Guided boring machine and method

Abstract

A guided boring machine includes a cutter head, a steering head and an internal casing with an auger therein for conveying material cut by the cutter head towards the rear end of the auger. The boring machine bores a tunnel from a launch pit to a target pit along a desired boring direction and simultaneously installing a selected one of a plurality of differently-sized product casings in the tunnel. When the internal casing is placed within a selected product casing with its internal casing longitudinal axis coincident with the longitudinal axis of the selected product casing, an annular space is formed with respect to the selected product casing. The guidance assembly includes a laser that is mounted behind the boring machine and oriented so as to direct its beam in a desired boring direction within the annular space. A target mount is mounted to the steering head inside surface. The target mount includes a roll correction slot which is parallel to the adjacent steering head inside surface. A target is mounted to the target mount and adapted to move with respect thereto. The target has a target point which is intersected by the laser beam when the cutter head is properly oriented with respect to the desired boring direction. A gradiometer is mounted to the target to indicate the roll orientation of the steering head, and a roll correction assembly is provided to roll the steering head, if desired, to adjust its roll orientation.