Design and construction of prospect hole plugging during the construction of river crossing tunnel based on pipe jacking method

When pipe jacking operation is carried out in high-pressure water areas, high-flow geological conditions (e.g. prospect hole and crack) may bring difficulties to pipe jacking slurry circulation system, cutter check and replacement in the cabinet and so on. In this paper, the plugging of prospect holes and major cracks in Fuchunjiang pipe jacking engineering was taken as an example to introduce the prospect hole plugging technology used in the high-slope vertical curve pipe jacking operation under the complex geological conditions. The requirements for the establishment of driving slurry circulation in the normal operation of pipe jacking were analyzed. The parameters of normal sections were compared with those of the sections with prospect holes where driving slurry circulation cannot be conducted normally. Prospect holes and major cracks are plugged successfully by taking the following measures, such as sealing up outside the tunnel by using the shield tail grease, sealing up at the tunnel face, slurry performance index control and jacking parameter optimization, so as to provide safe and reliable operation environments for the check and replacement of pressurized inlet cutters during pipe jacking at high water pressure. This technology is advantageous with strong operability, low cost and good application effect. And it can be used as the reference for the solution of similar difficulties encountered during river crossing based on pipe jacking.