Study on the pipe friction resistance in long-distance rock pipe jacking engineering

Previous studies on pipe friction resistance are mainly concentrated in the soil layer, whereas the study on that in the rock stratum is limited. To estimate the pipe friction resistance in the rock stratum, the calculation models of pipe friction resistance and their application conditions were compared first. Then the friction resistance calculation model for pipe jacking in the rock stratum was established and simplified. Lastly, the measured (FM) and the computed (FN) pipe friction resistance was compared to validate the simplified friction resistance calculation model. The following conclusions can be drawn: (1) The existing calculation methods of pipe friction resistance can be well verified in the soil layer but cannot be applied in the rock stratum. (2) Sediment, pipe–rock friction coefficient and mud buoyancy are the main factors affecting the pipe friction resistance in long-distance rock pipe jacking engineering. (3) The simplified calculation model established by Deng et al. can estimate the pipe friction resistance in different rock strata at different jacking stages with satisfactory outcomes. Further research on the pipe-rock friction coefficient in different rock strata with different pipe–rock contact conditions merits further investigation to better predict the pipe friction resistance in the rock stratum. The research results have certain practicability and can provide a reference for similar projects