yes, you can use ABAQUS for simulating the piled raft foundation with depending on the load use fine, medium or coarse mesh for the analysis..I suggest you to collect the research paper related to your work mainly numerical analysis based paper using abaqus..also, suggest you to read abaqus manual to understand the simulation process..then, simulate your problem after studying the research paper and abaqus manual..ok all the best in your research..

For meshing you need to do mesh optimization before you start the simulation. Just change the mesh size and get the results until you get a similar results. then, that 's your optimized mesh size

Yes, what you want?

It's a good program to simulate the concrete, soil, and athor materials.