Retaining Wall running perpendicular to shoreline and into water 1

[TurtleDog]

Hey yall,

I've taken a job building a lakefront cabin up in Northern Saskatchewan. I've attached a few pictures.

The client also wants a 100' retaining wall built along the length of their property right to the waters edge.

It is a very unique property though. The water level in the lake began to rise drastically about 5 years ago, so the previous owner was forced to completely remove their old cabin 3 years ago and build the whole lot up approximately 4 feet. The property borders a public walkway, as can be seen in attached picture, and they were not allowed to build up any of that land, so the bottom of the sloped rocks is essentially the property line.

The new owners are wanting to make that approx 8' of sloped rock usable land again, so they are wanting a retaining wall built the entire length of their property line. Which is fine for the first half of the wall, it's the last 20 feet that has the potential of being completely submerged from year to year that has me very concerned, We would be using large 2'×4' concrete blocks for the wall. Will that be heavy enough to remain in place, even if they end up submerged and frozen over winter? I've never dealt with a project quite like this, just hoping for some advice/suggestions on how to possibly deal with drainage/reinforcement.

The water level has also receded severely this summer already so there is no issue with placing the wall up this fall, it's just the potential water rise again in the future that has me worried.

Sorry about the long question, thanks a lot in advance!

 

[SlideRuleEra]

What you are describing is essentially a revetment. Here are references that should be helpful:

"Design Manual For Articulating Concrete Block Revetment Systems" by National Concrete Masonry Association

"Use of Articulating Concrete Block Revetment Systems for Stream Restoration and Stabilization Projects" by U.S. Department of Agriculture

"Design of Coastal Revetments, Seawalls & Bulkheads" by U.S. Army Corps of Engineers

 

[TurtleDog]

Thanks for the response,
So what's there currently is essentially a revetment wall. What the client is looking to do is rather than have an 8 foot wide unusable slope. They want a retaining wall built right at the and of the current slope. Which then allows them to be able to use the now level ground. Thanks!

 

[SlideRuleEra]

We would be using large 2'×4' concrete blocks for the wall.

If the blocks will be stacked, then the design becomes a sentimental gravity retaining wall. Often, blocks for this use are constructed to lock together to make the wall act as a single structure when loaded. See "Design Manual For Sentimental Retaining Wall" by NCMA.

 

[BridgeSmith]

...sentimental...

Autocorrect?

 

[Jack Walter]

Hey Turtle Dog,

Would the client go for an anchored sheet pile wall? that is what we would do for this scenario down in Florida.

You drive something like a Vanguard HD corrugated Viynle panel down with embedment equal to 40% to 50% of the exposed face of the wall. The top of the wall would have tiebacks every 10 feet or so and a concrete cap would be sized to resist the moment and shear between the tiebacks. For tiebacks we would use concrete Deadman approximately 3' wide x 3' deep 3' under the ground. For drainage you install well points 6" above the high water mark, for this case you would want to go 6" above the typical water elevation.

I imagine it would be cheaper than concrete blocks although I could be wrong. They also make steel sheet or concrete sheet piles.

If they would go for that it may be a better solution. The U.S. Army Corps sheet pile manual is a good place to start.

 

[BridgeSmith]

Sheet pile could work, depending on the embedment material. It pretty much has to be medium dense to loose sand, without any big rocks. If you have material the sheet piles can be driven in to a depth equal to the exposed height, that's usually sufficient to do it without tie-backs.

Gabion basket walls can also be a good solution for walls that get inundated with water.

 

[SlideRuleEra]

Thanks, BridgeSmith... "segmental"... that's what I get by posting while on vacation.

 

[BridgeSmith]

I've seen much worse results of autocorrect 'fixes'.