QuaRRi: a new methodology for rock-fall risk analysis and management in quarry exploitation

Rockfall is one of the most critical geological events that can affect quarrying activities. Nevertheless, few tools are currently available to help designers and managers correctly define the risk conditions and quantify the advantages, in terms of workers' safety and quarry management, that can be obtained using suitable prevention devices. For this reason it is necessary to evaluate the various parameters that are involved, and to define the most important and which have the greatest influence on rock-fall phenomena, taking into account the Prevention through Design approach. A risk evaluation systemwhich is able to support decision makers in the critical rockfall risk assessment phase, and offer decision makers the updated information that is necessary for a continuous and dynamic operation design during exploitation activities is here presented and discusse

Numerical models for the design and construction of new underground structures at CERN (HL-LHC), Point 5

The Large Hadron Collider (LHC) is the latest, most powerful, world’s largest underground particle accelerator realized on the CERN site. High-Luminosity LHC (HL-LHC) is a new project aimed to upgrade the LHC, at Point 1 (ATLAS in Switzerland) and Point 5 (CMS in France) in order to enhance scientific progress. This paper describes the design and construction issues developed at the Point 5 for the new underground structures, located near the existing LHC tunnel. The project requires new technical infrastructure: an additional shaft with a 12 m-diameter and 60 m-height, cavern with 270 m2 cross-section, approximately 500 meters of tunnels connected to the LHC tunnel, vertical linkage cores and additional technical buildings at the surface. The geological ground model of this site lies in an area covered by Quaternary moraine with two independent aquifers. The bedrock of Molasse comprises sub-horizontal lenses of heterogeneous sedimentary rock, that is known to locally retain hydrocarbons and to have a swelling behaviour. In order to investigate the heterogeneous behaviour of the rock mass composed of several layers with different strengths, numerical calculations have been performed, under a 2D plane strain condition with RS2 9.0 FEM-software.. The purpose of using the software was to design both the rock-supports and the concrete inner lining for the tunnels and the shaft. Data from a comprehensive monitoring system with pre-defined threshold values was compared to the 2D FEM results, confirming the importance of the observational method to verify the assumptions used in the numerical modelling. The execution of the underground works started in April 2018. The excavation of the main un-derground works has been successfully completed without any critical impact on the nearby ex-isting underground structures. The completion of the works is scheduled for September 2022

Quantification and management of rockfall risk in opencast quarrying activities

Rockfalls during quarrying activities are among the most critical risks associated with the various kinds of geological instabilities. Nevertheless, very few tools are available to help designers and managers correctly define these risk conditions in a rational way and to quantify the advantages that can be obtained using suitable prevention measures. For this purpose, taking into account the ‘‘Prevention through Design'' approach, it is necessary to weigh the various parameters that are involved and to define the most important factors, that is, the ones that have the most influence on rockfall phenomena. A risk evaluation system that is able to support decision makers in the critical rockfall risk assessment phase and offer them the updated information that is necessary for a continuous and dynamic operation design during exploitation activities is presented and discussed her

The Ceneri Base Tunnel: Construction Experience with the Southern Portion of the Flat Railway Line Crossing the Swiss Alps

This paper summarizes the experience that was gained during the construction of the 15.4 km long Ceneri Base Tunnel (CBT), which is the southern part of the flat railway line crossing the Swiss Alps from north to south. The project consisted of a twin tube with a diameter of 9 m interconnected by cross-passages, each 325 m long. In the middle of the alignment and at its southern end, large caverns were excavated for logistical and operational requirements. The total excavation length amounted to approximately 40 km. The tunnel crossed Alpine rock formations comprising a variety of rock typologies and several fault zones. The maximum overburden amounted to 850 m. The excavation of the main tunnels and of the cross-passages was executed by means of drill-and-blast (D&B) excavation. The support consisted of bolts, meshes, fiber-reinforced shotcrete and, when required, steel ribs. A gripper tunnel boring machine (TBM) was used in order to excavate the access tunnel. The high overburden caused squeezing rock conditions, which are characterized by large anisotropic convergences when crossing weaker rock formations. The latter required the installation of a deformable support. At the north portal, the tunnel (with an enlarged cross-section) passed underneath the A2 Swiss highway (the major road axis connecting the north and south of Switzerland) at a small overburden and through soft ground. Vertical and sub-horizontal jet grouting in combination with partial-face excavation was successfully implemented in order to limit the surface settlements. The south portal was located in a dense urban area. The excavation from the south portal included an approximately 220 m long cut-and-cover tunnel, followed by about 300 m of D&B excavation in a bad rock formation. The very low overburden, poor rock quality, and demanding crossing with an existing road tunnel (at a vertical distance of only 4 m) required special excavation methods through reduced sectors and special blasting techniques in order to limit the blast-induced vibrations. The application of a comprehensive risk management procedure, the execution of an intensive surface survey, and the adaptability of the tunnel design to the encountered geological conditions allowed the successful completion of the excavation works. Keywords: Deep and long tunnel, Difficult ground conditions, Support design, Risk management, Tunnel monitoring, Large caverns, Low overburden, Overpass tunnel, Numerical analysis, Excavation in urban are

CERN, HL-LHC Project: numerical modelling and design challenges for the new underground facilities at Point 5

The most powerful underground particle accelerator, known as Large Hadron Collider (LHC), is located at CERN on the border between Switzerland and France. The High-Luminosity (HL-LHC) Project will increase existing facilities with new underground and shallow structures at Point 1 (ATLAS, Switzerland) and Point 5 (CMS, France). The new underground structures include a shaft, a wide cavern, 500 meters of galleries and some vertical linkage cores. This paper presents the main challenges of the Project at Point 5 describing the design and construction issues encountered for the underground structures, together with the key role of the numerical modelling in the design. The main challenges of the construction were related to the following: i) meeting the tight schedule of design and construction ii) defining design criteria i.e. calculating expected excavation-induced vibrations and minimizing the disturbance effects on the LHC where experiments were in progress; iii) excavating within a complex rock mass with several known challenging characteristics; iv) assessing the potential impact of the excavation works on the nearby existing underground structures. The excavation of the main underground works was successfully completed without any critical impact on the nearby existing underground structures. The construction phase is on track for completion within the stipulated contractual Construction Programme. The completion of the entire works is scheduled for September 2022

LE NUOVE OPERE SOTTERRANEE PRESSO IL CERN (HL-HLC), PUNTO 5: SFIDE PROGETTUALI ED ESECUTIVE

Il Large Hadron Collider (LHC) è il più grande acceleratore di particelle situato presso il CERN di Ginevra. Trattasi di una struttura ad anello di 27 km, realizzata alla profondità di 100 m e dotata di 8 punti sperimentali in sotterraneo. In tale contesto, l’High-Luminosity (HL-LHC) è un recente progetto finalizzato al miglioramento dell’esistente acceleratore di adroni (LHC) che richiede nuove strutture sotterranee presso i punti sperimentali 1 (Svizzera) e 5 (Francia). Il presente articolo illustra le principali sfide incontrate nella progettazione e costruzione delle strutture sotterranee presso il Punto 5. Al fine di analizzare il comportamento tenso-deformativo delle differenti litologie riscontrate, la progettazione si è avvalsa di modelli numerici agli elementi finiti, fondamentali per riprodurre adeguatamente l’avanzamento delle fasi di scavo, valutare le conseguenze sulle adiacenti strutture esistenti e dimensionare i sostegni e rivestimenti. Ad oggi, le principali opere sotterranee sono state realizzate con successo e senza criticità. Il termine dei lavori è previsto per il 2022