The technology of exploration of frozen soil fences by means of acoustic raying is designated for monitoring of frozen soil fences before driving.

The main diagnostic characteristic of the integrity condition of frozen soil fences is the speed of longitudinal elastic waves in frozen soils. Instructional guidelines on monitoring the integrity of frozen soil fences by crosshole acoustic raying when constructing tunnels in difficult hydrogeological conditions, published in Leningrad in 1981, were approved by Glavtunnelstroy of the USSR.

The first works on monitoring of frozen soil fences were executed in 1974 at the Outwash section of the Kirovsk–Vyborg line of the Leningrad underground (O. Andreev, head of works). In 2001–2006 in St Petersburg, integrity monitoring of the frozen soil fences of 12 separate shafts was executed — 214bis (Karbysheva street), 507 (Olhovaya street), 440 (Shamuana street), 17/2 (Konyushenny pereulok) and others — which provided accident-free shaft sinking.