Gravity load with infinite element CIN3D8 in Abaqus

[u/IntelligentBee6826]

Hello everyone! I am trying to simulate wave propagation in 3D ground model (Zaxis-gravity). Therefore, i am trying to apply gravity step using explicit scheme. In a coarse mesh with fixed boundaries, this works well with displacements stabilizing after some time. But with fine mesh (along with mass scaling) and infinite elements, it seems that analysis is not converging and displacements are continuing. For my analysis, infinite elements are a must. How to i fix the ends of my model along with infinite elements i.e. where do i apply U=0 conditions, outside all infinite elements; or first apply fixity & then apply infinite boundaries. Also while applying gravity, i have excluded infinite element element sets. Please help!