I’m working on the assessment of 50 year old marina seawall. The seawall concrete panels, despite its age, are in fair condition with exception of some broken walers and cracking wall cap. The biggest problem is that the backfill is escaping through the panel to panel tang and groove connection gaps, which causes sidewalk and driveway to crack and break. Through the 50 years of wall existence some repair and maintenance work been done, including wall gap regrouting, but seems like this ongoing problem never ends. One builder suggested that, may be some kind backfill soil improvement needs to be done like a lime slurry injection or cement, or fly-ash stabilization along the seawall backfill. Did anybody have an experience with that? Is this a good idea to use soil stabilization technique to stop seepage?

I'd say your two main options are either modifying/stabilizing the soils to prevent their erosion or excavating and installing a proper wall drain behind the wall (that allows for seepage of water but meets filter criteria to prevent the soil erosion). Just be aware that the soil modification approach would probably allow water to build up behind the wall so you'd need to be sure that the wall can handle the related hydrostatic load.

The only way to prevent materials to escape is to use jet grouting columns located at proper locations. Normally the wall should be designed to withstand the water pressure.

You could place a fabriform filter mat behind the wall .It will permit water to pass but stops all fines. Grouting is also possible. You could fill behind the wall with clear crush and grout the material from the bottom up. You would need also grout tubes installed in the material to permit water passage. Just permeation grouting of the existing soil materials probably will not provide sufficient strength and will wash out, or it will form a water barrier which could cause excessive wall pressure.

Are the joint between panels vertical only or both vertical and horizontal? If vertical only, perhaps a drilling/grouting/soil boring contractor could drill vertically down immediately behind the joints and then fill the drill holes with a stiff grout or maybe granular bentonite. This should be cheaper than jet grouting.

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