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Antonio Carlos Ribeiro - thanks for the answer, but as I wrote in the question, I tried to avoid using joins, since I have a complex query, but it does not use joins (and there is a reason for this).
I managed to do it myself :) In fact, it was quite simple: all I had to do was use DB:raw() , which allows us to inject the unformatted part of the request:
->from(\DB:raw('table_1 as t1, table_1 as t2'))
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