(Shimada and Matsui, 1998). In order to protect the safety of workers during construction, as well as for environmental and cost reasons, slurry pipe jacking in long distance needs to be considered.
The jacking load is an important parameter, controlling the pipe wall thickness, the need for and location of intermediate jacking station, selection of jacking frame and lubrication requirements. The main component of the jacking load is due to frictional resistance (Pellet-Beaucour and Kastner, 2002). The needed thrust force to overcome on frictional force around the pipes is limited by pipe axial strength and this factor can control the length of jacking. Due to the costs for setting up and disposal, the construction of intermediate shafts represents a considerable cost factor and reduces the number of intermediate jacking stations is related to reduction of jacking force in tunnel construction. Also to enable construction tunnel in long distance where the use of additional pits is impossible as crossing under river and structures it is necessary to keep frictional force around the pipe string low. It is necessary to reduce the friction on the pipe conduit to increase effectiveness and lifetime of cutter tools because access to the face for replacing worn tools is particularly important for long distance tunneling (Adams, 2002). Usage of lubricant is an important factor to reduce frictional resistant around the pipe and increase distance of jacking also the pipe string can be moved at all times with the available jacking force. This paper discusses the method of prediction thrust during a slurry pipe jacking construction and proposes two equations for straight and curved jacking area.