Studies on Surrounding Soil during Construction using the Deep Pipe Jacking Method in the Deep Strata

In Japan when urban infrastructures need to be constructed, the difficulty of utilizing t he ground or shallow strata will necessarily lead to the more frequent use of the deep strata. The common construction methods are open-cut, pipe jacking, and shield methods.In recent years a new pipe jacking method has been established that can be adap ted to 20 m below the ground or more. Using the method, the drivage machine and the jacking pipe continue to move an underground until the completion of the driving. Therefore an over-cutting area (so-called tail-void) must be formed to lower the friction between the ground and the pipe. The tail-void is filled with lubrications. However, because the stress release of the ground continues to advance when the tail -void is formed, there are some challenges required to cope with the stability of the surroundin g ground. In order to utilize the pipe jacking method in the deeper strata layers, the theory, analysis and installation of tail -void have to be systemized, and such systematic data must be stored. Therefore, the conditions of tail-void in the deep pipe jacking method are discussed using numerical analyses.