried out for the period of the excavation in order to foresee the occurrence of potential dangerous situations. The second is the case of the portal of the East access to the Highway n.10. Even though the adits are protected by two portals, the occurrence of rock and debris falls from the upper part of the mountain could create a dangerous situation. Above the portals the morphology of the slope is characterized by two subvertical rock slopes, which are separated by an intermediate zone of debris material

The influence of the two-component grout on the behaviour of a segmental lining in tunnelling

Filling material is present around the segment lining when a shielded Tunnel Boring Machine is used to excavate a tunnel. The two-component grout is becoming lately one of the most used filling materials. Its mechanical properties evolve over time. Unfortunately, there are not many studies in the literature on the specific mechanical characteristics of these materials. This work presents the results obtained from an extensive laboratory test campaign that allowed to fully characterize the two-component filling material during the setting period. In particular, the values of the stiffness and resistance parameters were obtained over time, where uniaxial compression tests and oedometer tests were carried out. A detailed study of the effect of the presence of the filling material on the behavior of the support system (segmental lining + filling material) was developed for two of the most widespread analytical methods for the analysis of the behavior of tunnels and structures of support: the convergence-confinement method and the Einstein and Schwartz method. Subsequent parametric analyses made it possible to consider the variability of the influencing parameters within the typical variability ranges obtained from the laboratory test campaign or known from the available scientific literature. From the study carried out, it was possible to note that it is necessary to consider the presence of the filling material in the evaluation of the stiffness of the support system, when using the convergence-confinement method to estimate the loads acting on segmental lining. In this regard, it is necessary to have a reliable estimate of the elastic modulus of the filling material in the period of loading of the segmental lining. On the other hand, the presence of the ring of filling material is negligible when evaluating the state of stress of the segmental lining with specific methods capable of considering the rock-support interaction. In particular, adopting the Einstein and Schwartz method, it is possible to define the bending moments and normal forces acting in the support structure, referring to the stiffness parameters of the segmental lining alone

Geophysical–geotechnical methodology for assessing the spatial distribution of glacio‐lacustrine sediments: The case history of Lake Seracchi

Proglacial lakes are distinctive features of deglaciated landscapes and often act as sediment sinks, collecting solid material from subglacial erosion or washout of degla- ciated areas. The solid transport flow, strongly linked to the glaciers and periglacial landforms, may rise due to the rapid changes driven by climate warming, causing deep transformations in the basin hydrology, and even the appearance or disappear- ance of lakes at a decadal timescale. The goal of this study was to present a geophysical–geotechnical approach that inte- grates several techniques, to quantify the sediment distribution in a proglacial lake. A geophysical survey is performed with ground-penetrating radar (GPR) installed on a boat, whereas a time-domain reflectometer (TDR) measures the electrical conductiv- ity and permittivity of the lakebed sediments. Unperturbed samples are collected and analyzed to measure the main geotechnical properties of the sediment: grain-size dis- tribution, plastic limit, and liquid limit. Such properties support the interpretation of the GPR data and the detection of spatial variations of the sediment facies. To validate the proposed methodology, field tests were carried out at Lake Seracchi, the largest lake of the Rutor glacier, Italian Alps. It formed around 1880 because of the recent glacier shrinkage, as chronicled by valuable historical documents. Its greyish waters carry a significant amount of suspended sediment recognized as gla- cial flour, which gradually accumulates on the bottom of the lake. The obtained bathymetry and sediment thickness maps of Lake Seracchi show the strength of the approach: from only a few manual samples, it is possible to extrapo- late the geotechnical properties of interest, such as friction angle or hydraulic con- ductivity, to wider areas, surveyed by the geophysical techniques. This is achieved by investigating the spatial distribution of key geophysical properties linked to the geo- technical properties of interest

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 stability of rock slopes in quarries"

Many ornamental and industrila stone quarries are located along steep slopes or within particular geostructural domains in the Italian Alpine range. The stability of the overburden formations, such as detritic or cohesionless materials, blocky and altered elements or morainic formations, can be compromised by exploitation activities. In other cases there is a natural evolution of the slope, due to singular but diffused phenomena such as block falls, or due to global movements caused by gravity and water interaction. All these facts involve safety aspects not only for the quarrying activities but also because of the possible interference with other nearby structures such as roads, electric power lines and railroads. On the basis of examples some suggestions are given in order to obtain an operative scheme taht is easily adaptable to monitoring and protection of civil excavations of slope

Problems concerning cutting tool performance during TBM work: modelisation and testing of the rock under the action of the tool

In rock excavation engineering, cutting performance prediction plays an important role in machine and cutting tool design. In the past, experimental and theoretical studies on the interaction between rock and TBM tools were conducted for the explanation of the intimate mechanism of rock failure and to obtain knowledge that was able to improve the performances of the TBMs. Nevertheless,, despite several decades of academic rock mechanics and practical rock engineering, there is still a lack of some fundamental knowledge on rock-tool interaction. The objective of this paper is to evaluate a model that predicts the distributed displacement and stresses under a TBM disk, taking into account, in the failure mode, the constitutive law of the rock, the presence of the tunnel head, the amount of the natural stress due to the high overburden, and the forces caused by the TBM disk on the tunnel head. Some laboratory tests were also planned to validate the theoretical results