The type of rock plays a critical role in the construction and engineering design of pumped hydro storage (PHS) facilities, particularly when underground caverns or powerhouses are involved. Key aspects influenced by rock type include structural stability, safety, and feasibility of excavation.
Role of Rock Type in Pumped Hydro Storage Construction
- Structural Integrity and Stability: The host rock must have sufficient strength and stability to safely support underground powerhouses, caverns, and tunnels used to house reversible pump-turbines and associated infrastructure. The intact rock’s compressive strength relative to the maximum stress on cavern contours indicates the likelihood of rock mass failure and guides design decisions. For example, values of the ratio of intact rock compressive strength to maximum stress indicate safety margins—medium values around 5 are desirable, while very low values around 2 indicate a need for intensive monitoring to prevent collapse.
- Excavation and Engineering Feasibility: Different rock formations, such as bedded sedimentary, metamorphic, or clastic rocks, present varied challenges for excavation and cavern construction. The rock mass failure modes depend heavily on whether the host rock is bedded or non-bedded and the type of rock present. Hard, competent rock formations generally allow for more stable underground structures but might require more sophisticated excavation techniques.
- Design of Caverns, Pillars, and Chambers: The dimensions of rock pillars between caverns, the height of transformer caverns, surge chambers, and overall plant capacity are linked to rock type and its mechanical properties. Rock formations with higher compressive strength can support larger caverns and heavier infrastructure.
- Reservoir Construction and Lining: Although the reservoirs themselves are typically made with concrete or asphaltic concrete linings, the geological foundation and surrounding rock affect reservoir stability and seepage control, influencing construction methods and materials used.
- Example Case – Drakensberg Pumped Storage Scheme: This project includes an underground power station housing reversible pump-turbines within a rock mass that must be engineered carefully to ensure safe and durable construction. Detailed rock engineering assessments were fundamental to the project’s design efforts.
- Utilization of Former Mine Sites: Sites such as abandoned coal mines can offer favorable conditions due to existing elevation differences and rock formations suitable for converting into pumped storage facilities. However, geological assessments remain essential to understand the rock mechanics and plan construction accordingly.
Summary
| Aspect | Influence of Rock Type |
|---|---|
| Structural stability | Determines safety and design margins for underground caverns |
| Excavation feasibility | Controls difficulty and methods of rock excavation |
| Rock mass failure modes | Varies by rock type, affects monitoring and supports design |
| Cavern and pillar dimensions | Rock strength governs size and spacing of structural elements |
| Reservoir foundation stability | Affects seepage control and reservoir lining requirements |
In conclusion, the rock type is fundamental in pumped hydro storage facility construction, particularly for underground components, as it impacts structural integrity, excavation methods, and overall engineering design to ensure long-term operational safety and efficiency.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-role-does-the-type-of-rock-play-in-the-construction-of-pumped-hydro-storage-facilities/
