Suggestions for taking out fortifications

[junk2drive]

I am having a hard time advancing against bunkers, sandbag MGs and spider holes.
I have had some success with tanks and flame tanks.
Sometimes infantry close assaults give hit messages of "track hit" etc.
Artillery hits, air strikes, helo rockets, all seem to do little or nothing.
Other than avoiding and bypassing these things, is there a trick to destroying them?