Pipe Jacking: State-of-the-Art

Pipe jacking is a method of producing tunnels by placement of a precast reinforced final liner immediately behind the excavator by pushing the liner in sections with hydraulic jacks from a shaft. Pipe jacking is used in the United States for circular tunnels from 54 in. to 132 in. (1,370 mm to 3,353 mm) diam. One experiment jacked rectangular sections. Excavation is by full-face tunnel boring machine. Improvement of tunnel boring machines, alignment, and bentonite antifriction injection techniques have allowed pipe jacking to be used for runs between shafts as long as 2,100 ft (640 m) and in soils such as wet silts hitherto thought infeasible. As owner agencies and consultants recognize the economy and quality control advantages now attainable with pipe jacking, the technique should become more widespread for construction of tunnels.