Bentley Team,
I am currently designing a 9-story residential building with a mat foundation. We are trying to determine at what depth is the mat foundation required to be based on sliding and overturning moments. I do not know where to start looking to verify that both overturning and sliding is acceptable and within a factor of safety. Any guidance on where to start looking? We have no area experiencing negative soil bearing - is that the check for overturning?
How can we account for the mat foundation being X ft below grade?
Attached is the result of the mat foundation. I only reviewed Service LCs as they are the only ones showing maps. Is there anywhere else i should be reviewing these maps/soil reactions?
As always, thank you for your assistance.
PDF
If there is no area in tension, then it's not lifting up or overturning. There is no factor of safety in the per se, it's just in static equilibrium. If the mat is buried, then you probably want to apply additional dead loads on top of it.
For sliding, one might apply a lateral spring constant, or some line springs along the edges (or both). This is not exactly like friction, however. Sliding deflections will be linear, based on the horizontal force. So again, you can check the deflections, or the reactions, but this is not exactly the same as checking sliding stability with a factor of safety.