Solid-fluid-gas coupling prediction of harmful gas eruption in shield tunneling

•Solid-fluid-gas three-phase coupling in FLAC3D was implemented by the Fish language.•A good prediction of harmful gas eruption was done by the numerical modeling.•Some safety standards for the tunneling in the harmful gas strata were put forward.•An automatic monitoring system was designed for the shield tunneling construction.

In some cities in the south of China, a stratum of explosive gas was often be encountered in shield tunneling, as well as in other countries. However there is no function of explosion-proof function in the shield machine, and it is likely to cause a large number of harmful gases gushing out instantaneously. The harmful gas concentration can exceed the safety alarm value and even lead to explosion. Based on the above issues, solid-fluid-gas three-phase coupling is analyzed with relevant theories and assumptions through FISH language programming in FLAC3D, which originally only has the solid-fluid two-phase coupling function. The prediction of harmful gas eruptions in shield construction is realized. On this basis, a set of real-time monitoring systems for the harmful gases is constructed, which realizes staff evacuation warnings. The research achievement has been successfully applied in a practical project.