I modelled soil structure interaction using solid 45 for soil and steel plate and contact  174 , target 170 , sweep mesh, fixed support for sides and bottom. And two steel rebars in soil by Link 180 I did mesh the soil plate and rebars . modelled contact pair. Analysis static. use small static displacement in solution controls, turn automatic stepping on, gave max, min, and time steps, line search on also, dof predictor for all substep, number of alteration 100 but I did get this error hope you help me solve this problem:

 *** ERROR ***                           CP =     117.766   TIME= 13:554
 The value of UZ at node 1239 is 17771738.3.  It is greater than the
 current limit of 1000000 (which can be reset on the NCNV command).
 This generally indicates rigid body motion as a result of an
 unconstrained model.  Verify that your model is properly constrained.

 *** ERROR ***                           CP =     118.375   TIME= 13:559
 If one or more parts of the model are held together only by contact
 verify that the contact surfaces are closed.  You can check contact
 status in the SOLUTION module for the converged solutions using

 *** ERROR ***                           CP =     118.406   TIME= 13:559
 Rigid body motion can also occur when net section yielding has
 occurred resulting in large displacements for small increments of load
 or when buckling has occurred.  You can plot the time history curve
 for node 1239 in the UZ direction to check for stiffness (slope of the
 curve) approaching zero.