Civil Engineering Foundations and Ground Improvement
English with a size of 388.35 KBTunnel Lining Fundamentals
Purpose of Tunnel Lining
- Support tunnel structure.
- Prevent water ingress.
- Improve durability.
Types of Tunnel Lining
- Concrete
- Shotcrete
- Steel
- Masonry
Sections of Tunnel Lining
- Crown: Top of the tunnel.
- Inverts: Bottom of the tunnel.
- Walls: Sides of the tunnel.
Types of Foundation Footings
- Spread Footing (Pad footing) – Supports a single column.
- Strip Footing (Continuous footing) – Continuous foundation beneath a wall.
- Raft Foundation – Covers the entire building footprint; distributes load on weak soils.
Understanding Foundation Settlement
- Definition: Downward movement due to soil compression.
- Notes:
- Coarse soils: Settlement often ≤ 25 mm (rarely > 50 mm).
- Loose sands below water table: More settlement.
- Clay: Consolidation settlement, slow but significant.
- Excessive differential settlement: Leads to cracks and structural damage.
Ground Treatment Techniques
- Grouting – Injecting cement or chemical fluids under pressure into fissures, pores, and cavities to improve soil strength and reduce seepage.
- Used to stabilize dam foundations, bridge piers, and weak soils.
Vibro-Replacement Method
- Definition: Densification of granular soils and reinforcement of cohesive soils using stone columns formed by vibro-probes.
- Process: A vibroflot creates a hole → coarse backfill is placed → compacted to form stiff stone columns.
- Uses: Improves weak clays, silts, and sands; increases bearing capacity; reduces settlement.
Vibro-Flotation vs. Vibro-Replacement
Aspect | Vibro-Flotation | Vibro-Replacement |
Soil type | Works in coarse granular soils (sands, gravels). | Works in soft clays, silts, weak soils. |
Method | Vibrating probe densifies soil in-situ. | Probe creates columns of compacted coarse backfill. |
Material added | No additional material. | Stone columns inserted. |
Depth | Up to >100 ft in granular soil. | Used for weak, compressible cohesive soils. |
Effect | Densification reduces settlement. | Stiffening + drainage + increased bearing capacity. |
Classification of Dams
Concrete Dams
- Gravity Dam – Stability from weight (e.g., trapezoidal section).
- Arch Dam – Curved, transmits load to abutments.
- Buttress Dam – Sloping slab supported by buttresses.
Earth and Embankment Dams
- Trapezoidal section, impervious clay core, built of natural soil/rock.
- Includes rockfill dams and earthfill dams.
Composite Dams
- Combination of gravity + embankment dam, used when geology varies.
Types of Glaciers
- Continental Glaciers: Cover vast areas (e.g., Antarctica, Greenland).
- Alpine Glaciers: Found in mountain valleys.
- Tidewater Glaciers: Flow into the sea.
Introduction to Hydrogeology
Hydrogeology is the study of water beneath the Earth's surface (groundwater) and its interaction with surface water (streams, springs, glaciers, and wells).
Key Focus Areas:
- Distribution of Water: How water is stored and moves underground.
- Role in Engineering Projects: Ensuring water supply, managing water resources, and mitigating natural hazards.