Retaining Structure for lake front

[fargofarmer]

Friends,

I have a client who is planning for constructing a buttress wall or repairing an existing timber soldier pile wall with dead man anchors. This wall is located at a lake shore and retains a private property. The wall is approximately 11 feet tall and 25 years old. 50 Percent of wall is damaged and or collapsed. We gave couple of options include segmental block retaining wall with clean stone/gravel backfill and steel soldier pile wall to buttress the existing wall. The client wants to use less expensive method. Obviously, it is S.R. wall. The problem is the distance between the new retaining structure and existing structure should not be grater than 2 feet. If it is more than 2 feet he will encroach lake boundary. The client wants to use any other sea wall options. Another important information is we can hit rock at shallow depths.

Does anybody know about any other kinds of wall be considered there? I will be very thankful to you.

 

[fattdad]

I'd be looking for another type of client rather than another type of wall.

f-d

¡papá gordo ain’t no madre flaca!

 

[PEinc]

What is the depth of rock below the dredge line? What kind of soil is behind and in front of the wall? If there is sufficient depth below the dredge line to top of rock, steel sheet piling could be used. You would need tiedback sheeting if there is insufficient embedment for a cantilevered wall. If the wall needs to be tied back, maybe vinyl sheet piling could be used.

Any other type of wall that could be built would probably need a temporary cofferdam to hold back the lake during construction. This cofferdam could be either an earthen embankment or a sheet pile wall. However, why build a temporary cofferdam plus a permanent bulkhead when you can just build a permanent sheet pile builhead without a cofferdam?

http://www.PeirceEngineering.com

 

[fargofarmer]

I gave sheet piling option to the client. He thinks it is very expensive. I think rock depth is within 6 feet. The soil behind the bulkhead is predominantly sandy silt. What is your comment on constructing massive gravity wall with Redi Rock blocks or Stone Strong blocks.

 

[Boondog]

I have utilized helical anchors to stabilize failed timber walls similar to your situation. You can then face it with modular block. The anchors can be installed from the top and once the soil is stable, a block veneer can be installed from the bottom up. It only requires about 2 feet to work the facing in.

 

[PEinc]

A massive gravity wall could be built, such as Redi Rock. However, as stated above, "Any other type of wall that could be built would probably need a temporary cofferdam to hold back the lake during construction." I would not recommend using Boondog's suggestion. Sorry, Boondog.

Rock within 6' of what? Original ground or lake bottom? In either case, 6' is not enough embedment to cantilever sheet piling for a wall with an 11' exposed height. Therefore, you would need tiedback sheet piling or a gravity wall and the temporary cofferdam.

http://www.PeirceEngineering.com

 

[oldestguy]

Check into the cost of reject concrete blocks made at the nearest readi-mix plant. These are made from concrete still in the trucks and avoids wasting the stuff. They measure 2 x 2 x 4 to 6 feet, fitted with tongue and grooves top and ends.

Stacking them at a slight angle from vertical ought to avoid any tie backs, etc.

Cost is less than manufactured stone and the front sides look like "stone". Should be able to resist ice shoving and waves.

 

[Boondog]

Sorry you don't agree. I have used the helicals on similar structures of the same height with great results. Cost is less than sheet piles with tiebacks. With 11' feet of height and saturated foundation material, you will have a very hard time getting Redi Rock to work. Sorry, I've tried that too.

 

[PEinc]

Boondog, if the existing bulkhead is deteriorated("50 percent damaged"), I would not try to support it with one row of tieback anchors. There may not be good enough soldier pile embedment to prevent to piles from kicking out. Installing a lower row of tieback anchors would probably have to be done under water for an 11' high bulkhead. Also, the horizontal boards between the soldier piles probably need replacing. From the little I read here, the existing wall is done. Replace it entirely. As I suggested above, I would use a sheet pile wall, tied back with tie rods and deadmen. A gravity wall could be built, but I did not and would not recommend it. One other option (probably unacceptable to the property owner) is to place a sloped rip rap fill in front of the existing wall.

http://www.PeirceEngineering.com

 

[VAD]

fargofarmer

How expensive is this lakefront property or what is the sentimental value of this property to the owner. There are few options only and some of these have been discussed. Another option is to construct a micro-pile wall on the insid eof the existing wall. This will allow the piles to be embedded within the rock. This could be expensive but the owner has to weigh the consequences of costs etc. Permits to work on the lakeside of the property could be touchy given only 2 ft of space especially if excavation has to be undertaken etc. If working on the inside is acceptable then helical screw piles embedded to 6 ft depth is also a viable alternative by using verical and inclined anchors. The inclined anchors to be installed through the existing wall and tied to vertical helical piles. Low angle of installation of inclined helical piles would allow helical piles to act a deadman anchors. Use waler beams on the outside of deteriorating wall to tie tops of helical piles to deteriorating wall.

This is aretrofit situation and requires sitting on site abit and thinking about solutions. Desk studies not much value here. This is the real geotechnical engineering. Do not discredit existing structure as it still is doing some work and only needs some support for it to last another 25 years.