Repair of Underwater Piles

There is a large inventory of bridge, piers and off shore platforms worldwide that are supported on piles. The splash zone of these piles is subjected to dry wet cycles that results in rapid deterioration of these elements. Over the years, many commercially available systems have been developed to repair such elements. The majority of these systems include two half shells, typically made of fiber glass and customized to fit a specific pile size. The jackets are pre-manufactured and shipped to the jobsite in bulky crates. In the field, the jackets are placed around the pile and fastened together with steel bolts or straps. The annular space is then filled with grout and the shell is either removed or left in place.

There are three major shortcomings with these systems. First, these installations require advance scheduling and ordering of ‘custom fit’ jackets to match the existing pile dimensions. Secondly, they require significant time by divers to assist with the underwater installation. Lastly, the presence of vertical seam(s) along the height of the jacket introduces planes of weakness that prevent grout pressurization. While the latter leads to inferior structural performance, the first two attributes of these systems lead to significantly higher construction costs.

Similar to the methods described above for columns, a ‘seamless’ jacket can be made in the field around the existing pile (Figure 6). This product is marketed under the trade name PileMedic® by QuakeWrap, Inc. A single roll of super laminate can be used for a wide range of pile sizes and shapes, producing a cylindrical jacket around the pile. When field conditions permit, the jacket can be started above waterline (on the dry portions of the pile). Once a couple of turns are completed, the finished portion of the jacket can be gradually lowered into the water, while workers continue to construct the remaining portion of the jacket above waterline. Moisture insensitive epoxy putties are available that can be applied and are cured in water. These will greatly facilitate the construction of pile jackets in marine environments.

Once completed, the lower and upper ends of the annular space between jacket and pile are sealed, for example with a rubber bladder similar to a bicycle tube. Sealing of the lower part of the annular space is the primary task that may require assistance from divers. Then the annular space is filled, and if required, pressurized. The pressurization of the annular space will ensure that the grout or resin fills all the voids and crevices in the deteriorated pile. The pressurization also causes active lateral confinement of the pile, thereby increasing its axial load carrying capacity.

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