What boundary conditions for column buried in ground?

[barrind]

I have to model the effects of an impact on a structure. The structure is basically a frame of vertical columns with horizontal bracing. The vertical columns are set in conrete block foundations approx 1m cubed, such that the top level of the concrete block is level with the ground surface. My question is how to define the boundary conditions for the concrete blocks, assuming I don't want to mess about modeling the ground and set up a load of contact interactions. Our civils guys were able to give me an equivalent spring stiffness of the ground which they use for calculating ground pressure from a simple side load on a single column. I know I can apply a spring to each of the concrete blocks but I am not sure whether it is right to apply this to all sides of the block, as there would only be resistance from the ground in the direction of movement. To my mind I need to apply a spring condition which only acts in one direction, and apply independant springs like this to all sides of the block such that only the springs being compressed act of the block. Has anyone on here had an experience of setting anything like this up?

 

[Yoman228]

You can use connector instead of the spring, then define a non-linear spring (so it can be be direction only).