Construction Principles CSP115B - Week 5 Dams

Construction Principles CSP115B (Week 5 - Dams)

• Dam engineering is a branch of civil engineering
• It involves the design, construction, and operation of dams which are structures built across rivers or streams to impound water.
• Dams are crucial infrastructure for managing water resources; they serve diverse purposes.
• Dams are used for water storage, flood control, irrigation, and hydroelectric power generation
• Dams play a vital role in modern infrastructure
• Dams require balancing resource management with environmental and social considerations
• Proper planning and management are essential for maximizing benefits and minimizing negative impacts.

Key Considerations in Dam Engineering

• Safety: Dams must be designed to withstand extreme weather events (floods and earthquakes).
• Water Quality: Dams must maintain good water quality, preventing contamination and minimizing sedimentation.
• Environmental Impact: Dams must minimize environmental impact, protecting habitats and preventing erosion.
• Cost and Economics: Dams need to be cost-effective and economically viable.

South Africa's Largest Dams (by Capacity)

• Gariep: 5,341 million m³
• Sterkfontein: 2,617 million m³
• Pongolapoort: 2,446 million m³
• Vanderkloof: 3,172 million m³
• Vaal: 2,604 million m³

Feasibility Study - Site Selection

• Width and shape of the site (valley; wide open area)
• Storage capacity (yield of catchments and use)
• Foundations
• Availability of materials for construction
• Spillway potential for non-overflow dams
• Prevailing wind direction

Feasibility Study - Site Investigation

• Topography
• Geological evaluation (drilling, trenching, shafts, and surface investigations) of in-situ ground (soil or rock)
• Permeability test (boreholes)
• Hydraulic model tests (large dams)
• Evaluation of existing dams of similar design

Feasibility Study - Detailed Investigation Considerations

• Water supply (checking availability)
• Floodlines and stream flows (potential of damage to surrounding properties)
• Location, geological factor, and availability of material
• Sedimentation rates
• Forces, water pressure, wind loads, waves, and soil pressure

Feasibility Study - Detailed Investigation Considerations (Cont'd)

• Environmental factors, natural scenery, and ecology must be improved.
• Construction period (careful planning of construction activities).
• Lifespan of the storage unit (economic viability)
• Evaporation (water loss due to evaporation)
• Wind, tide and wave action
• Earthquake resistance (avoid areas prone to earthquakes)

A2R006 – Bospoort Dam (Layout Sketch)

• Layout including earth fill walls, weather station, purification works, and river gauging station.
• Labyrinth spillway

Types of Dams

• Embankment Dams: Earth, rock fill
• Concrete Dams: Arch, multiple arch, buttress, masonry, gravity
• Types explained by their construction materials and methods

Importance of Dams

• Water Supply: Ensures a steady supply of water during dry periods.
• Flood Control: Regulates river flow to prevent downstream flooding.
• Hydroelectric Power: Generates renewable energy by harnessing flowing water.
• Irrigation: Supports agriculture and food production.
• Recreation and Tourism: Provides opportunities for various recreational activities.

Embankment Dams Design (Components)

• Core wall
• Cut-off wall
• Crest (top of embankment)
• Earth embankment
• Filter zones
• Transition filters
• Internal drain
• Freeboard
• Overfall/overflow/overspill
• Rip-rap
• Spillway
• Toe drain

Embankment Dams Design (Design Components)

• Permeability
• Stability
• Compression
• Washing of fines
• Availability of construction materials.

Concrete Dams Design (Components)

• Gravity Dam
• Arch Dam
• Buttress Dams
• Masonry Dams

Challenges Faced During Dam Construction

• Geological uncertainties (unstable foundations, water seepage, landslides)
• Environmental concerns (habitat disruption, ecosystem alteration, wildlife impacts)
• Water management (fluctuations, erosion, quality)
• Logistical challenges (transport in remote areas).

Challenges Faced During Dam Construction (Cont'd)

• Safety risks (accidents, injuries, fatalities, during excavation, blasting, placement)
• Cost overruns (unforeseen conditions, design changes, delays)
• Community displacement
• Seismic activity

Challenges Faced During Dam Construction (Cont'd)

• Material Selection (withstanding stresses; dam's operation)
• Regulatory Compliance (environmental regulations, safety regulations, water quality regulations)

Technical Challenges

• Foundation Design: Stable foundation to transfer dam weight
• Concrete Placement: Ensuring quality and durability in various weather conditions.
• Waterproofing: Preventing seepage and leakage to ensure safety and stability.
• Drainage: Effective drainage systems to avoid erosion and water accumulation

Technical Challenges (Cont'd)

• Instrumentation and Monitoring: Identifying and rectifying problems to ensure safety and reliability.

Addressing Challenges

• Careful Planning: Thorough feasibility studies to identify risks and challenges.
• Experienced Team: Experienced engineers, contractors, project managers.
• Innovative Solutions: Use of advanced materials and construction techniques.
• Community Engagement: Minimize social impacts.
• Regulatory Compliance: Compliance with regulations.

Water Conservation

• Scarcity
• Rising population
• Climate change
• Water consumption (seawater, greywater, groundwater)