Effect of DC stray current on rebar corrosion in cracked segment of shield tunnel

Abstract The calculation model of segment rebar corrosion is formulated to study the rebar corrosion induced by stray direct current in the cracked segment of a shield tunnel. The model includes the upper track bed structure because the concrete in this structure has electrical resistance and affects the stray current distribution. To verify the accuracy of the calculation model, a full-scale test of the shield segment is designed. The potential distribution and rebar corrosion law in the cracked segment under different input and output positions are separately investigated through calculations. The result shows that the rebar corrosion rate in the segment is related to the input mode and the distance of the rebar corrosion from the current input location. When the stray current output locations remain unchanged, the maximum current density in the rebar under bilateral leakage is approximately two to three times that under unilateral leakage. Increasing the stray current in the output sides reduces the maximum current density in the segment rebar. When the output edge contains multiple-segment cracks, the closer the current output position to the middle of the segment in the circumferential direction, the larger the current density.