The behavior of synchronous grouting in a quasi-rectangular shield tunnel based on a large visualized model test

•A large model test on the behavior of synchronous grouting in quasi-rectangular shield tunnel.•A periodic change in short-term and a staged change in long-term of grouting pressure.•The visualized model test can record the flow path of grout and final grout shape.•The grouting pressure fluctuates around the segment in the toroidal direction.•The experimental results can provide a new grouting pressure mode for the design of shield tunnel linings.