Sleeper and steel beam retaining wall

[william127]

A customer of mine is asking about having an rsj and sleeper retaining wall built, no problem there....

Except the steels will be going in under water so digging a hole and concreting them in isn't really an option.

He's currently looking to have them 'knocked in', 4ft into the ground (his spec, not mine. I'm currently working on a design that doesn't involve them going in so far, but they will still need knocking in a couple of feet). 

What would be the best type of machine for this job? Would a heavy post knocker on say a 3 ton digger work- it will need a bit of out reach and a tractorwont work on this site? An rsj has much less surface area than a large straining post but it's not something I've ever done.

Not sure there's even a job to be had here but he's a nice customer so I said I'd ask some opinions 👍

Cheers 

[Peasgood]

Don't see why it wouldn't work and don't see why you don't knock it in 4'. Only issue would be if you hit rock or roots.

[GarethM]

With the price of steel and sleepers, it'll probably be easier just to pour concrete pads and bolt them down and maybe use concrete panels ?.

 

What do you mean underwater, as in water table ?. Plus how much is going to be above ground as that's more the deciding factor.

[dumper]

Don’t knock vibrate much easier and far more accurate, 1.2 m might not be enough need that into good quality clay 1.5 to 1.8 might be better 

pouring concrete underwater not a good idea, have you worked out the pressure on the wall 

research your sleepers a lot of the oak available are turkey and will not last underwater 

[dumper]

Maybe try a duck anchor installed at the top into the bank will reduce the need for so much depth to the steels 

[doobin]

You’ll knock ‘em in enough to hold with a digger and post knocker. Did these a couple weeks back but I was surprised how much resistance I had on them into the clay. Went back and fetched the loader with the p180 but still on got them down a foot more than the 100kg knocker. Plenty enough to hold the bank back however, and like dumper says, you can always add a ground anchor to the top if you can’t knock them far enough down. 

Vibration may well work better but a vibration unit is a bit specialist, digger posts knockers are everywhere. Just go slow and make adjustments in good time. 

 

[cyberstag]

As a deer farmer we are used to knocking in tall posts, corral walling is using 12 foot timber posts. Friend of mine has done all his deer fencing using motorway crash barriers as strainers. they are 15 foot long and he has knocked them in 8-9 feet using his post driver, and that is into shillet, he only had a few where he had to cut a bit off the top. 

You should be able knock RSJs in ok with a decent post driver. Mine has a 14 foot mast and a 270 kilo hammer. As said before just make frequent adjustments to keep them plumb. 

[william127]

Thanks for the advice, I'll put some ideas to the customer and see what they say👍👍

[dan blocker]

It all depends on how many sleepers high and if it’s backfilled and with what? doobins example only looks to be about 2 sleepers high? And with the crescent shape will give extra support. Straight run, 4 ft into ground, 3 or 4 sleepers high, back filled with soil to top, will more than likely push over. Large secure/ tensioned  Duck/ ground anchors near the top of the steel would help.

[doobin]

14 hours ago, dan blocker said:

It all depends on how many sleepers high and if it’s backfilled and with what? doobins example only looks to be about 2 sleepers high? And with the crescent shape will give extra support. Straight run, 4 ft into ground, 3 or 4 sleepers high, back filled with soil to top, will more than likely push over. Large secure/ tensioned  Duck/ ground anchors near the top of the steel would help.

4 sleepers, just holding back the edge of the pond. I'd usually use a duck anchor if possible, simply as it negates any leverage from the length of the post. However, in your example, I'd say it's very unlikely to push over. To push over, a wall needs sideways loading, commonly from wet clay that's been dug and then backfilled. In most other substrates, almost all the force is downwards into the underlying strata. Three or four sleepers high is bugger all, and 4ft steel ipnto virgin ground will hold a lot. The RSJs I replaced in that pond job were leaning, but had been for years. When I pulled them up they were barely a foot into the clay!

 

At the end of the day, if Williams customer is specifying the wall, all he needs to do it buy/hire a post knocker for his digger, turn up and get paid!