Yes. Article 2, Section 5 allows for expulsion upon the concurrence of 2/3 of the members. In the Senate that is either 66 or 67 depending on if the language is taken to mean 2/3 of all members(100) or 2/3 of the members voting(99 since presumably one doesnt vote on ones own expulsion resolution. No Senator has been expelled since the Civil War, so I would imagine that the finer points of the constitutional language would inevitably be litigated). Unfortunately, that 2/3 vote will not be a tough nut to crack. The Democrats plus the technically Independents that are really Democrats hold 46 seats. The GOP establishment only needs 20/21 votes to join with the Democrats to make the 2/3 threshold. Thats around 40% of Republican Senators. If McConnell wants Moore out, he almost certainly has the votes.Then the voters of Alabama should send him back in the second special election, and the third, and the fourth, ad infinitum.
I am perfectly ok with a 99-seat Senate.
I'd prefer a zero-seat Senate.
Should Moore be expelled that expulsion would unquestionably extend until the end of the current Congress in January of 2019. Even in 2019, it is not entirely clear that the Senate would be compelled to accept Moore should he be returned through election. The most relevant Article 2, Sec. 5 case precedent declined to reach a finding regarding the ability of a previously expelled member to stand for election to the seat from which that member was expelled.