Geotechnical risks in urban areas

Code:
SSD: ICAR/07

 

Learning outcomes: 

Any risk estimation requires the evaluation of three main components: hazard, vulnerability, and exposure. Each component can be evaluated following an approach with an increasing degree of accuracy and complexity. The estimation of geotechnical risks follows the same general approach.

The course deal with the analysis of geotechnical risks at the urban scale, proposing an innovative approach that aims to provide the student with a vision of the security of the built environment.

Four main themes will be faced, corresponding to as many geotechnical risks in urban areas: transient and permanent deformation due to seismic actions, slope instability, instability of underground cavities and excavations.

Each subject will be analysed following the same conceptual frame:

1. Description of the geotechnical problem and related risk terms of triggering causes, propagation, and impact on the built environment. 
2. Simplified approaches for the analysis of the phenomena at urban scale 
3. zoning criteria related to the specific risk for the purposes of emergency planning and land management.
4. possible mitigation measures

The geo-risks taken into consideration will be described not only phenomenologically but also in the light of the concepts of mechanics of Geotechnical Engineering.

Although reference case studies and application exercises will be essentially relevant to the Neapolitan area, the methodological approach is exportable to other geographical contexts.

 

Contents: 

Risk definition

• Risk evaluation: hazard, vulnerability and exposure basic concepts and examples with reference to the geotechnical risks; general framework for risk analysis: the hierarchical approach. Risk assessment and risk mitigation: basic concepts. Possible geotechnical risk in urban areas

 

Transient and permanent effects induced by seismic actions

• Description: Outline of seismogenic and seismic wave propagation mechanisms. Main mechanical effects on soils: non-linear and dissipative behaviour, cyclic resistance. Phenomenological aspects of wave propagation at urban scale.
• Analysis: Outline of the techniques of measurement of mechanical properties in site and laboratory. Analysis techniques and emblematic case studies related to local seismic response and permanent deformative effects (slope instability, liquefaction).
• Zonation: Seismic microzonation: multi-level methodology, Civil Protection guidelines, applications to case studies in the Campania region.

 

 Slope instability

• Description: Stress state in natural slope, influence of water flow and overloads. Landslides classification, influence of meteoric events induced by climate change and impact of human actions. 
• Stability: Hydro mechanical soil characterization, tools for the definition of the surface topography of urban areas, simplified method for the stability analysis at urban scale.
• Zonation: database, zoning criteria based on factor of safety related with different scenario events. Interaction with urban planning and built environment.
• Interventions: mitigation techniques and alert systems.

 

Urban cavities and underground structures: induced settlements and collapse 

• Natural and man made cavities

Description: geometrical features and discontinuities in natural and man-made underground cavities. Risks related to the presence of cavities in urban area. Cavity examples in the Neapolitan underground. 

Stability: simplified approaches for the stability analyses of cavity vaults and pillars.

Zonation: zoning criteria based on safety factor evaluated by simplified approach

Interventions: reinforcement, infill, and other mitigation measures.

• Underground structures

Description: earth pressure: basic concepts; Underground supported excavation: outline of the design and construction techniques. Underground railway infrastructure in Naples: interaction with the built environment and the groundwater regime, examined through case studies. 

Ground induced settlement: simplified approach for the estimation of ground induced settlements

Stability: Rankine earth pressure theory; forces equilibrium-based solutions; role of pore pressures; Limit Equilibrium Methods of analysis.

Interventions: ground improvement and soil impermeabilization techniques.

 

Teaching method: Frontal lessons, in-class exercises

 

Teaching material: Slides of the lessons, journal papers, books

 

Examination procedures: 

Discussion on one or more in-class exercises and on the theoretical and technical aspects debated within the course.