METHOD FOR HYDRAULIC GROUND EXCAVATION AND TRANSPORTATION Russian patent published in 2006 - IPC E02F3/88 

FIELD: dredgers, soil-shifting machines, particularly adapted for underground ground excavation.

SUBSTANCE: method for hydraulic ground excavation and transportation with submersed jet generated by hydraulic monitor involves eroding ground with submersed jet; ejecting the resultant pulp in series by central and annular ejecting nozzles. Working water of the second stage is injected directly downstream of receiving chamber at length, which prevents contact between expanding jet exiting central injecting nozzle and receiving chamber walls. Outlet receiving chamber end is made as removable collar. Rate of water flow through annular nozzle is 15-20% of that of water flow through central injecting nozzle.

EFFECT: reduced hydraulic loses in mixing chamber, decreased abrasive wear and increased net pressure head in two-stage ejector.