Lateral Squeeze/Mud Waves

[geomane]

Is lateral squeeze the same thing as a mud wave?

I can't find any references that relate the two terms. But based on my experience, I think they are.

I personally have not been involved on a project where mud waves were induced due to fill placement. If a mud wave did develop, what is typically done to correct the issue? Is the mud wave just continually pushed out and away from the fill area? Or can the material be undercut and removed (depending upon depth and gwt)?

I'm thinking the best way to prevent it from happening would be to place your fill in thin layers and run slope stability analysis to ensure your side slopes don't fail. Then it just turns into a staged construction scenario.

I have read through the FHWA manuals where the general rule of thumb is lateral squeeze should be considered if the fill load is equal to or greater than 3 times the undrained shear strength. And is also depends on the thickness of the compressible layer of interest and the width of the sloped portion of the embankment. Are there any other references that talk more about this failure mode?

I guess I would like to hear some of your experiences with mud waves.

 

[oldestguy]

You are correct.
"Or can the material be undercut and removed (depending upon depth and gwt)?

I'm thinking the best way to prevent it from happening would be to place your fill in thin layers and run slope stability analysis to ensure your side slopes don't fail. Then it just turns into a staged construction scenario."

This day and age they don't like creating a mud wave or similar that loses what before is a wetland. Makes it more difficult. It all depends ion the site a to what to do.

 

[miningman]

Well if it helps anyone , about 20 years ago I deliberately induced a mud wave during the reclamation of a tailings dam at mine closure. We dewatered / drained the tailings pond to the best of our ability. Next step was the placement of geotextile fabric. Then proceeded to dump waste rock onto the tailings and using heavy equipment then pushed and leveled the rock pad working towards the low spot where the pump was still located. From memory we placed about 2 meters of rock to give us the confidence that we would not lose our equipment. The action of working on the tailings resulted in significant additional quantities of water being squeezed out of the tailings and we had to run the pump 24/7 to keep up. A large " wave" of wet tailings developed as the work progressed.

Consultants told us we were crazy to attempt this, and I must admit there were times I wasn't sure about this effort. At times we stopped dumping to allow the pump to stay ahead of further fill placement. Absolutely no computer modelling but the job was sucessfully completed with the application of about 0.3 metres of organic matter and hydroseeding.

 

[BigH]

Read Krynine and Judd's (I believe) book - they describe the Michigan Rolling Surcharge method. I have used it to displace 13 m of tailings slimes in the past. Also, there was a paper written by Matich et al using dynamite to remould a lake silty clay in order to dump rockfill in making a causeway - had they not done this they would have had many foundation failures - as they remoulded and then displaced (i.e., formed mud waves), they were able to construct the causeway. (Northern Ontario 1960s). Also check out Matich Paper in the 1986 3rd Conference on construction and Mining in Difficult Soils.

 

[EireChch]

Are mud waves and rolling surcharge the same thing?

Never heard of the first term!

 

[oldestguy]

Mud wave is similar to water waves as to what it is. It's the soft soil moving due to the surcharge. Rolling surcharge is a procedure to apply extra load to soft stuff to make it squeeze out, similar to getting tooth paste out of the tube.

 

[fattdad]

I don't like either term. They are both general shear failure and evoke a safety factor of unity. When such matters occur slowly, then I just liken them to non vertical consolidation.

Oh, sure, folks use these terms. I just struggle with the first principals that inform such calculations.

f-d

ípapß gordo ainÆt no madre flaca!