Hi Mala, it looks like the separate surfaces problem is caused because your dome shape was an open surface instead of a closed solid when you did the boolean on it.

You should make the dome into a closed solid before doing the boolean. You can do that by selecting it and running the "Construct > Planar" command which will close off the bottom with a planar surface.

Additionally the cutting objects have a little gap in the middle area, they are also not solids. I closed those up by creating some lofts and joining those in.

- Michael