Repair | Waterstop technology
Joint leakage in concrete gravity dams and locks is often seen as an unavoidable challenge. Grant Waring, President of Emagineered Solutions, gives an insight into how expectations can be redefined
Right: Monolith joint leakage poses hazard to electrical equipment and personnel
Below: John Day Dam Bottom: Drilling receptor hole
TO ACCOMMODATE MOVEMENT AND alleviate stress in concrete gravity dams, transverse expansion joints (monolith joints) are typically located every 20-30m along the axis of the dam. During construction, a barrier spanning the joint is cast into the concrete monoliths on either side: the waterstop. These joints experience frequent and recurring movements due to seasonal temperature changes, fluctuations in reservoir elevations, foundation settlements, and other factors. The cyclic movements of the joint cause the original waterstop to fatigue and eventually fail. Failed monolith joint waterstops allow water to enter
the internal rooms and galleries of the dam, and even to pass through to the downstream face. Such leakage poses numerous issues, including: Slip hazards Electrical hazards Downstream face icing and ice accumulation Excessive pumping demand Corrosion Deterioration of concrete along the joint and at joint face Public perception of compromised dam integrity Lost value of stored water through uncontrolled leakage
These issues can pose significant safety, operational, and public relations risks.
The cure Emagineered Solutions(ESI) has developed a
waterstop technology called CYLutions to help solve the unique challenge of restoring the watertight seal along monolith joints. This CYLutions process is a targeted repair from the top of dam and does not typically require marine vessels or diving. It can be performed at any time of year and installed in active leaks, under full head. Installation of the remedial waterstop requires development of a vertical receptor hole along the full depth of the joint. This is usually accomplished by drilling a borehole, precisely centred and aligned on the joint from the top deck down to the bedrock. In some cases, an existing vertical joint drain can be re-purposed to serve as the host for the new waterstop system. The CYLutions product is a hydrophilic
polyurethane, supplied in solid rubber-like cylindrical segments, slightly smaller than the receptor hole diameter. Segment lengths can be customised to suit project constraints but are typically 1m in length. The pre-formed segments are manufactured under controlled conditions at our US facility and shipped to site, ready for installation. Installation is performed by simply placing cylinders in the borehole by hand, one at a time, until the borehole is filled above the high water level of the reservoir. Segments swell upon immersion in water to
34 | August 2024 |
www.waterpowermagazine.com
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