Geological Hazards: Understanding and Mitigation Strategies

Diapirs: Geological Risks and Mitigation

When sedimentary rock salt material reaches a certain temperature, it behaves like a fluid and tends to rise. This process can cause folded sedimentary materials and salt to reach the surface, a phenomenon known as diapirism. Saline materials are economically significant.

Measures Against Diapirs:

• Preventive Measures:
  • Conduct adequate geological studies to understand their evolution.
  • Implement effective territory planning.
• Corrective Measures:
  • Inject solid materials into areas where they might dissolve.
  • Monitor and curb the development of the diapir.

Expansive Soils: Characteristics and Management

Expansive soils are composed of rocks that can easily absorb and release water (e.g., clay, loam). These rocks are very abundant, forming approximately 35% of the Earth's surface layer. Therefore, it is crucial to consider them during construction. When these soils lose water, they crack; when they absorb water, they swell significantly. These are the primary risks.

Measures for Expansive Soils:

• Conduct comprehensive geological studies.
• Forecasting: Climatic, hydrological, and topographical studies.
• Develop detailed risk maps.
• Prevention: Implement technical solutions (e.g., drainage or adding calcium to the soil).

Slope Movements: Types, Causes, and Mitigation

Slope movements are displacements of both bound and unbound materials on slopes, primarily driven by gravity. The presence of water, in varying amounts, significantly encourages these movements. Landslides are common in our country and can often be anticipated and prevented.

Types of Slope Movements:

• Landslide: When an entire layer of soil moves on solid material.
• Detachment: When rock fragments leap across a slope.
• Downhill Creep: Loose materials that move very slowly on a sloping surface.
• Avalanche: Very rapid movement of loose material, often mixed with water and snow.
• Flow: Material movements without cohesion, which behave as fluids.

Factors Determining Slope Movements:

• Relief: The slope angle.
• Lithology: Rock type and structure.

Triggers:

External factors that destabilize a hillside by modifying existing conditions include:

• Climatic conditions.
• Hydrological changes.
• Undermining or natural erosion at the foot of the slope.
• Seismic movements.
• Human actions (e.g., excavations, changes in land use).

Consequences:

Direct effects on life and property, and interference with other systems.

Actions Against Landslides:

• Preventive Measures:
  • Conduct thorough geological studies.
  • Develop comprehensive risk maps (studying determinants and triggers).
  • Implement territory planning to prevent people from settling in high-risk areas.
• Corrective Measures:
  • Drainage works: Reducing runoff, erosion, and the swelling of clays. This includes constructing gutters, galleries, and wells.
  • Construction of containment structures: Using concrete walls, nets, and anchors to fix unstable materials to the substrate.
  • Modify the slope profile by filling the bottom.
  • Improve planting and reforestation of the land.

Subsidence and Collapse: Causes and Mitigation

These are ground movements. Subsidence is a slow and progressive sinking of the ground, whereas collapses are rapid and sudden. Both can be natural or anthropogenically induced.

Causes:

• Natural processes: Include karstic (caustic) and tectonic activities.
• Induced causes: Include fluid extraction (water, oil), compaction, mining, and large underground excavations.

Consequences:

• Damage to civil works and construction.
• Land inundation by water.
• Contamination of groundwater through fissures.

Measures Against Collapse and Subsidence:

• Preventive Measures:
  • Develop risk maps considering the lithology.
  • Implement territory planning.
• Structural Preventive Measures:
  • Construct suitable buildings.
  • Improve terrain.