GB1263464A - Improvements relating to the trenchless laying of underground pipes - Google Patents

Abstract

1,263,464. Mole plough. HUDSWELL YATES DEVELOPMENTS Ltd. 14 March, 1969 [15 March, 1968], No, 12783/68. Heading A1B. [Also in Division F2] A liquid composition is injected into a tunnel formed by a mole plough 10 so as to lubricate and form a bedding layer for a pipe length 24 which is forced into the tunnel behind the plough. The liquid may be an aqueous thixotropic gel of Bentonite in water, or may comprise soil or cement in water with or without Bentonite. In one method, Fig. 6, the pipe length is releasably connected at 60 to a frusto-conical tunnel expander 15 which is towed behind the mole plough, the liquid being pumped into the annular space between the pipe and the tunnel 33. A foam rubber plug 29 prevents liquid from entering the pipe. In a second method, Fig. 8, the mole plough makes its complete traverse after which the tunnel is filled with a predetermined amount of liquid 32. An apertured tunnel expander 83, releasably connected to the pipe length at 90 is then drawn through the tunnel by a winch cable 88. The tunnel expander may be in two parts, connected by a bayonet joint, the rear part being replaceable for use with different diameter pipes. The front part is connected to the mole by a universal link. A modified expander, Fig. 7 (not shown) has a toothed peripheral drum (70) powered for rotation and mounted behind a nozzle (71) for mixing the liquid into the tunnel walls. The liquid is pumped from a surface reservoir, mounted on a trolley or on the mole plough itself, a portion of the slurry being recycled into the reservoir through a pressure control valve.