Abstract: To analyse the mechanism of coal-gas outbursts, a one-dimensional flow model is established. A break-start criterion of coal, as a basic criterion of outbursts, is given. In this ideal model, the tectonic pressure before excavation, as a load on coal mass, affects break-start and then the flow field. The flow field is decoupled with the stress field of coal, so that the gas seepage, the break-start of coal and the consequent two-phase flow, and pure gas flow, can be analysed independently of the stress fiel...