River Surfing Wave - Underwater Anchors

[NeilSurf]

Hello Everyone,

I am building am adjustable river surfing wave and am anchoring the wave shaping structure to a bedrock river bottom. The river I am in turns off for about 12 hours each day. Currently, the plan is to use Hilti HIT RE-500 SD anchors with 12" embedment provided the anchors pass a few onsite tension pull out tests. The river is just above freezing and the anchors will be fully submerged during installation. The problem is the HIT RE-500 SD have a 72 hour cure time and the river will be cycling on and off a few times. The current plan is to build temporary protection around each anchor to allow it to cure with minimal interference.

Do you know of any good underwater anchoring systems for 0C/32F water that cure in less then 12 hours?

Link to Wave Structure Image
The anchors are for the steel plate platform

Thank you,

Neil Egsgard
Surf Anywhere Project
www.SurfAnywhere.ca

 

[KootK]

I turned down an identical assignment earlier this year. I did't feel comfortable with the hydraulics, doing the anchoring without geotechnical guidance, and the real potential for people to get hurt. Hopefully you're more qualified for this than I am. I'll be keen to hear what comes of this.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[CELinOttawa]

I'll echo Kootk's sentiments, and add that Hilti's tech support is fantastic. Call them.

 

[dhengr]

NeilSurf :
Why not something like Simpson’s “ Titen HD’s”. There’s no need for a structural epoxy in the hole for strength. Check with them about corrosion resistance and alternating dry and wet conditions. Ask them what would happen if you just greased the holes with a quick curing epoxy at a hole sealing means. Then, just set the base pl. or anchor pl. in a good bed of quick curing epoxy to form a seal and a good bond/bearing surface. You might also set your wave shaping structural system into some shear keys cut into the rock river bed. Most of the loading would be taken by these shear keys, in bearing. Also, consider some soft o-ring/washers btwn. the stl. base pls. and the rock, just to keep rushing water out of this space. How does hydraulic cement work as a base pl. grout in these situations?

 

[DBronson]

NeilSurf:

You might want to investigate Williams Rock Bolts. They're designed to do what you're planning and they don't use epoxy.

Link

Regards,

DB

 

[KootK]

You might consider soliciting help from a local bridge engineer Neil. They would likely have a better handle on the hydraulics and the requirements of the local jurisdiction regarding stuff installed within waterways.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[tbuelna]

Your Hilti anchor bolt adhesive will set within 2 hrs. given the conditions you describe. While it won't fully cure for at least 12 hours at 40deg temperatures, as long as it sets before it gets submerged in water it should be OK.

But you also need to pay attention to the knock-down factors Hilti describes for the cured adhesive mechanical properties when applied to a wet surface. Due to such uncertainties in the mechanical strength of the anchor bolt adhesive, it would be a good idea to use a conservative factor of safety when calculating the number of anchor bolts required to restrain your wave generating device.

Good luck with your project. I grew up in coastal So. California and have surfed since I was 10 years old. Being a die-hard surfer this sounds like a neat idea to me, except for the fact that the water temperature is just above freezing!

 

[NeilSurf]

Thanks for the feedback everyone and the good will! I contacted Williams Form and discussions with them are leaning me towards a mechanical anchor. The hole size is much larger but it can be loaded immediately. The hole for the epoxy anchors is 3/4" in diameter and for a mechanical anchor of similar strength the hole size is 1 3/4". I have the regulatory requirements sorted out, I am reviewing the key areas of the project to see what can be improved. The anchor strengths take into account strength reductions due to submersion during installation, sustained load and anchor spacing. The required anchor strengths have been multiplied by 5 to give a good safety margin. Before doing the full installation we are installing some test anchors and ripping them out with a hydraulic puller to check the tension strength. I will let you know how this turns out.

Thanks again for the help and feel free to share any other suggestions.

Regards,
Neil

 

[cvg]

Hilti HIT RE 500 SD supposedly works down to 165 feet deep. I planned to use that on a project but it was 240 feet below water surface and for various reasons we switched to Williams S7 threaded studs instead.