This paper proposes a new siphon drainage method for treating the leakage of tunnels under operation.A series of physical model experiments were carried out to analyze the influence of siphon drainage action on the groundwater in the surrounding rock masses of the tunnel.The results show that siphon drainage system has a significant influence on the distribution of groundwater level

especially at the location of siphon pipe installation.Rainfall intensity is one of the most important factors that affect the discharge capacity of the siphon drainage.When the rainfall intensity increases

the discharge amount of siphon drainage increases very fast at the beginning and then is kept at its maximum flow rate.Meanwhile

it requires more time to drain off all infiltrated rain water.Furthermore

the permeability coefficient of surrounding rock and the siphon pipe diameter are the two other influence factors that determine the distribution of groundwater level and the effect of siphon drainage.When the permeability coefficient of surrounding rock and the siphon pipe diameter are both relatively larger

the drawdown of the groundwater level is also larger

the duration of steady siphon drainage at the maximum flow rate becomes shorter and the time required to drain off all the rain water is also shorter.Therefore

the effect of the siphon drainage is quite good in such situation.