Innovative seismic stabilization: 6 cutting-edge techniques for dam piers

Recent seismic hazard assessments reveal that many older dam-discharge facilities, such as spillways and outlet works constructed in the early 1900s in areas prone to earthquakes, may face substantial seismic forces.

These structures were first designed with no, or minimal, consideration for earthquake impact and are often inadequately reinforced. To mitigate this, analysis and stabilization techniques are being explored on several existing dam upgrades.   

Dam spillways and intake piers are often a dam's weakest points and differ widely in size, reinforcement, supported boundaries, and stress. It's crucial to factor in the key strength parameters when assessing them.    

For instance, the friction angle at a pier's base can vary significantly due to joint preparation throughout construction.   

To secure these critical points, innovative analysis and design solutions are necessary to ensure that dam parts function and the dam itself remains stable.    

 

Here are six cutting-edge techniques for innovative seismic stabilization: 

1. Post-tensioned anchors: Strand or solid bar post-tensioned anchorscan compress the dam pier interface and control tensile stresses caused by lateral loading. This technique can stabilize the pier base or lift joints under seismic loads. 
2. Lateral support systems: A concrete deck or struts that connect the dam piers to the valley sides or other structures can make the piers stronger and more stable during seismic events. These systems must be tied to the abutments or adjacent gravity dam structures to minimize pier deformations. 
3. Lateral strut bracing: To stabilize piers with large displacements at the top, lateral strut bracing (independent from the existing bridge structure) can be combined with post-tensioned anchors. Steel strut systems are cost-effective and light. 
4. Using existing hoist deck with retrofit strut bracing: An existing deck capable of bearing traffic on the dam and holding flow control gear can be used. This method's feasibility hinges on various elements, such as the condition and strength of the pre-existing deck. 
5. New composite deck as strut bracing: A new deck that supports flow control equipment can also stabilize dam piers, especially if new gates and hoists are needed. A composite system of reinforced concrete slab and steel girders can provide bracing and crack control for the piers. 
6. New parapet wall with new or existing deck as strut bracing: When a parapet wall is needed on the intake deck, it can double as a strut brace that's part of the deck to enhance pier support. This means the parapet wall serves as a concrete beam, providing tension and compression support between piers. 

 

Any effective stabilization method must adapt to the unique site-specific circumstances and construction-related issues distinct to each location.   

Today, many dam structures are under-reinforced due to low or no seismic loading considerations in their original designs. Innovative techniques are required to stabilize these structures to ensure operability of dam flow control components and provide overall stability.   

We understand the importance of addressing seismic and post-seismic pier deformations and we partner with stakeholders to design bespoke, custom solutions to mitigate this risk. 

Connect with our hydropower and dam experts to find out how to develop innovative approaches and cost-effective solutions.