Abstract: The shallow gas with a certain pressure is found in depths of 15-35 m in many sections of Hangzhou Metro Line No.1 during the detailed exploration. It not only constitutes a threat to the safety of investigation, but also influences the normal construction of the metro structures. It will be a threat to the later operation of metro if unsuitable prevention and control countermeasures are adopted. Shallow gas is one of the challenges met in construction of Hangzhou Metro Line No.1. However, at present, the case study with such large scale shallow gas is few in the history of metro construction at home and abroad; and the methods for preventing shallow gas disaster and the experiences are quite limited. Based on the studies of engineering properties of shallow gas and soil containing gas in Hangzhou area, considering the characteristics of Hangzhou metro engineering in different construction stages, and combining the practical engineering experience and the results of laboratory test and field monitoring, some pertinent disaster countermeasures are proposed. The countermeasures may supply assistance to metro construction and later operation, and also can give a reference to underground constructions in similar areas.

Key words: shallow gas, Hangzhou metro, disaster prevention and control