The course deals with the issues related to the design and construction of underground works in soils and rocks, in the civil and mining sectors (such as underground parking lots, urban and road tunnels, underground stations, hydroelectric caverns, quarries and underground mines, service shafts and access tunnels to underground works, access ramps to mineral voids, mining exploitation panels). Furthermore, the fundamental concepts of Mining (the exploitation techniques for above ground and underground mines, the typical scheme of an open quarry and an underground mine are also given.

The course aims to give basic knowledge and practical techniques for the planning, design and construction of the main underground civil and mining works. Students will learn how to dimension underground works and their supports, in order to ensure their stability. Students will be able to evaluate the techniques necessary for their realization and to define the most important strategies for extracting the minerals from an open quarry and an underground mine.

The fundamentals of applied geology, geomechanics, structural mechanics and excavation engineering are required.

1. Introduction to underground works Outline of demographic development in the urban environment. Types and use of underground works. Characteristics and problems of an underground work. Advantages and disadvantages of an underground work. The economic evaluation of environmental benefits. 2. Stability of the underground voids The shallow excavations to house the underground work. The stability of the side walls of the excavation in the absence of supporting structures. The use of supporting structures for the realization of shallow excavations in soils. Diaphragm functioning mechanism. The contrast structures of the diaphragms. Definition of the geomechanical parameters of the rock mass starting from the geomechanical classifications. Stress state around an underground rock cavity. Simplified methods for analyzing stresses around an underground cavity in rock. Use of diagrams and tables to identify the stress state on the contour of the cavity. Detailed analysis of the stress state around an underground cavity. The convergence-confinement method. Analysis of the loads induced on the supporting structures using the convergence-confinement method. Effects of the presence of supports and reinforcements on the stress distribution. Plastic zones development around the cavities. Effect of the original stress state on the static behavior of an underground cavity. 3. Construction methods The large shallow cavities (underground car parks and underground stations). The Cut and Cover Method. Construction methods of caverns and large underground cavities. Caverns in rock: top heading attack and lowering of the foot. Shaft construction methods. 4. Methods for the analysis of the stability of an underground work Finite element methods for simulating diaphragm behavior. The dimensioning of the diaphragms (thickness and steel rod reinforcement). Determination of induced displacements on the surface. Effects on adjacent buildings. Numerical methods for the analysis of the stability of an underground work: continuous and discontinuous methods. Advantages and disadvantages. The finite element (FEM) and finite difference (FDM) method. Mathematical principles of numerical methods. Procedure for the construction of a numerical model: the boundary conditions, the mesh definition, the insertion of the rock mass parameters, the initialization of the lithostatic stress, the simulation of the excavation steps. 5. Reinforcement and support structures Micropiles and jet-grouting comb: Technological aspects and dimensioning calculations. The concept of the equivalent bulkhead. The effect of tie rods on the diaphragm behavior. The support structures of underground cavities. Dimensioning of concrete and steel support structures. Dimensioning of passive bolts and tie rods. Stress verifications inside the bolt and on the lateral surface. Dimensioning of anchor bulb and tie rod strands. 6. Mining General principles of mining. Typical schemes of open quarries and underground mines. The exploitation methods adopted in the mines. Stability analysis of mining voids. Exploration and mining works. Preliminary investigations, the estimate of the amount of mineral in a deposit. The typical schemes of a quarry and a mine. Issues related to mining: useful mineral loss, dilution, yield. The subsidence of the surface as a result of mining.

The exercises will focus on some aspects addressed during the course and more specifically on the stability analysis of large cavities in rock with numerical calculation methods, on the dimensioning of reinforcement interventions in the crown and on the side walls of a rock cavern, on the calculation and dimensioning using the finite element method of a concrete diaphragm, on the dimensioning of the tie rod bulb, on the sizing of an underground concrete structure. Furthermore, specific exercises will be carried out on the dimensioning of underground mining works, on the evaluation of the useful resources of a deposit, on the problems related to the subsidence induced by underground mining activities.

a) Slide presentations and other documentary material used during the lessons; b) In-depth texts reported gradually for each topic, available in the library of the DIATI Department or freely on internet.

Slides; Video lezioni dell’anno corrente;

Modalità di esame: Prova orale obbligatoria; Elaborato scritto prodotto in gruppo;

Exam: Compulsory oral exam; Group essay;

... The exam is in written form (duration 2 hours). The following oral exam concerns the presentation and discussion of the reports developed in groups by the students during the course and the presentation of an in-depth report on a specific theme of the program, also carried out in groups. The vote will be defined considering the result of the written exam (weight 65 %), the evaluation of the reports on the exercises and the presentation and discussion (weight 25%) and the evaluation of the in-depth report and its presentation (weight 10%).

Gli studenti e le studentesse con disabilità o con Disturbi Specifici di Apprendimento (DSA), oltre alla segnalazione tramite procedura informatizzata, sono invitati a comunicare anche direttamente al/la docente titolare dell'insegnamento, con un preavviso non inferiore ad una settimana dall'avvio della sessione d'esame, gli strumenti compensativi concordati con l'Unità Special Needs, al fine di permettere al/la docente la declinazione più idonea in riferimento alla specifica tipologia di esame.