US Patent 7383896 Impact excavation system and method with particle separation

A system and method for excavating a subterranean formation, according to which a suspension of liquid and a plurality of impactors are introduced into at least one cavity formed in a body member and are discharging from the cavity so that the impactors remove a portion of the formation. The impactors are separated from at least a portion of the fluid, and are passed to a conduit so that the impactors accumulate in the conduit before being removed from the conduit.