  Topologically non-trivial vacuum structure in gravity models with Cartan
variables (vielbein and contortion) is considered. We study the possibility of
vacuum space-time tunneling in Einstein gravity assuming that the vielbein may
play a fundamental role in quantum gravitational phenomena. It has been shown
that in the case of RP3 space topology the tunneling between non-trivial
topological vacuums can be realized by means of Eguchi-Hanson gravitational
instanton. In Riemann-Cartan geometric approach to quantum gravity the vacuum
tunneling can be provided by means of contortion quantum fluctuations. We
define double self-duality condition for the contortion and give explicit
self-dual configurations which can contribute to vacuum tunneling amplitude.
