Relief well - allowable seepage velocity

[patsthilaire]

Hello forum members,
Can anyone help me or give me some tips on ways of estimating the maximum allowable seepage velocity of water (or maximum allowable flow) in relief wells placed on the downstream side of a dam ?

Any help or comments would be appreciated…
Regards

Patrick Saint-hilaire

 

[cjohnson]

Patrick,

Still interested in an opinion?

 

[patsthilaire]

Yes, I'm still interresed
Thank you

 

[cjohnson]

Patrick,

Well, better late than never. Sorry, I was out of the country for awhile, away from anything resembling a computer.

Seepage velocities can be calculated for earthen retaining structures, up to and including the maximum velocity. Above this maximum the risk of piping becomes signficant. Are we dealing with an earthen dam?

The factor we can adjust in the calculation pertinent here is gradient. Relief wells will induce a drawdown, and as such a gradient beneath the dam.

Is this the right direction for you?

 

[setthan]

halo...professional member...i have a question here....do anybody know what is the best way to reduce the force exert by the soil to the retaining wall?? i thinking to put some gravel particles there but it is not effcient to retain the soil...anybody got any brilliant, creative idea about it...do reply me as soon as possible....thanks..

 

[Focht3]

Patrick -

Check out Seepage, Drainage & Flow Nets by Harry R. Cedergren - published by Wiley-Interscience. If you "know" the pre-well flow and well discharges, then you have a good idea of how much is getting by -

 

[Daryoush]

Patrick,
Once a relief well is installed you should first perform sampling and testing to check if any internal erosion or piping is happening. This is done by taking samples of the outflow and running lab analysis for solid particles charge. Seepage velocities depend on the materials along the flow path. You should instead use the monitoring data to determine the hydraulic conditions of the project. Based on the data you would determine what safety precaution you need to take to prevent major damage or failure of the dam.

 

[Focht3]

[blue]setthan[/blue]:

Please start a new thread and post your question there. And I'll look for it -