Air bag support construction method for guaranteeing safety of shield tunnel underneath passing pipeline

The invention relates to an air bag support construction method for ensuring the safety of a shield tunnel underneath passing pipeline, which comprises the following steps: manufacturing an air bag and arranging the air bag at the bottom of the pipeline, and filling fine sand in a gap between two tunnels and between the air bag and a working surface; the air bag is inflated, so that the air bag expands to be tightly attached to the pipeline and the fine sand; when the distance between the shield tunneling machine and the pipeline is 6-8 times of the diameter of the shield tunnel, a strain change accumulated value epsilon t starts to be monitored, the air bags are inflated step by step through an air compressor, and the strain change accumulated value epsilon t is always controlled within 0.5 times of the maximum allowable tensile strain [delta epsilon t] of the bottom of the pipeline at the intersection position of the shield tunnel and the pipeline plane projection; if the condition that the strain change ac