Università Roma Tre

EXCAVATIONS AND UNDERGROUND CONSTRUCTIONS

1 – Elements of soil mechanics
• Total stress and effective stress, stress path of soil elements.
• Permeability, drained and undrained conditions.
• Stress-strain behaviour of typical soil elements.
• Deformability and strength properties of soils.

2 – Elements of rock mechanics
• Basic concepts of rock material and rock mass, discontinuity (joints, faults).
• Survey and representation of orientation and spacing of discontinuities.
• Mechanical properties of rock materials and discontinuities.
• Quality index and classification systems for the rock mass (particularly, GSI)
• Deformability, strength and permeability of the rock mass.

3 – Excavation methods and support systems for underground structures
• Different types of underground excavations: shallow and deep tunnels, cavern and adits.
• Excavation methods: “cut and cover” and “blind face” excavation.
• “Drill and blast” and “Mechanized excavation”, typical support systems.
• Tunnel Boring Machine (TBM) for rock tunnels.
• “Earth Pressure Balance” and “Slurry Shield” machines for soil tunnels.
• Consolidation works by grouting and ground freezing.

4 – Geotechnical design of slopes and shallow excavations
• Stability analysis of cut and natural slopes.
• Limit equilibrium methods: plane wedges and slices methods.
• Short- and long-term conditions, influence of pore pressure and seismic actions.
• Design of sheet pile walls for cut and cover tunnels.

5 – Geotechnical design of deep tunnels
• In situ stress conditions, influence of topografy and geological stress history.
• Stress and strain around the cross-section of a deep tunnel (plane conditions)
• Stress and strain near the face of the tunnel (three-dimensional conditions)
• Excavation of a tunnel beneath the water table
• Analysis of stability: failure conditions for the face and for the tunnel cross-section.
• Analysis of ground-support interaction: convergence-confinement method
• Loads acting on tunnel support: lining systems for traditional excavation methods and mechanized excavation methods.
• Prediction of the settlement trough caused by tunnel excavation (empirical method) and assessment of possible damage.

Lecture notes prepared by the lecturer and further suggested readings.