modelling burrowing in slope stability

[ac4u2nv]

Dear all
Im modelling a slope in Geo5 slope stability - any ideas how i could model animal burrows and their affect on the stability of the slope?

Thanks
A

 

[geomane]

Animal burrows are usually more of a seepage and internal erosion type of issue

 

[oldestguy]

That situation is similar to the question of test borings. Do they affect strength? Maybe, but we usually don't see any problem related to test borings.

 

[Mad Mike]

I'm glad you brought this up- in a few days time I'm going out to inspect an earth dam that has failed; it was bone dry for ten years of drought and then blew out in a localized section when the first floods came. It's in the thick of our African bush and I suspect strongly that burrowing animals played a role...

How to quantify when these things are a problem is a mystery to me. How to prevent animals burrowing is also a mystery to me (synthetic liners may be an option, but I'd worry about durability).

I don't suppose you could ever model them analytically, but any field tips on how to visually appraise them would be most welcome.

All the best,
Mike

 

[EireChch]

You could (try) model it in Plaxis or some FEM and assign very low strength and stiffness parameters to the burrow.

I would have to be in some 3D format as if you model a burrow in 2D it will fail through the burrow obviously which isnt really correct as the burrow isn't continuous in 3D.

Its not something that I imagine many people have done or tried.

 

[fattdad]

5-ft tension crack, filled with water everywhere on the slope face?

f-d

ípapß gordo ainÆt no madre flaca!

 

[ac4u2nv]

Geomane/oldest guy so are you saying the burrow themselves arent an issue i.e. they wont destablise a slope or cause surface subsidence - however they lead to issues due to pathways for seepage etc..?

thank you

 

[oldestguy]

In that case likely since the burrow will feed water well into the dam without any head loss. Even one such burrow could be sufficient. I'd check what those animals do for burrows elsewhere to find their habits.

 

[fattdad]

animal burrows shorten the flow path assumed by the flow net. That can be a problem, i.e., there are case studies related to critical gradients, piping and such risks.

You asked about slope stability, which (to me) is another matter - not that both are not critical!

f-d

ípapß gordo ainÆt no madre flaca!

 

[geomane]

I’m not saying they won’t cause shallow slope failures; I mean if they turned your slope into Swiss cheese, then I would be concerned.

The seepage and internal erosion type failure modes come into effect if your slope is loaded with water on one side. A levee for instance. Internal erosion requires water and hydraulic gradient to initiate and progress. If your slope isn’t holding back water, then internal erosion shouldn’t be an issue.

I’m involved with miles and miles of annual levee inspections. We see animal burrows all the time but have never seen a slope failure occur due to them.

Can you post some pics?

Sounds like you need some kind of critter control and to fill the voids from the animal burrows.