Construction method for large-section rectangular jacking pipe underneath passing through river shoal to meet obstacles and escape danger

The invention discloses a large-section rectangular jacking pipe underneath crossing river shoal obstacle encountering and danger avoiding construction method which comprises the following steps: S1, when the rectangular jacking pipe underneath crossing river shoal encounters the conditions that the current of a cutterhead and a screw machine stays at a high level and the torque of the cutterhead and the screw machine is sharply increased, reasons should be checked in time by means of forward and reverse rotation of the cutterhead, forward and reverse rotation of screw machine blades and the like; s2, the water flow of the river shoal is small, treatment can be conducted in a local excavation mode, and river water is guided before local excavation; s3, excavating and cleaning soil, filled stones and the like in the soil covering range of the riverbed in front of the pipe jacking machine by adopting an excavator, wherein the excavating depth is the soil covering depth from the top of the pipe jacking machine t