Vertical and Horizontal Arches
Ground freezing can be utilized to assure stability of sequentially excavated (SEM) or hand mined tunnels. The freeze pipes may be installed vertically or near vertically from the surface, or they may be installed horizontally from access shafts to create a frozen envelope parallel to the tunnel alignment. With either freeze pipe orientation, a full face freeze may be an advantageous option, depending on the excavation method, so the excavation sees homogeneous conditions.
Cross Passages and Connector Tunnels
Ground freezing can be utilized to facilitate connections between structures such as a cross passage between twin tunnels or a mined connection between deep structures. The frozen ground will conform to adjoining subsurface installations or obstructions, if necessary, to provide a composite cut-off structure.