CSP115B - Week 5 Dams PDF

Construction Principles CSP115B (Week 5 – Dams) Introduction Dam engineering is a branch of civil engineering that deals with the design, construction, and operation of dams, which are structures built across a river or stream to impound water. Dams are crucial infrastructures built to mana...

Construction Principles CSP115B (Week 5 – Dams) Introduction Dam engineering is a branch of civil engineering that deals with the design, construction, and operation of dams, which are structures built across a river or stream to impound water. Dams are crucial infrastructures built to manage water resources. They serve multiple purposes, including water storage, flood control, irrigation, and hydroelectric power generation. Dams play a vital role in modern infrastructure, balancing the need for resource management with environmental and social considerations. Proper planning and management are essential to maximize benefits and minimize negative impacts. Faculty of Engineering and the Built Environment Department of Civil Engineering Key Considerations in Dam Engineering When designing and constructing a dam, engineers must consider several key factors, including: 1) Safety: The dam must be designed to withstand extreme weather events, such as floods and earthquakes. 2) Water quality: The dam must be designed to maintain good water quality, including minimizing sedimentation and preventing contamination. 3) Environmental impact: The dam must be designed to minimize its impact on the surrounding environment, including protecting habitats and preventing erosion. 4) Cost and economics: The dam must be designed to be cost-effective and economically viable. Faculty of Engineering and the Built Environment Department of Civil Engineering South Africa’s Largest Dams (in capacity) Vanderkloof 3 172 million m³ Gariep 5 341 million m³ Pongolapoort 2 446 million m³ Sterkfontein 2 617 million m³ Vaal 2 604 million m³ Faculty of Engineering and the Built Environment Department of Civil Engineering Feasibility Study Site Selection: Width and shape of the site (valley; wide open area) Storage capacity (yield of catchments and use) Foundations (determine height of dam) Availability of materials for construction Spillway potential for non-overflow dams Prevailing wind direction. Faculty of Engineering and the Built Environment Department of Civil Engineering Feasibility Study (Cont’d) Site Investigation: Topography Geological evaluation (drilling, trenching, shafts and surface investigations) of the “in-situ” ground (soil or rock) Permeability test (boreholes) Hydraulic model tests (large dams) Evaluation of existing dams of similar design Faculty of Engineering and the Built Environment Department of Civil Engineering Feasibility Study (Cont’d) Detailed Investigation Considerations: Water supply: checking the availability of water Floodlines and stream flows, potential of damage to surrounding properties Location, geological factor and availability of material Sedimentation rates, may silt up and make reservoir shallower Forces, water pressure, wind loads, waves and soil pressure Faculty of Engineering and the Built Environment Department of Civil Engineering Feasibility Study (Cont’d) Detailed Investigation Considerations: 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 losses due to evaporation Wind, tide and wave action, wind load on the dam Earthquake resistance, avoid areas prone to earthquakes where possible Faculty of Engineering and the Built Environment Department of Civil Engineering Weather station River gauging station River Gauging Station Faculty of Engineering and the Built Environment Department of Civil Engineering Evaporation Pans Faculty of Engineering and the Built Environment Department of Civil Engineering Types of Dams 1. Embankment dams Earth dams Rock fill dams 2. Concrete dams Arch dams Multiple arch dams Buttress dams Masonry dams Gravity dams Or a combination… Faculty of Engineering and the Built Environment Department of Civil Engineering Types of Dams 1. Gravity Dams Constructed from concrete or stone, these rely on their weight to hold back water. The Hoover Dam is a famous example. 2. Arch Dams Curved in shape, they transfer the water pressure to the valley walls. The Glen Canyon Dam is an example. 3. Embankment Dams Made from earth or rock, these are the most common type due to their cost-effectiveness and suitability for a variety of locations. Faculty of Engineering and the Built Environment Department of Civil Engineering Types of Dams 4. Buttress Dams Feature a sloping deck supported by triangular buttresses, reducing the amount of material needed. 5. Diversion Dams Redirect water to canals or pipelines instead of creating a reservoir, used mainly for irrigation. 6. Hydraulic Fill Dams These dams are constructed using a mixture of soil and water, which is pumped into place to create the dam. Faculty of Engineering and the Built Environment Department of Civil Engineering Importance of Dams 1. Water Supply: Dams store water for domestic, agricultural, and industrial use, ensuring a steady supply even during dry periods. 2. Flood Control: By regulating river flow, dams help prevent downstream flooding, protecting communities and agricultural areas. 3. Hydroelectric Power: Dams generate renewable energy by harnessing the power of flowing water to produce electricity. 4. Irrigation: Stored water is used to irrigate crops, supporting agriculture and food production. 