Lubrication property requirements for injection into over-cutting area using extra-large-diameter slurry pipe jacking

Lubrication can effectively reduce the needed thrust if a discrete layer of lubricant is maintained between a pipe and the excavated soil. A lower frictional force allows greater jacking lengths to be achieved. The reduction of frictional stress around the pipe strongly affects the efficiency of lubrication injection. The lubricant must be designed to form a layer in the surrounding soil, be pressurized to overcome ground water pressure and stabilize the over-cutting area. The lubricant should also fill the over-break void completely to minimize surface settlement. However, for a commercial lubricant to be effective, it has been suggested that ingredients such as sodium and potassium be eliminated. As a result, in order that a lubricant does not lose its function as a support against the overburden pressure of an over-cutting area and to enable a reduction in thrust, a higher quality lubricant which can overcome these problems must be developed as soon as possible. In this paper, in order to examine the characteristics and behavior of a material developed as a lubricant for extra-large-diameter slurry pipe jacking systems, a fundamental investigation is performed and the various results are discussed.