A rock mechanics question

[jainslie]

I have a simple rock mechanics question.

Here's the situation. I have a project what is going to place a large load bearing directly on limestone bedrock. The problem is that 10 feet into the bedrock there is a void. I need the equation to determine if the rock layer is sufficient to support the load.

As a bonus if there is a way to determine weither or not a load applied to limestone will compress a shale layer and thus cause failure I would like to know.

Thanks

 

[phillyfrank]

This is NOT a simple question. It is a highly three-dimensional problem. You will be best modeling the situation using some finite element or discrete element code -- not for amateurs. Simple beam theory does not account for the geometrics and fracturing.

 

[Backfill]

Jainslie:
Phillyfrank is right, it's not a simple question. Here's another slant on it:

Do you need to maintain the void integrity? If not, can it be pumped full of concrete, grout, etc.? At only 10 ft to the back of the void, can you open the ground up and assess the void?

Regarding the shale question, you need to let us know more about the load and the geometries. Also, failure can come in degrees, with some levels being acceptable.

Gluck Auf

 

[phillyfrank]

Backfill has many good points. If the load bearing is a sensitive or valuable structure, backfill the void, or excavate it out. Drill hole cameras can be placed to survey the void and its condition. Good luck, indeed.