5. Recreation and Tourism: Many dams create reservoirs that offer recreational activities like boating, fishing, and tourism opportunities. Faculty of Engineering and the Built Environment Department of Civil Engineering Embankment Dams Design (Cont’d) 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 Faculty of Engineering and the Built Environment Department of Civil Engineering Embankment Dams Faculty of Engineering and the Built Environment Department of Civil Engineering Embankment Dams Design Faculty of Engineering and the Built Environment Department of Civil Engineering Embankment Dams Design (Cont’d) Faculty of Engineering and the Built Environment Department of Civil Engineering Embankment Dams Design (Cont’d) Design components: Permeability: rate at which soil will allow water to pass. Stability: ability to resist shear force. Compression and shrinking: sag under its own weight. Washing of fines: internal erosion of fines. Availability of construction materials: advantageous if within the vicinity area. Faculty of Engineering and the Built Environment Department of Civil Engineering Concrete Dams 1. Gravity dams 2. Arch dams Faculty of Engineering and the Built Environment Department of Civil Engineering  Concrete Dams (Cont’d) 3. Buttress dams Faculty of Engineering and the Built Environment Department of Civil Engineering Concrete Dams Design 3. Buttress Dams Faculty of Engineering and the Built Environment Department of Civil Engineering Concrete Dams 4. Masonry Dams Built of stone bedded in mortar Faculty of Engineering and the Built Environment Department of Civil Engineering Challenges Faced During Dam Construction Projects 1. Geological Uncertainties: Uncertainties in the geological conditions of the site can lead to unexpected problems, such as unstable foundations, water seepage, and landslides. 2. Environmental Concerns: Dam construction can have significant environmental impacts, including disruption of natural habitats, alteration of ecosystems, and effects on local wildlife. 3. Water Management: Managing water flows, levels, and quality during construction is crucial to prevent flooding, erosion, and water pollution. 4. Logistical Challenges: Dam construction often takes place in remote areas, making it difficult to transport materials, equipment, and personnel to the site. Faculty of Engineering and the Built Environment Department of Civil Engineering Challenges Faced During Dam Construction Projects 5. Safety Risks: Dam construction can be hazardous, with risks of accidents, injuries, and fatalities, particularly during excavation, blasting, and concrete placement. 6. Cost Overruns: Dam construction projects are often subject to cost overruns due to unforeseen site conditions, design changes, and delays. 7. Community Displacement: Dam construction can result in the displacement of local communities, requiring careful planning and management to minimize social impacts. 8. Seismic Activity: Dams must be designed and constructed to withstand seismic activity, which can be a significant challenge in seismically active regions. Faculty of Engineering and the Built Environment Department of Civil Engineering Challenges Faced During Dam Construction Projects (Cont’d) 9. Material Selection: Selecting the right materials for dam construction is critical, as they must be able to withstand the stresses and strains imposed by the dam's operation. 10. Regulatory Compliance: Dam construction projects must comply with a range of regulations, including environmental, safety, and water quality regulations. Faculty of Engineering and the Built Environment Department of Civil Engineering Technical Challenges 1. Foundation Design: Designing a stable foundation for the dam is critical, as it must be able to transfer the weight of the dam to the underlying rock or soil. 2. Concrete Placement: Placing concrete in a way that ensures its quality and durability is essential, particularly in areas with high temperatures or extreme weather conditions. 3. Waterproofing: Ensuring that the dam is waterproof is critical to prevent seepage and leakage, which can compromise the dam's stability and safety. 4. Drainage: Designing and constructing effective drainage systems is essential to prevent erosion and water accumulation around the dam. Faculty of Engineering and the Built Environment Department of Civil Engineering Technical Challenges (Cont’d) 5. Instrumentation and Monitoring: Installing instrumentation and monitoring systems to track the dam's performance and detect any potential problems is critical to ensuring its safety and reliability. Faculty of Engineering and the Built Environment Department of Civil Engineering Addressing Challenges To address these challenges, dam construction projects require: 1. Careful Planning: Thorough planning and feasibility studies to identify potential risks and challenges. 2. Experienced Team: An experienced team of engineers, contractors, and project managers to oversee the project. 3. Innovative Solutions: The use of innovative solutions and technologies, such as advanced materials and construction techniques. 4. Community Engagement: Engagement with local communities to minimize social impacts and ensure that their concerns are addressed. 5. Regulatory Compliance: Compliance with relevant regulations and standards to ensure that the dam is safe, reliable, and environmentally sustainable. Faculty of Engineering and the Built Environment Department of Civil Engineering Water Conservation Scarce commodity Rising population Climate change Seawater consumption? Grey water? Groundwater? Faculty of Engineering and the Built Environment Department of Civil Engineering Faculty of Engineering and the Built Environment Department of Civil Engineering