×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

How can I seal off underflow in a weir?

How can I seal off underflow in a weir?

How can I seal off underflow in a weir?

(OP)
I am trying to come up with a practical method of sealing off the underflow under a proposed new weir in a very inaccessible gorge. I dont know the depth of the rock and the river bed is filled with large boulders. Do I drill & grout or what?

RE: How can I seal off underflow in a weir?

What material are you talking about grouting?  The alluvium?  If the critical layers don't contain too much in the way of fines or fine sand, there is a possibility of permeation grouting.  Probably can't drive sheet pile if many boulders are present.  How about excavating a c/o trench and backfilling with lower permeability material?

If it's the bedrock in need of grouting, conventional cement grout may be all you need.

Might get SOME benefit from an upstream blanket, but it's not a very reliable solution - depends on where the seepage gets into the critical material.

Can't say much more without knowing specifics.  If you don't know the specifics either, better get some exploration.

Regards,
DRG

RE: How can I seal off underflow in a weir?

Rock dam grouting.
Not easy, need to drill then grout .On a similar project a  80 ft deep rockfall filling a gorge we used a 7" drill bit 3 lines of grout holes at 2- 3 ft centers. Downstream line was first filled with 3 " rock to fill voids in large rocks, middle line was filled with 1" rock, again to fill large voids and upstream line of holes then filled with pea gravel. The intention was that the gravel and pea gravel would migrate downstream and gradually fill the voids in the 3" rock that was first dropped into the downstream line of holes.This would reduce the void sizes to as small as possible and enable grouting ,if you have some water flow.
You will need to keep topping up the various holes
as they settle.
 If if you cannot slow the flow enough to grout, you need to stop the flow as much as possible by building a higher temp dam downstream to reduce the pressure differential in the first then you can grout.
 Environmental considerations if fish are present should also be considered.The ph downstream should also be monitored. Grouting if ph levels are critical can be very slow to reduce the volume/hr of grout leaking into the flow to minimise ph level changes.

 Alternatively if you have one or a number of definite entry channels you can use fabriform concrete
bags or mat as a plug, or just one of varois types of liners, a definite answer depends on the actual situation.

Intrusion Prepakt /marineconcrete.com

RE: How can I seal off underflow in a weir?

For a gravity-arch dam constructed in the late 50's early 60's on the Skagit River in Washington State, a freeze curtain was used.  Worked very well during construction.  Dam is still there too.  That's a very good sign...

Mike McCann
McCann Engineering

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources