What is this double "be" meaning?

Given the sentence:

He didn’t have a clue what was going on, but he didn’t seem to be being expelled, and some of the feeling started coming back to his legs.

I guess that in ‘to be being expelled,’ ‘be’ is for making passive voice and ‘being’ is for the meaning of future, that is, ‘to be expelled’ would be being happened in near future. Is this the right guessing?

Solution 1:

to be being expelled is a present continuous passive, with the head verb cast into the infinitive so the phrase may serve as the ‘object’ of the verb seem:

(he) was being expelled ⇨ to be being expelled

So the middle clause of your sentence may be understood as

and it did not appear that he was being expelled

Solution 2:

You correctly identified be as passive, but being makes this a continuous, not future: in the process of being expelled.

It's a variation on I'm being [state], a common passive continuous form, differentiating this from one finalized: "I am being drenched" means "I'm under a downpour of water, which keeps drenching me." This is different from "I am drenched" which you'd say as you exit from rain into a shelter, when you're wet but no longer getting more wet.

Solution 3:

I don't see anything odd in the sentence. An accidental juxtaposition of words need not confuse the reader so long as the sentence can be correctly parsed.

{He didn’t have a clue what was going on, but}

{he didn’t seem to be} ... — {it did not appear like he was}

... {being expelled}, — {going to be thrown out}

{and some of the feeling started coming back to his legs.}

That should clarify, I believe.